IV. MISCELLANEOUS EXAMINATIONS. DETERMINATION OF THE NATURE AND COLOR OF THE HAIR AND BEARD. A criminal, in order to conceal his identity, may change the color of the hair and beard by artificial means; either to a darker shade, in case they were naturally of a light color, or, to a lighter hue, if they were originally dark, and the chemical expert may be called upon to detect this artificial coloration, and restore the original color of the hair. It may also happen, that portions of hair still adhere to the clots of blood sometimes found on an instrument which has been employed in the commission of a crime, and consequently the question may arise as to the nature of the hair, whether it be human or animal. DETERMINATION OF THE COLOR OF THE HAIR AND BEARD.The mode of examination necessary when the hair has been blackened is different from that used when it has been decolorized. The hair has been blackened.As various methods of dyeing hair black are in use, the means of restoring the original color differ. The following are the methods most usually employed in dyeing: 1º. The hair is well rubbed with a pomade, in which finely pulverized charcoal is incorporated. This preparation, which is sold under the name of "mÉlaÏnocome," possesses the disadvantage of soiling the fingers and clothing, even for several days after its application. 2º. The hair is moistened with a dilute solution of ammonia, and a perfectly neutral solution of a bismuth salt (chloride or nitrate) is then applied. It is subsequently washed, and allowed to remain in contact with a solution of sulphuretted hydrogen. 3º. The same operation is performed, a lead compound being substituted for the bismuth salt. 4º. A mixture of litharge, chalk, and slacked lime is applied, and the head covered with a warm cloth. The hair is afterwards washed, first with dilute vinegar, then with the yolk of an egg. 5º. The hair is first cleansed with the yolk of an egg, and then moistened with a solution of plumbate of lime; or, 6º. It is moistened with a solution of nitrate of silver, to which a quantity of ammonia sufficient to dissolve the precipitate first formed has been added. The first method merely causes a mechanical admixture of a coloring matter with the hair. In the four succeeding processes, a black metallic sulphide is produced; either by the subsequent application of a solution of sulphuretted hydrogen, or by the action of the sulphur normally present in the hair. In the last method, the formation of sulphide of silver doubtless occurs; but the principal change that takes place is probably due to the action of light, which, as is well known, decomposes the salts of silver. In order to restore the original color to hair which has been treated with "mÉlaÏnocome," it is only necessary to dissolve in ether the fatty matters present, and then remove the charcoal by washing with water. In case the hair has been dyed by means of a bismuth or lead salt (as in methods 2, 3, 4 and 5), it is immersed for several hours in dilute hydrochloric acid: the metal present dissolves, as chloride, and the original color of the hair is rendered apparent. It then remains to detect the metal dissolved in the acid solution, in order to establish, beyond doubt, the fact that a dye has been employed. This is accomplished by means of the methods used for the detection of metals in cases of supposed poisoning. If, finally, an ammoniacal solution of nitrate of silver has been employed to cause the coloration, the hair is immersed, for some time, in a dilute solution of cyanide of potassium, and the fluid subsequently examined for silver. In case a portion of the salt has been converted into the sulphide, it will be difficult to restore the original color, as the removal of this compound is not easily effected. The hair has been decolorized.Black hair can be bleached by means of chlorine-water, the various shades of the blonde being produced by the more or less prolonged action of the reagent. In this case, the odor of chlorine is completely removed only with great difficulty, and the hair is rarely uniformly decolorized. DETERMINATION OF THE NATURE OF THE HAIR.In examinations of this character use is made of the microscope. The hair to be examined is suspended in syrup, oil, or glycerine and placed between two thin glass plates. Human hair is sometimes cylindrical; sometimes flattened. It consists either of a central canal, or of a longitudinal series of oblong cavities which contain oily coloring matter, and possesses the same diameter throughout its entire length. The brown hair of the beard and whiskers, medium-sized chestnut hair, the hair of a young blonde girl, and the downy hair of a young man possess respectively a diameter of 0.03 to 0.15; 0.08 to 0.09; 0.06; and 0.015 to 0.022 millimetres. These exhibit on the surface slightly projecting scales, which are irregularly sinuous at the border, separated from each other by a space of about 0.01 m.m., and are transparent, whatever may be their color. The hair of ruminants is short and stiff, and is characterized by containing cavities filled with air. Wool, however, The hair of the horse, ox and cow never exceeds 12 m.m. in length, and is tapering, its diameter gradually diminishing from the base. It is perfectly opaque, and does not appear to possess a central canal; has a reddish color, and frequently exhibits lateral swellings, from which small filaments occasionally become detached, in the same manner as a twig separates itself from the parent branch. EXAMINATION OF FIRE-ARMS. |
BARREL DRIED NEAR A FIRE. | UNWASHED BARREL. | |
---|---|---|
After 1 day | slight reddish yellow color | greenish yellow color. |
— 2 or 3 days | a little darker " | reddish-brown " |
— 4 days | a redder" | reddish-brown " |
— 5 or more days | a rusty-red" | rusty-red " |
THE GUN IS NOT PROVIDED WITH A FLINT LOCK.
At present weapons having flint-locks have almost entirely gone out of use and have been superseded by the ordinary percussion gun; these latter, in turn, are being gradually replaced by breech-loaders, charged with or without a metallic cartridge. The indications obtained in the preceding examinations by means of the fire-pan, will therefore disappear; the results given by the inspection of the barrel may possibly hold good. In regard to breech-loaders, all the useful indications furnished by the coloration of the wadding and powder fail to occur; the latter being enclosed either in a paper cylinder or in a copper socket.
The fact that gun cotton and white gunpowder are occasionally made use of, adds to the difficulty of obtaining reliable results by the mere inspection of a weapon. White gunpowder does not oxidize the gun, fails to give rise to any salt of iron, and possesses a white color; gun-cotton produces distinctive indications varying with its purity. Owing to these facts, it is evident that the method proposed by M. Boutigny is of no real
DETECTION OF HUMAN REMAINS IN THE ASHES OF A FIRE-PLACE.
This class of examinations is particularly necessary when the crime of infanticide is suspected. As the complete incineration of a cadaver is a long and difficult operation, it frequently occurs that bones—partially or completely carbonized, but retaining their original form—are discovered by the careful examination of the ashes of the fire-place in which the combustion was accomplished.
When this is not the case and complete incineration and disaggregation have occurred, recourse must be had to the indications furnished by a chemical analysis. These indications are reliable, however, only when the certainty exists that bones of animals have not been consumed in the same fire-place; otherwise, the results obtained are entirely worthless, the reactions given by ashes of animal bones being identical with those produced by the ashes of a human body. Two tests are employed to detect the presence of bones in the residue left by the combustion of animal matter.
1. A portion of the ashes is placed in a silver crucible, heated with potassa, and the mass afterwards treated with cold water. If animal matter is contained in the consumed materials, cyanide of potassium will be present in the aqueous solution. In order to detect this salt, the fluid is acidulated with hydrochloric acid, and a solution of persulphate of iron added: the formation of a blue precipitate indicates the presence of the cyanide.
2. The ashes are next examined for phosphate of lime. As wood, coal, and the other substances usually employed for heating purposes contain none or little of this salt, its detection in a notable quantity would lead to the inference that bones have been consumed. The ashes are allowed to digest for twenty-four hours with one-quarter of their weight of sulphuric acid. Water is next added to the pasty mixture, and the fluid filtered. If phosphate of lime be present, it is converted by this treatment into a soluble acid phosphate, which passes into the filtrate. Upon adding ammonia to the filtrate, a precipitate of neutral phosphate of lime is formed, neutral phosphate of ammonia remaining in solution. The fluid is again filtered, the filtrate acidulated with nitric acid, and then boiled with a solution of molybdate of ammonia likewise acidulated with nitric acid: in presence of a phosphate, a yellow precipitate, or at least a yellow coloration of the fluid, will be produced. It has been stated that the disengagement of sulphuretted hydrogen, upon treating the ashes with sulphuric acid, is an indication that the combustion of a human body has occurred; this reaction is, however, valueless, inasmuch as coal and certain vegetable ashes likewise evolve the gas when subjected to the same treatment.
Contracts, checks, etc., are frequently altered with criminal intent, either by erasing the portion of the writing over the signature and substituting other matter, or by changing certain words, in order to modify the signification of a sentence.
Writings are altered either by erasure or by washing. Erasure, although more easily executed, is seldom employed,
In case washing by means of chlorine has been resorted to, the sizing—which renders the paper non-bibulous, and which is only with difficulty replaced—may have been removed. Formerly paper was sized by immersion in a solution of gelatine; at present, however, a soap of resin, or wax, and alumina (a little starch being added) is more commonly used. In the latter case, the sizing is less easily removed by the action of water than when the gelatine preparation is employed; the detection of its attempted restoration is also a matter of less difficulty, as gelatine would be employed for this purpose, and this body possesses properties different from those exhibited by the substances normally contained in paper: iodine, for instance, which imparts a yellow color to gelatine, turns starch violet-blue. In order to detect the alteration of a writing, the following examinations are made:
1º. The paper is carefully examined in all of its parts, and in various positions, by aid of a lens. In this way, either thinned points, caused by erasure, or remaining traces of words, may possibly be discovered.
2º. The paper is next placed upon a perfectly clean piece of glass, and completely and uniformly moistened with water. The glass is then removed, and the transparency of the paper examined by aid of a lens. When uniform transparency is exhibited, and certain portions are neither more transparent nor more opaque than the rest of the paper, it is probable that erasure has not been attempted. If, on the other hand,
3º. The paper is dried and the above operation repeated with alcohol of 87 per cent. Indications may now be observed which failed to occur in the treatment with water; as well as these latter confirmed. As alcohol dissolves sandarac, the points that formerly appeared opaque may now become transparent.
4º. The paper is again dried, then placed under a sheet of very thin silk-paper, and a warm iron passed over it. This operation frequently causes the reappearance of words that have been partially obliterated. It is also advisable—as suggested by M. Lassaigne—to expose the paper to the action of iodine vapors. If alteration has not been attempted, the paper will acquire an uniform color; yellow, if sized with gelatine; violet blue, if sized with the mixture of soap, resin and starch. When, on the contrary, a subsequent sizing of gelatine has been applied in order to mask the alteration—the paper having been originally sized with the above mixture—it will assume in some portions a yellow, in others a violet-blue color.
5º. It is ascertained whether the paper possesses an acid reaction. If so, its acidity may result from the presence of hydrochloric acid, in case the paper was washed with chlorine, or of other acids. Alum, used to disguise erasure, would also cause an acid reaction. The mere detection of acidity is, in itself, of little importance, as, in the manufacture of paper, the pulp is bleached by means of chlorine, and this reagent may not have been entirely removed by washing. If, however, the paper is
6º. The manuscript under examination is again spread upon a glass-plate, and a solution of tannin (or preferably, a solution of ferrocyanide of potassium containing one per cent. of the salt, and acidulated with acetic acid) applied by means of a brush. If the original writing was executed with ordinary ink (which has as its base tannate of iron), and the washing has been but imperfectly performed, it is quite possible that a blue coloration will be produced by the action of the ferrocyanide. It is, however, often necessary to apply the above reagents several times before the original writing becomes apparent; indeed, in some cases months have elapsed before the reaction has occurred.
In case the alteration or destruction of the document is feared in the above test, it is well to previously provide the court with a certified copy, and then proceed with the examination.
7º. If the paper possesses a friable appearance, it has possibly been washed with sulphuric acid. This property may however originate from other causes, and the presence of the acid should be confirmed by washing the document with distilled water, and adding a solution of chloride of barium to the washings. The precipitate should form in a considerable quantity, as a slight cloudiness could be due to sulphates contained in the water used in the preparation of the pulp.
If much sulphuric acid be present, it may be so concentrated by heating as to cause the carbonization of the paper.
8º. It is also well, should washing with sulphuric acid be suspected, to ascertain, by aid of a lens, if the filaments on the surface of the manuscript possess an inflated appearance. This would be caused by the escape of carbonic acid, originating from the action of sulphuric acid upon the carbonates contained in the water used in the manufacture of the paper.
9º. Old ink is more difficult to remove than new, and it is therefore sometimes possible to cause the reappearance of old writings, over which words have been subsequently written. For this purpose, a solution containing 50 per cent. of oxalic acid is applied with a fine brush over the suspected points. As soon as the ink disappears, the acid is immediately removed by washing with water, and the paper dried. Upon now repeating the operation, the presence of a former writing may be detected after the complete disappearance of the words last written.
10º. According to M. Lassaigne, when the same ink has not been used throughout a document, washing with dilute hydrochloric acid will demonstrate the fact. This acid, while causing the gradual obliteration of characters written with ordinary ink—the shade of the paper not being altered—produces a red color, if ink containing log-wood has been employed, and a green coloration, in case the ink used contained Prussian blue.
The expert may possibly be called upon to give evidence as to the existence of a "trompe-l'oeil;" as was the case in the trial of M. de Preigne, which took place at Montpelier in 1852. A "trompe-l'oeil" consists of two sheets of paper, glued together at the edges, but having the upper sheet shorter than the other which therefore extends below it. This species of fraud is executed by writing unimportant matter on the
Numerous means have been proposed, in order to render the falsification of documents a matter of difficulty. The most reliable of these is the use of "Grimpe's safety-paper," containing microscopic figures, the reproduction of which is impossible. Unfortunately, up to the present, the government has adopted methods less sure.
EXAMINATION OF WRITINGS IN CASES WHERE A SYMPATHETIC INK HAS BEEN USED.
Sympathetic inks are those which, although invisible at the time of writing, become apparent by the application of certain agents. They are of two classes: those which are rendered visible by the mere application of heat, such as chloride of cobalt, or the juice of onions; and those which are brought out only by the action of a reagent. The inks of the second class most frequently used are solutions of acetates of lead, and other metals which give a colored sulphide when treated with sulphuretted hydrogen. Characters written with a solution of ferrocyanide of potassium acquire a blue color, if
When the presence of characters written with a sympathetic ink is suspected, the document is examined as follows:
1. The paper is at first warmed: if the ink used is of the first class, the characters will now become legible; otherwise the examination is continued as below.
2. The paper is exposed to the action of steam, in order to moisten the ink present (care being taken to avoid dissolving the characters), and a current of sulphuretted hydrogen allowed to act upon it. If the ink used consists of a lead, bismuth, or gold salt, a black coloration will ensue; if salts of cadmium or arsenic were employed, the characters will acquire a yellow color; if, finally, a salt of antimony was used, a red coloration will be produced.
3. If no coloration was caused by the action of sulphuretted hydrogen, it is probably that either a solution of ferrocyanide of potassium or a persalt of iron has been resorted to. Each of these solutions is separately applied on a small portion of paper by means of a brush, and notice taken if the characters become visible. The solution that produced the change is then applied over the entire sheet.
4. In case only negative results were obtained in the preceding operations, it must not yet be concluded that a sympathetic ink has not been used, although we are left without further recourse to chemical tests. Numerous organic compounds may have been resorted to, the detection of which is almost impossible; moreover, if a mistake was made in regard to the preparation supposed to have been used, the reagents employed for its detection may render the discovery of another ink absolutely impossible. It is therefore often neces
FALSIFICATION OF COINS AND ALLOYS.
In all civilized countries a fixed standard for coins and precious alloys is established by law, in order to prevent the perpetration of frauds which would be of serious injury to the public welfare. The substitution of coins consisting of an alloy inferior in value to the standard fixed by law, is too advantageous a fraud not to be often attempted.
Coins are most frequently altered by clipping; by stuffing, that is, by boring the coin and inserting an alloy of small value; by doubling, which operation consists in covering its face with two thin laminÆ taken from a genuine coin; and by applying a coating of gold or silver by means of electro-plating.
In order to ascertain if a coin has been counterfeited, its weight should at first be determined. If it has been clipped, or consists of an alloy possessing a density less than that of silver or gold, the fact is immediately demonstrated by its decreased gravity.
The coin is further tested by throwing it down upon a hard substance: gold and silver give a ringing sound, whereas the majority of other metals produce a dull sound.
The result obtained by this latter test often fails to be reliable. A skilful counterfeiter may prepare an alloy equally sonorous and heavy as silver or gold; in fact, M. Duloz exhibited to the author an alloy, prepared by him, possessing the density, sonorousness and lustre of silver; the composition of which, for obvious reasons, has not been published.
In instances of this nature the fusibility of the coin should be determined, and the result obtained compared with the melting point of the legal alloy, or, this failing, a chemical analysis executed. In order to perform the latter test, the coin under examination is boiled with nitric acid: all metals are dissolved, with exception of gold and platinum, which remain unaltered, and tin and antimony, which are converted respectively into metastannic and antimonic acids. The fluid is filtered, the insoluble residue well washed, and then boiled with hydrochloric acid, which dissolves the metastannic and antimonic acids. The solution is again filtered, and the second residue dissolved in aqua regia. The metals dissolved in the several filtrates are then detected, either by the processes previously given for the detection of metallic poisons, or by the more complete methods contained in works on chemical analysis. This qualitative test is, however, insufficient, in case the falsification consisted in merely diminishing the proportions of the valuable metals contained in the alloy, without changing its qualitative composition: it is then necessary to execute a quantitative estimation of the metals present. As this operation requires considerable practice and the methods employed are to be found in all treatises on quantitative analysis, we will not reproduce them here.
EXAMINATION OF ALIMENTARY AND PHARMACEUTICAL SUBSTANCES.
We will next enumerate the methods employed in the detection of the principal adulterations to which flour, bread, oils of seeds, milk, wines, vinegar and the sulphate of quinine are subjected. These researches, united with those preceding, fail to embrace all the diverse examinations which the chemical expert may be expected to execute; but we do not claim to foresee all the contingencies that may arise, and will describe the steps to be pursued in instances which are anticipated, at the same time indicating general methods applicable to cases not here included.
FLOUR AND BREAD.
The adulterations to which flour and bread are exposed usually consist in adding damaged or an inferior grade of flour to wheaten flour, or in disguising the presence of a poor quality of flour by the addition of mineral substances, such as: plaster, chalk, lime, alum, and sulphate of copper.
Good flour has a white color, possessing a slightly yellow tinge, but is entirely free from red, grey or black specks. It is soft to the touch and adheres to the fingers, acquiring, when compressed in the hand, a soft cushion-like form. If mixed with water, it forms an elastic, homogeneous, but slightly coherent dough, which can be extended out in thin layers.
Flour of an inferior quality possess a dull white color, and does not assume the cushion-like condition mentioned above, when pressed in the hand, but escapes between the fingers: the dough formed is of a poorer quality.
Flour which has been damaged by moisture has a dull or
The constituents of pure flour are:
- Gluten.
- Starch, in the proportion of 50 to 75 per cent.
- Dextrine, in the proportion of several per cent.
- Glucose, in the proportion of several per cent.
- Salts, remaining in the ash obtained by the calcination of the flour, in a proportion not exceeding 2 per cent.
- Water, of which it loses 12 to 15 per cent., at the heat of a water-bath, and 15 to 20 per cent., at a temperature of 160°.
- Bran, (ligneous and fatty matter,) in a very small proportion, when the flour has been properly bolted.
In the process of bread-making, the gluten undergoes fermentation by the action of the leaven and liberates carbonic acid, which causes the dough to become porous and swell up, or, as it is termed, to rise. Bread contains the same substances as flour, but gluten and starch are present in a state that does not admit of their separation by mechanical means, and glucose, if present at all, exists in a smaller quantity: the proportion of dextrine and water is, on the other hand, considerably increased. The bread of the Paris city bakeries contains 40 per cent. of water—the crumb, which forms 5/6 of the weight of the bread, containing 45 per cent.; the crust, which constitutes the remaining 1/6, containing 15 per cent. In army bread 43 per cent. of water are contained—the crumb, which constitutes 4/5 of the weight of the bread, holding
The addition of common salt naturally increases the proportion of ash left upon calcining bread.
Water is contained in stale bread in the same quantity as in fresh bread; but exists in a modified molecular condition: upon heating stale bread, it acquires the properties of fresh bread.
The following substances are used in the adulteration of wheaten flour:[P]
- Potato-starch.
- Meals of various grains (rice, barley, corn, oats and rye).
- Vegetable meals, (beans, horse-beans, kidney-beans, peas, vetch, lentils, etc.).
- Darnel meal.
- Buckwheat flour.
- Linseed-meal.
- Mineral substances (plaster, chalk, lime, alum, and sulphate of copper).
In order to detect these substances, the gluten, the starch, and the ash are separately examined.
a. EXAMINATION OF THE GLUTEN.
In order to separate the gluten, two parts of the flour to be examined and one part of water are mixed into a paste,
Gluten prepared from a mixture of equal parts of wheat and rye is adhesive, blackish, without homogeneousness, spreads out more readily than pure wheaten gluten, separates easily and adheres somewhat to the fingers.
Gluten obtained from a mixture of wheat and barley is non-adhesive, of a dirty reddish-brown color, and appears to be formed of intertwined vermicular filaments.
Gluten formed from a mixture of equal parts of wheat and oats has a blackish-yellow color and exhibits, at the surface, numerous small white specks.
The gluten from a mixture of wheat and corn has a yellowish color, is non-adhesive, but firm, and does not readily spread.
Gluten prepared from a mixture of wheat and leguminous flour is neither cohesive nor elastic, and, if the proportion of the latter present be considerable, can be separated and passed through a sieve, like starch.
The gluten obtained from a mixture of equal parts of wheat and buckwheat flour is very homogeneous, and is as easily prepared as the gluten from pure wheaten flour. It possesses when moist a dark-grey color; which changes to a deep black upon drying. The proportion of gluten in flour is exceedingly variable: good flour contains from 10 to 11 per
b. EXAMINATION OF THE STARCH.
The washings of the flour are allowed to stand for some time in a conical-shaped vessel. As soon as the amylaceous matter has entirely settled to the bottom of the vessel, the greater portion of the water is decanted, and the residual mass brought upon a small filter and allowed to dry. The residue is then examined for potato and rice starch.
Potato starch. The grains of potato starch are much larger than those of wheaten starch. If a portion of the residue mentioned above is crushed in an agate mortar, the granules of potato starch present are ruptured, and their contents liberated; the wheaten starch remaining unaltered. The mass is then taken up with water, and the fluid filtered. If potato starch be present, the filtrate will acquire a blue color upon addition of an aqueous solution of iodine; otherwise, a yellow or violet-rose coloration is produced. It is necessary to avoid crushing the residue for too long a time, as the granules of wheaten starch would also become ruptured by prolonged comminution.
Besides the difference presented by potato starch in the size of the granules in comparison to those of wheaten starch, the former swell to ten or fifteen times the volume of the latter, when treated with a solution of potassa: wheaten starch granules are not affected by the treatment, if the solution used does not contain more than 2 per cent. of the salt. The results obtained by the above operation should be confirmed by a microscopic examination.
A portion of the residue is moistened with solution of iodine, then carefully dried, and placed on the slide of a microscope. The mass is next moistened with a solution containing 2 per cent. of potassa, and examined. The addition of iodine causes the potato starch granules to acquire a blue color, and renders their shape and volume more easily perceptible; thus allowing the two varieties of starch to be readily distinguished. Fig. 13 represents the relative size of the granules as observed under the microscope.[Q]
The presence of potato starch in bread is also detected by crushing a small portion of the sample under examination on the glass, and then adding a few drops of the alkaline solution.
MISCELLANEOUS TESTS.
Linseed and rye meals.—If linseed meal is moistened with an aqueous solution containing 14 per cent. of potassa and examined under the microscope, numerous minute characteristic granules, smaller than the grains of potato-starch, are observed. These possess a vitreous appearance, sometimes a reddish color, and usually form in squares or very regular rectangles. The test is equally applicable to bread. The detection of linseed and rye meals is simultaneously effected by exhausting the suspected flour with ether, then filtering the solution and allowing it to evaporate. If the flour contains rye, the oil left by the evaporation, when heated with a solution of mercury in concentrated nitric acid, is converted into a solid substance having a fine red color; but it remains unaltered, if entirely due to linseed. In case the oil becomes solidified, the mercury salt present should be removed by washing with water, the residue taken up with boiling alcohol of 36° B. and the solution filtered: upon evaporating the alcoholic filtrate, a residue is obtained consisting of the linseed oil present.
Buckwheat.—Flour adulterated with buckwheat is less soft to the touch, does not pack as easily, and passes more readily through a sieve than pure wheaten flour. It presents, here and there, blackish particles, due to the perisperm of the grain, and has a dirty-white color. As previously remarked, the gluten obtained from a mixture of buckwheat and wheaten flour possesses a grey or even a black color. The starch furnished by buckwheat flour exhibits polyhedral agglomerations, analogous to those presented by corn.
Darnel.—The use of darnel in the adulteration of wheaten flour may give rise to serious sanitary results. To effect its
Legumens.—Leguminous meals cannot be added otherwise than in small proportions to wheaten flour, owing to the rapidity with which they change the properties of the latter, and communicate to it their characteristic odor—noticeable upon treating the flour with a little boiling water. Their presence is also easily detected by the distinctive properties of the vegetable itself, and by the appearance of the amylaceous residue in the microscopic examination. In order to decide as to the presence of legumens, the washings containing the starchy matter of the flour, after the particles of gluten present have been separated by passing the fluid through a silk sieve, are divided into two portions. One portion is allowed to undergo fermentation, at a temperature of 18° to 20°: in case leguminous substances are not present, lactic fermentation occurs and the odor of sour milk is alone perceptible; if, on the other hand, legumens are contained in the fluid, rancid fermentation takes place, and an odor is emitted resembling that of decayed cheese. The remaining portion of the washings, after being decanted from the residue of amylaceous matter, is filtered and evaporated until a yellowish translucent pellicle appears upon its surface. The fluid is then again filtered from the coagulated albumen common to all flours, and the legumin
The leguminous deposit produced appears white and flaky; when examined under the microscope, it presents lamilla emarginated at the border; it is odorless and tasteless; when dried, it assumes a horny appearance; it is insoluble, both in water and alcohol, and does not become gelatinous when treated with boiling water; it is readily soluble in potassa and other alkaline solutions, from which it is precipitated upon addition of nitric, hydrochloric, acetic, oxalic, and citric acids; upon protracted boiling in water, it loses its property of being soluble in ammonia. The above tests having been applied, the residue containing the starch is next examined. For this purpose, a small portion is moistened with a little water, a few drops of iodine solution added, and the mixture placed on the side of the microscope: the bluish grains contained in the polyhedral and cellular envelope (Fig. 15) are easily recognized. The mixture on the glass may also be treated with an aqueous solution of potassa (containing 10 per cent. of the salt), or with dilute hydrochloric acid: these reagents dissolve the starch present, leaving the reticulated tissue intact. Should this examination fail to give a definite result, the remaining portion of the amylaceous residue is subjected to a sort of levigation, and the part most slowly deposited separated. In this portion the reticulated tissues of the leguminous substances present are contained, and, as they are comparatively free from foreign matters, their identification is a matter of comparative ease. In case the presence of reticulated tissue is indicated, it is still necessary to apply confirmatory chemical tests.
Meals prepared from beans, horse-beans, and lentils, contain a tannin which imparts a green or black color to salts of iron. The coloration is rendered very sensitive if a rather considerable quantity of the flour to be examined is passed through a silk sieve, and the remaining bran treated with a solution of sulphate of iron (ferrico-ferrous sulphate): the reaction immediately occurs, even if the sample contains but 10 per cent. of bean meal. The meals of horse-beans and of vetches acquire a red color, when exposed to the successive action of nitric acid and of ammonia vapors. In order to apply this test, the suspected flour is placed upon the edge of a capsule containing nitric acid, the latter heated, and, as a yellow coloration appears, the acid removed and replaced by ammonia. The capsule is then set aside: if the flour is adulterated with either of the above vegetables, reddish spots, which are easily perceptible by aid of a magnifying glass, are soon produced.
In case bread is to be examined, it is exhausted with water, the fluid passed through a sieve, the upper layer decanted, then evaporated, and the residue taken up with alcohol. The tincture so obtained is evaporated, and the second residuum treated with nitric acid and ammonia, as directed above. When meals prepared from beans, vetches, or lentils are heated on a water-bath with hydrochloric acid, diluted with three to four times its volume of water, a cellular tissue, possessing the color of wine-dregs, remains behind; flours of wheat, peas, and kidney-beans leave a colorless residue, when subjected to the same treatment.
Finally; the grains of the starch (fecula) of legumens possess a volume about equal to that of potato granules, and exhibit either a longitudinal furrow in the direction of their longer axis, or a double furrow arranged in a star-like form.
c. EXAMINATION OF THE ASH.
Leguminous substances, and more particularly mineral salts, are detected by the examination of the ash left upon the incineration of the flour.
Detection of Legumens.—Pure wheaten flour furnishes an ash consisting of about 2 per cent. of its weight; whereas meals of legumens leave from 3 to 4 per cent. of their weight in ash. This difference is, however, too slight to furnish conclusive results; the analysis of the ash is also necessary. The ash of wheaten flour is non-deliquescent, dry, semi-fused, and chiefly consists of phosphates of potassa, soda, magnesia and lime, of sulphates, and of silica. The solution obtained by treating the ash with water has an alkaline reaction. The phosphates of the alkalies, present in the ash of wheat, exist in the state of pyrophosphates, and, as chlorides are absent, the addition of nitrate of silver to the aqueous solution of the ash produces a white precipitate, consisting entirely of pyrophosphate of silver, which is not affected by exposure to the light.
The ash of leguminous meals is deliquescent and soluble in water, forming a strongly alkaline solution, which contains both chlorides and neutral phosphates. The latter give a clear yellow precipitate with nitrate of silver. Upon adding a solution of this salt to the aqueous solution of the ash, a pale yellow precipitate, which turns violet if exposed to the light, is therefore produced.
Detection of mineral substances.—The principal mineral substances, that are fraudulently added to flour, are ground calcined bones, sand, lime, plaster, alum, and sulphate of copper. The two last named salts are almost invariably added in small quantities; alum renders the flour white, even when used in the proportion of one per cent.; sulphate of copper is added
a. Ground bones (carbonate and phosphate of lime).—The washings of the gluten are placed in a conical vessel, and, after some time has elapsed, the clear supernatant fluid is removed by means of a syphon, a conical shaped deposit remaining on the bottom of the vessel: two hours later, the fresh layer of fluid that has formed is removed with a pipette. As soon as the residue becomes nearly solid, it is detached from the vessel, placed upon a fragment of plaster, and allowed to dry. The bones, being heavier than the amylaceous substances, are to be found in the apex of the cone formed by the residue. This is detached, and incinerated: in case the ash obtained contains phosphate and carbonate of lime, the addition of hydrochloric acid will cause effervescence, and, upon adding ammonia to the acid solution, a white precipitate will be formed. If the solution is then filtered and oxalate of ammonia added to the filtrate, a precipitate will be produced which, when heated to redness, leaves a residue of caustic lime possessing an alkaline reaction.
b. Sand.—As this substance possesses a much greater specific gravity than the usual constituents of flour, it is only necessary, in order to accomplish its separation, to repeatedly stir the flour with water, and remove the deposit at first formed, which, if consisting of sand, will be insoluble in acids, and will grate, when placed between the teeth.
c. Carbonates of lime and magnesia; vegetable ashes.—Carbonic acid is always evolved, upon treating flour with hydrochloric acid. If the base present be calcium, upon adding oxalate of ammonia to the filtered solution—which has previously been neutralized with ammonia—a white precipitate, possessing the properties mentioned above, will be formed; in case
d. Lime.—In presence of lime, carbonic acid produces a white precipitate, when conducted into the filtered aqueous extract of the flour.
f. Alum.—A portion of the flour to be examined is treated with water, the fluid filtered, and the filtrate divided in two portions: in one, sulphuric acid is detected by means of chloride of barium; in the other, alumina by adding a solution of potassa, which gives with its salts a white gelatinous precipitate, soluble in an excess of the reagent.[R]
g. Sulphate of copper.—About 200 grammes of the bread under examination are incinerated; the ash treated with nitric acid; the mixture evaporated until it acquires a sticky consistence, and the mass then taken up with water. The aqueous solution is next filtered; an excess of ammonia and several drops of solution of carbonate of ammonia added; the fluid again filtered, the filtrate slightly acidulated with nitric acid, and divided into two parts. It is then ascertained if sulphuretted hydrogen produces in one portion of the solution a brown precipitate of sulphide of copper, and if solution of ferrocyanide of potassium produces in the other a reddish-brown precipitate of ferrocyanide of copper.[S]
FIXED OILS.
Olive oil designed for table use is frequently adulterated with the oils of poppy, sesamÉ, cotton-seed, pea-nuts, and other nuts; olive oil, intended for manufacturing purposes, is often mixed with colza and nut oils.
The tests used are of a rather unsatisfactory character. In all instances, when the chemist is called upon to pronounce as to the adulteration of an oil, it is necessary to execute comparative experiments with the pure oil, and with admixtures arbitrarily prepared: it is only when this is done that the indications obtained are of value.
EXAMINATION OF OLIVE OIL INTENDED FOR TABLE USE.
a. The density of the oil is determined by means of a hydrometer (oleometer) provided with a scale giving the densities from 0.8 to 0.94, for the temperature of 15.° Pure olive oil possesses a specific gravity of 0.917; poppy oil one of 0.925; a mixture of the two, an intermediate density. Since the fixed oils are not definite chemical compounds, this test is seldom conclusive.
b. Two or three cubic centimetres of concentrated nitric acid, containing nitric peroxide in solution (or a solution of mercury in strong nitric acid), are added to the oil to be examined, as well as to a sample of pure olive oil. The two samples are then allowed to stand in a room where the temperature does not exceed 10.° The oleine of the olive oil is converted into solid elaidine, and the mixture after some time becomes sufficiently thick to remain in the vessel upon inversion. If the sample under examination is free from adulteration, it will solidify at the same time as the pure oil; whereas, the presence of one per cent. of poppy oil, or of other drying oils, suffices to retard the solidification for forty minutes.
c. Fifteen grammes of the oil are mixed in a glass vessel with the same amount of strong sulphuric acid, the temperature of the two liquids being previously observed. The mixture is stirred with a thermometer, and the maximum temperature noted: pure olive oil produces an elevation of temperature of 37.°7; pure poppy oil, an elevation of 70.°5; and a mixture of the two an elevation of temperature intermediate between 37.°7 and 70.°5.
d. One volume of nitric acid of sp. gr. 1.33 is agitated with 5 grammes of the oil, and notice taken of the coloration produced after the lapse of five minutes. If the olive oil is pure, it acquires a pale green color; in case it is mixed with sesamÉ or nut oil, a deep-red color appears: poppy oil also communicates a reddish coloration, but one less deep than the preceding.
If an acid of sp. gr. 1.22 is taken, it is still less difficult to distinguish between sesamÉ, nut and poppy oils; the latter assumes, in this case, a pale yellowish-red color.
Pea-nut oil fails to exhibit a coloration; but can be recognized by its conversion into a white solid, when mixed with 1/5 of its volume of a solution of caustic soda of sp. gr. 1.34.
EXAMINATION OF OLIVE OIL INTENDED FOR MANUFACTURING PURPOSES.
The chief adulterations are colza and nut oils. The latter is detected by means of the reaction with nitric acid, as described above. Colza oil is recognized by mixing 5 volumes of the sample to be examined, with 1 volume of sulphuric acid of sp. gr. 1.655: if colza or nut oils are present, a brown coloration ensues; under the same circumstances, pure olive
EXAMINATION OF HEMPSEED OIL.
This oil is frequently adulterated with linseed oil. The reactions exhibited by these oils are nearly identical, and the detection of the admixture is extremely difficult. It is advisable to mix the suspected oil with sulphuric acid, notice being taken of the elevation of temperature produced, and to treat it with nitric acid and with dilute potassa solution, subjecting, at the same time, an artificial mixture of the two pure oils to the same treatment, and comparing the results obtained.
TEA AND ITS ADULTERATION.
Among alimentary substances probably no article is subjected to more adulteration than tea. The sophistications practised may be conveniently divided into three classes:
1. Additions made for the purpose of giving increased bulk and weight, which include foreign leaves and exhausted tea-leaves, and also certain mineral substances, such as metallic iron, sand, brick-dust, etc.
2. Substances added in order to produce an artificial appearance of strength in the tea decoction, catechu, or other bodies rich in tannin, and iron salts being chiefly resorted to for this purpose.
3. The imparting of a bright and shining appearance to the tea by means of various coloring mixtures or "facings,"
Genuine tea is the prepared leaf of Thea sinensis. It contains: moisture, 6% to 10%; theine, 0.4% to 4.0%; tannin, (green) 20%, (black) 10%; ash, 5% to 6%; soluble extractive matters, 32% to 50%; and insoluble leaf, 47% to 54%.
The presence of foreign leaves, and, in some instances, of mineral adulterants, in tea is best detected by means of a microscopic examination of the suspected sample. The genuine tea-leaf is characterized by its peculiar serrations and venations. Its border exhibits serrations which stop a little short of the stalk, while the venations extend from the central rib, nearly parallel to one another, but turn just before reaching the border of the leaf (see Fig. 16). The Chinese are said to employ ash, plum, camellia, velonia, and dog-rose leaves for admixture with tea, and the product is stated to be often subjected in England to the addition of the leaves of willow, sloe, beech, hawthorn, elm, box-poplar, horse-chestnut, and fancy oak (see Figs. 17, 18, and 19). For scenting purposes chulan flowers, rose, jasmine, and orange leaves are frequently em
TEA ASSAY.
In the following tea assay proper the estimation of theine is not included. The processes suggested for this determination are rather unsatisfactory; and there appears, moreover, to exist no direct relation between the quality of tea and the proportion of theine contained. The tests here
Tannin.—A good process for the estimation of tannin in tea has been published by Allen (Chem. News, vol. xxix. p. 169 et seq.) A standard solution of lead acetate is prepared by dissolving 5 grammes of the salt in distilled water and diluting the liquid to 1,000 c.c. As an indicator, 5 milligrammes of potassic ferricyanide are dissolved in 5 c.c. of water, and an equal volume of strong ammonia-water added. The exact strength of the lead solution is to be determined by means of a solution of pure tannin of known strength. Two grammes of the tea to be tested are powdered, boiled with water, and, after filtering and thorough washing, the decoction is made up to a volume of 250 c.c.; 10 c.c. of the lead solution are now diluted with 90 c.c. of boiling water, and the tea infusion is gradually added from a burette until a few drops of the liquid, when filtered and added to a little of the indicator placed upon a porcelain slab, causes a pink coloration to appear; 125, divided by the number of c.c. of tea infusion found to be necessary to produce the pink color, will give directly the percentage of tannin in the sample examined. As previously stated, green tea contains 20% of tannin, and black tea 10%. In spent tea, however, only about 2% of tannin is present; and, although any tea deficient in this constituent could be fortified by the addition of catechu, its determination often affords indications of value.
The Ash—a. Total Ash.—5 grammes of the sample are placed in a platinum vessel and heated over a Bunsen burner until complete incineration has been accomplished.
b. Ash insoluble in water.—The total ash obtained in a is washed into a beaker and boiled with water for a considerable time. It is then brought upon a filter and the insoluble residue washed, dried, ignited, and weighed. In unadulterated tea it will not exceed 3% of the sample taken.
c. Ash soluble in water.—This proportion is obtained by deducting ash insoluble in water from the total ash. Genuine tea contains from 3% to 3.5% of soluble ash, or at least 50% of the total ash, whereas in spent or exhausted tea the amount is often but 0.5%.
d. Ash insoluble in acid.—The ash insoluble in water is boiled with dilute hydrochloric acid and the residue separated by filtration, washed, ignited, and weighed. In pure tea the remaining ash ranges between 0.3% and 0.8%; in "faced" teas, or in teas adulterated by the addition of sand, etc., it may reach the proportion of 2% to 5%. Fragments of silica and brick-dust are occasionally to be found in the ash insoluble in acid.
The Extract.—Two grammes of the carefully-sampled tea are boiled with water until all soluble matter is dissolved,
Insoluble Leaf.—The insoluble leaf obtained in the preceding operation, together with the weighed filter, is placed in an air-bath and dried for at least eight hours at a temperature of 110° C.; its weight is then determined. In unadulterated tea the amount of insoluble leaf ranges between 47% and 54%; in exhausted tea it may reach a proportion of 75%.
It should be noted that in the foregoing estimations the tea is taken in its ordinary air-dried condition. If it be desired to reduce the results obtained to a dry basis, an allowance for the moisture present in the sample (an average of 8%), or a direct determination of the same, must be made.
The following tabulation gives the constituents of genuine tea so far as the ash, extract, and insoluble leaf are involved:
- Total ash—ranges between 4.7% and 6.2%.
- Ash soluble in water—ranges between 3% and 3.5%; should equal 50% of total ash.
- Ash insoluble in water—not over 2.75%.
- Ash insoluble in acid—ranges between 0.3% and 0.8%.
- Extract—ranges between 32% and 48%.
- Insoluble leaf—ranges between 43% and 58%.
The table below may prove useful as indicating the requirements to be exacted when the chemist is asked to give an opinion concerning the presence of facing admixtures or of exhausted or foreign leaves in a sample of tea:
- Total ash—should not be under 4.5% or over 7%.
- Ash soluble in water—should not be under 40% of total ash.
- Ash insoluble in water—should not be over 3%.
- Ash insoluble in acid—should not be over 1%.
- Extract—should not be under 30%.
- Insoluble leaf—should not be over 60%.
Note.—The British Society of Public Analysts adopt:
- Total Ash (dry basis)—not over 8% (at least 3% should be soluble in water).
- Extract (tea as sold)—not under 30%.
MILK.
The chief constituents of milk are water, butter, caseine, lactose (milk-sugar), traces of albumen and mineral salts. Butter is present in the form of minute globules, held in suspension; the caseine, for the greater part, is in solution, only a small portion being present in an insoluble suspended condition. In milk only a few days old, the colostrum (the milk secreted during the first few days after parturition) consists largely of rather voluminous cellular conglomerations, containing a sufficient quantity of albumen to coagulate upon heating.
The normal density of milk is 1.030, water being 1.000; the density rising to 1.036, if the fluid has been skimmed.
Good milk contains, on an average, 3.7 per cent. of
The lactoscope possesses, however, but a limited degree of precision. M. Marchand substitutes to its use the following tests: A test-tube is graduated in three equal divisions, the upper one being subdivided into hundredths extending above, in order to determine accurately the correct volume of the fluid, expanded, as it is, by the temperature of 40°, at which the examination is executed. The first division of the tube is filled with milk, a drop, or two of strong potassa lye added, and the mixture well shaken: the second portion is then filled with ether, and the third with alcohol. The mixture is next again thoroughly agitated, and then exposed to a temperature of 40° in a water-bath. After standing for several hours, a layer of fatty matter becomes sufficiently separated to allow of measurement: but, as it contains some ether and as a small amount of butter may still be retained in the lower aqueous fluid, a correction of the results obtained is necessary. M. Marchand has compiled a table, which facilitates this correction (vide: Journ. de Pharm., Novembre 1854, and Bulletin de l'AcadÉmie de MÉdecine, Paris, 1854, xix., p. 1101).
Previously to the introduction of Marchand's apparatus, use was made of the lactometer, which consists simply of a graduated glass tube, in which the suspected milk is allowed to remain for 24 hours, at a temperature of 15°. After the lapse of this time, the cream present completely separates as a supernatant layer, the thickness of which indicates the quality of the sample taken.
M. Lacomte recommends the addition of glacial acetic acid, in order to cause the more rapid separation of the cream.
The estimation of the butter being accomplished, it is fre
Foreign substances are sometimes added to milk, for the purpose of disguising the presence of an abnormal quantity of water, the principal of which are: chalk, bicarbonate of soda, emulsion of almonds, gum tragacanth, gum arabic, starch, flour, decoction of barley or rice, sugar, and cerebral substances. These bodies are detected as follows:
Chalk.—If chalk is contained in the milk, it readily subsides upon allowing the sample to remain at rest for some time in a flask, forming a deposit which effervesces when heated with hydrochloric acid, and dissolves to a solution, in which the characteristic properties of a lime salt can be recognized.
Bicarbonate of soda.—In presence of this compound the milk possesses a strongly alkaline reaction, furnishes a serum having a sharp and bitter taste, and leaves a residue of the salt upon evaporation.
Emulsion of almonds.—The milk has a specific gravity of at least, 1.033. If it is passed through a gauze, small opaque lumps are separated. When examined under the microscope, numerous minute globules, having a diameter of 1/400 of a millimetre, are observed, and, upon adding a few centigrammes of amygdaline to one or two grammes of the milk, the characteristic odor of bitter almonds is produced.
Gum tragacanth.—When shaken in a glass flask and allowed to rest, the milk deposits on the sides small transparent lumps, which usually present a slightly elongated or angular form.
Gum arabic.—The addition of alcohol produces an abundant white opaque precipitate.
Starch, flour, decoction of barley, rice, etc.—Upon boiling the
Sugar.—If yeast is added, and the mixture allowed to stand for some time at a temperature of 30°, alcoholic fermentation ensues; under these circumstances, lactose does not undergo fermentation.
Cerebral substances.—Adulteration by these substances is probably of much less frequent occurrence than was formerly supposed. The admixture is detected by evaporating the milk to dryness, dissolving the residue in ether, evaporating the etherial solution, and fusing the second residue, which consists of fatty matters, with nitrate of potassa in a platinum crucible. The mass is then taken up with water, and chloride of barium added to the solution. If cerebral substances were contained in the milk, ether will dissolve the fatty matters present, the phosphorus of which is converted into a soluble phosphate by the calcination with nitrate of potassa and is thrown down as a white precipitate, upon the addition of a solution of chloride of barium. This test may be confirmed by a microscopic examination of the milk, when the peculiar appearance of cerebral matter will be detected.[U]
WINE.
The most common adulteration to which wines are subjected is the addition of water: wines having a rich color are frequently mixed by the dealer with lighter wines, and the fraud consummated by adding water. The detection of this adulteration is somewhat difficult, as water is a normal constituent of wine. In Paris the following method is usually employed: As soon as the wine is confiscated, it is ascer
It is also well to ascertain if two equal quantities of the prepared sample and the wine under examination require the same amount of solution of hypochlorite of lime for decolorization. In case the suspected wine has been adulterated, the quantity of hypochlorite solution used will be less than the amount necessary to decolorize the prepared wine. Foreign coloring matter may be added by the adulterator, but this fraud is easily detected by adding potassa to the sample: if its coloration is natural, a green tint is produced; whereas, if foreign matter has been introduced, the wine assumes various other colors upon the addition of the alkali.[V]
The indications furnished by the above test are rendered valueless, if the wine has been artificially colored by the addition of the coloring matter of grape-skins; but the execution of this fraud would require some knowledge of chemistry, and fortunately adulterators, as a class, are deficient in this branch of science.
Another method for detecting the addition of water is based upon the fact that fermented liquors do not contain air in solution, but only carbonic acid; whereas, water dissolves oxygen and nitrogen. It is executed as follows:
The wine to be tested is placed in a flask, the delivery-tube of which is also filled, and heated; the evolved gas being collected in a tube filled with mercury. In case the wine is pure, the disengaged gas will be completely absorbed by potassa; if, on the other hand, water has been added, an unabsorbed residue, consisting of oxygen and nitrogen, will remain.
This test is useless in case water, through which a current of carbonic acid gas has been passed for a considerable time, has been employed. Under these circumstances, however, the presence of the gas would probably be detected by the taste
It remains to mention the methods employed in determining the amount of alcohol and cream of tartar contained in wine.
The alcometrical method usually employed is based upon the difference in density possessed by pure alcohol and by mixtures of alcohol and water. Gay-Lussac has proposed an areometer (alcoholmeter), provided with a scale which directly indicates the proportion of alcohol contained in a mixture. As the indications furnished by this instrument vary with the temperature, and the scale is constructed on the basis of a temperature of 15°, a correction of the results obtained is necessary if the determination is made at other temperatures. Gay-Lussac has compiled a table which indicates at once the required correction; the following formula can also be used: x = c ± 0.4 t, where x is the quantity of alcohol present in the sample; c the degree indicated by the alcoholmeter, and t the number of degrees differing from the temperature of 15°: the second member of the formula is subtracted from, or added to the first, as the temperature at which the estimation is made is greater or less than 15°.[W]
In case the wine to be examined contains substances other than water and alcohol, which would affect its density, it is
M. Salleron offers for sale a small apparatus (Fig. 20) used in examinations of this character, consisting of a flask, closed with a gutta-percha cork, containing a tube which connects with a worm passing through a cooler. The flask is supported by an iron stand, and heated with a gas or spirit lamp.
In order to estimate the cream of tartar, the wine is evaporated to the consistency of an extract, alcohol of 82° B. added, and the residue obtained calcined in a crucible. The amount of salt present in the fused mass is then determined by the alkalimetric method, as directed in all works on quantitative analysis. The carbonate obtained from 1 gr. of cream of tartar exactly saturates 9.75 cubic centimetres of a solution
The detection of toxical substances, often contained in wine, is accomplished by the methods described under the head of detection of poisons.
VINEGAR.
Vinegar is frequently adulterated with water, and occasionally sulphuric acid is added to artificially increase its acidity.
The ordinary reagents—such as chloride of barium, or nitrate of silver—are not adapted to the direct detection of sulphuric acid, or of other mineral acids, as sulphates and chlorides, which are as readily precipitated as the free acids, may also be present.
The following method, proposed by M. Payen, is usually employed:
Five centigrammes of starch (fecula) are added to a decilitre of table vinegar, the mixture boiled for 12 or 15 minutes, and, after the fluid has become completely cooled, a few drops of iodine solution added: dilute acetic acid does not affect starch, and, in case the vinegar is pure, a blue coloration is produced; if, on the other hand, even a minute quantity of a mineral acid be present, the starch is converted into dextrine, and the addition of iodine fails to cause a blue coloration.
The water present is indirectly estimated by determining the amount of acetic acid contained in the vinegar. This can be accomplished in different ways: either the quantity of a standard solution of an alkali, necessary to exactly neutralize a measured quantity of the vinegar, is ascertained, or
SULPHATE OF QUININE.
Owing to the high price of this salt, it is frequently adulterated. The substances used for this purpose are: crystalline sulphate of lime, boric acid, mannite, sugar, starch, salicine, stearic acid, and the sulphates of cinchonine and quinidine. These bodies are detected as follows:
a. Upon slightly warming 2 grammes of sulphate of quinine with 120 grammes of alcohol of 21° B., the pure salt completely dissolves; if, however, starch, magnesia, mineral salts, or various other foreign substances are present, they are left as insoluble residues.
b. Those mineral substances that are soluble in alcohol are detected by calcining the suspected sample: pure sulphate of quinine is completely consumed; whereas, the mineral substances present remain behind as a residue.
c. In presence of salicine, the salt acquires a deep red color, when treated with concentrated sulphuric acid.
d. Stearic acid remains undissolved upon treating sulphate of quinine with acidulated water.
e. To detect sugar and mannite, the sample is dissolved in acidulated water, and an excess of hydrate of baryta added: a precipitate, consisting of quinine and sulphate of baryta, is
f. Sulphate of quinine invariably contains 2 or 3 per cent. of cinchonine, originating, not from a fraudulent admixture, but from an incomplete purification of the salt. One of the best methods for detecting the respective quantities of quinine and cinchonine, present in a sample of the sulphate, is the following: Several grammes of ammonia and ether (which has previously been washed with water) are added to one or two grammes of the salt under examination, the mixture thoroughly agitated, and then allowed to remain at rest. The supernatant etherial solution contains all of the quinine; the cinchonine, which is almost completely insoluble, both in water and ether, remaining suspended between the layers of the two fluids. The ether is next removed by means of a stop-cock funnel, evaporated to dryness, and the weight of the residue obtained determined. The operation is then repeated, the ether being replaced by chloroform in which both quinine and cinchonine are soluble. The residue, formed by the evaporation of the second solution, will be heavier than the first residue: the difference between the two weighings gives the weight of the cinchonine present.
g. The detection of the presence of sulphate of quinidine is based upon the difference in the solubilities of the oxalates of quinine and quinidine. Oxalate of quinidine is sufficiently soluble in cold water not to be precipitated by double decomposition when solutions of oxalate of ammonia and sul
The suspected salt is dissolved in water, a slight excess of oxalate of ammonia added, and the precipitate formed separated by filtration. If the salt be pure, the filtrate is scarcely rendered turbid by the addition of ammonia; when, however, sulphate of quinidine is present, it will be entirely contained in the filtrate, in which ammonia will produce an abundant precipitate.
EXAMINATION OF BLOOD STAINS.
This branch of legal chemistry formerly gave but very unreliable results. It is scarcely ten years since the reactions that are now regarded as only secondary and confirmative in their character, and far from conclusive, were the only ones in use: these are the tests based upon the presence of iron and albumen in the blood. Since then, great progress has been made in the methods employed. It must not be understood, however, that the question under consideration always admits of an easy and decisive solution: the stains are sometimes too greatly altered to be identified; but in cases where the distinctive reactions of blood can be produced, the real nature of the stains under examination can, at present, be determined with certainty.
The tests more recently introduced consist in the production of small characteristic crystals, termed haemin crystals, and in the use of the spectroscope. Crystals of haemin (first discovered by Teichman) are formed when dry blood is dissolved in concentrated acetic acid, and the solution evaporated to dryness: they are of a brownish-red color. BrÜcke first suggested an analytical method, based upon this property of
The former possess a reddish-brown, the latter a lighter color.
The various methods now employed to produce haemin crystals were proposed by Hoppe-Seyler, by BrÜcke and by Erdman. Whichever process is used, the suspected stains are at first carefully separated from the material upon which they are deposited. If they are present on linen, or other fabrics, the stained portions, which always remain somewhat stiff, are cut off: they will present a reddish-brown color, in case the cloth is not dyed: if the stains are on wood, they are removed by means of a sharp knife; if on stone or iron, they are detached by scraping.
In case Hoppe-Seyler's method is used, the stains, separated as directed above, are macerated with a little cold water (warm water would coagulate the albumen present, and consequently
In order to remedy this difficulty BrÜcke operates directly upon the stained woven or ligneous fibre, or the matter removed from the stone or iron: The materials are boiled in a test-tube with glacial acetic acid, the fluid decanted or filtered, a trace of common salt added, and the liquid then evaporated on a watch-glass at a temperature between 40 and 80°. If the stains really originated from blood, haemin crystals will now be easily perceptible upon examining the residue obtained under the microscope.
The stained fabric, the matter removed from the stone or iron, or the residue left by the solution with which the stains have been treated, is placed on the glass, a trace of chloride
Should the above test fail to present distinctive indications at first, one or two fresh drops of acetic acid are introduced between the plates, and the examination is repeated. The result is not to be regarded as negative, until several trials have proved fruitless, as the stained portions are but slowly soluble, and crystallization may have been prevented by the too rapid evaporation of the acetic solution.
Haemin crystals, once seen, can hardly be confounded with other substances; still, it is well to identify them by confirming their insolubility in water, alcohol, and cold acetic acid, as well as their instantaneous solubility in soda lye.
The addition of common salt is ordinarily superfluous, as it is normally contained in the blood; but it is possible, if the stains were washed with warm water, that, in addition to the coagulation of the albumen, the solution of the salt may have taken place, in which case crystals will fail to form. The addition of salt is to remedy this possible contingency; albeit, the delicacy of the test is not affected, even if crystals of chlo
The indications furnished by means of the spectroscope are less reliable than those given by the production of haemin crystals; moreover, the spectroscopic examination requires favorable weather for its execution. Still, the test should be employed in all possible instances. The course pursued is the following:
The aqueous fluid, with which the stains have been treated, is placed in a watch glass, and evaporated in vacuo over sulphuric acid; the last remaining portion of the fluid being united in the bottom of the glass by causing it to collect in a single drop. When the evaporation of fluid is completed, the watch-glass is placed before the narrowed slit of a spectroscope, and a ray of diffused light (or better, light reflected from a heliostat) made to pass through the part of the glass containing the residue. If the stains originate from blood, the absorption lines of haemoglobin, consisting of two large dark bands, to the right of the sodium line (Frauenhofer's line D), will be observed in the spectrum. In case both of the above tests fail to give positive results, it is almost certain that the stains examined were not caused by blood. If, on the contrary, the reactions were produced, scarcely any doubt exists as to the presence of blood. Under these circumstances it is advisable to confirm the results by means of the tests that have been previously spoken of as being formerly exclusively employed; these are the following:
a. 1/2 to 1 c.c. of ozonized oil of turpentine, i.e. turpentine which has been exposed to the air sufficiently long to acquire the property of decolorizing water that is slightly tinted with indigo—is introduced in a test-tube, and an equal volume of
If upon adding some of the substance under examination to the above mixture a clear blue coloration ensues, and the insoluble matter thrown down possesses a deep blue color, the presence of coloring matter of the blood is indicated. The mixture also imparts a blue color to moistened spots from which the blood stains have been as completely extracted as possible. Unfortunately sulphate of iron gives the same reaction.[X]
b. Upon heating the fluid obtained by treating the stains with cold water in a test-tube, its brown or reddish color disappears, and greyish-white flakes of coagulated albumen are thrown down. The precipitate acquires a brick-red color, when treated with an acid solution of nitrate of mercury containing nitrous acid. The albumen is also coagulated by the addition of nitric acid: it assumes a more or less yellow color, if heated with a slight excess of the acid. Chlorine-water, especially upon heating, likewise precipitates albumen in the form of white flakes.
c. If the fluid is acidulated with a few drops of acetic acid, and a drop of ferrocyanide of potassium added, a white precipitate, or, at least, turbidity is produced.
d. The flakes of albumen, separated by heating, dissolve in caustic alkalies to a solution, from which they are re-precipitated by nitric acid, or chlorine water.
e. Upon treating blood stains with chlorine-water, a solution which contains chloride of iron, and acquires a red coloration by the addition of sulphocyanide of potassium, is formed.
f. Should the stains have failed to be affected by cold water (which, as has already been remarked, is the case when they have been previously washed with hot water), they are treated with weak soda lye. Nitric acid, hydrochloric acid, and chlorine water will produce in the solution so obtained a white precipitate, which exhibits the general properties of albumen previously described. In case the stains are deposited upon linen, it is necessary to replace the soda by ammonia, in order to avoid dissolving the fabric.
g. Solutions of the alkalies, which dissolve the albumen, leave the coloring matters intact, and consequently do not decolorize the fabric. If the latter is afterwards subjected to the action of hydrochloric acid, the coloring matter is dissolved, forming a solution that leaves upon evaporation to dryness a residue containing iron, which gives a blue coloration with ferrocyanide of potassium, and a red coloration with sulphocyanide of potassium.
h. The coloring matter of blood dissolves in boiling alcohol, to which sulphuric acid has been added, to a brown dichroic fluid (appearing green by transmitted light, and red by reflected light). A mixture of rust and blood exhibits the same phenomenon.
i. If substances containing blood are heated in a dry tube, an odor resembling that of burnt horn is emitted. In case the stained fabric is a substance that would produce this odor, (such as wool, silk, or hair), the test naturally loses all value.
j. If the fluid obtained by treating the stains either with water or alkali is evaporated with a little carbonate of potassa, and the residue heated, at first at 100°, then to redness, in a glass tube to which a fresh quantity of carbonate of potassa has been added, cyanide of potassium is formed. When cold, the tube is cut above the part containing the fused mixture,
If the stained cloth is non-nitrogenous (per ex.: hemp, linen, or cotton), instead of treating it with water, it may be heated until pulverulent, mixed with carbonate of potassa, the mixture calcined, and the operation then completed as just described. This test having given affirmative results, the operations should be repeated with an unstained portion of the cloth, to remove all doubt that the indications obtained do not really originate from the fabric.
In the present state of science, it is impossible to discriminate chemically between human and animal blood. M. Barruel, it is true, is able, not only to accomplish this, but also to distinguish the blood of the various species of animals by its odor! But this test has a somewhat hypothetical value for scientific purposes. In regard to the crystals of haemin, they do not present sufficient difference to allow the blood of different animals to be distinguished. We have not yet treated of the globules. It often occurs that these minute organs are so altered as to be no longer recognized in the microscopic examination; when, however, the stains are tolerably recent, they may be detected by examining the moistened stained cloth, directly under the microscope: a discrimination between animal and human blood is then possible: corpuscules of human blood possess the greater size: those of the sheep, for instance, have only one-half the diameter of the former. It is, however, but seldom that this distinction can be made use of.[Y]
EXAMINATION OF SPERMATIC STAINS.
In cases where attempt at violence, rape or pederasty is suspected, the expert may be required to determine the nature of stains found on clothing, sheets, etc. The fact that the stains were produced by semen, may often be regarded, per se, as criminating evidence. This class of investigation possesses, therefore, considerable importance.
External appearance of the stains.—Dry spermatic stains are thin, and exhibit a greyish or, occasionally, a citron-yellow color, if present on white cloth. In case the fabric is colored, they appear whitish and, if on linen, present a glossy aspect. They are translucid, when observed by transmitted light. If the fabric, upon which the stains are deposited, is of a heavy texture, they are visible only on one side: under all circumstances, their circumference is irregular and undulated. These indications, however, are not conclusive, but vary according to whether the stains were produced by the thick semen of a vigorous man, or the aqueous seminal fluid of an aged and diseased person, or by semen more or less mixed with the prostatic fluid. Upon moistening spermatic stains, the distinctive stale odor of fresh semen is sometimes emitted, but this characteristic is usually obscured by the presence of foreign substances.
Semen stains are soluble in water, forming a gummy fluid, in which chlorine, alcohol, bichloride of mercury, acetate and subacetate of lead produce a white precipitate, but which fails to be coagulated by heating. Plumbate of potassa does not impart a fawn-color to these stains, at a temperature above 20°, as is the case with those produced by albuminous substances.
Persulphate of iron imparts to spermatic stains a pale yellow color,
Sulphate of copper, a bluish grey color,
Cupro-potassic tartrate, a bluish grey color,
Nitrate of silver, a pale grey color,
Nitric acid, a pale yellow color.
The above reactions, separate or united, are insufficient; they are not very delicate, and are likewise produced by stains originating from the other varieties of mucus: the indications furnished by a microscopic examination of the stains are alone conclusive.
Microscopic examination.—Semen contains as its principal and fecundating constituent, peculiar vibratory filaments, (spermatozoa), held suspended in a viscous fluid. These filaments, when preserved in a warm and moist place, retain their activity for a considerable time: it is even possible that they may exhibit vitality in the organs, into which they have been voluntarily or forcibly ejaculated, for ten, or even twenty-four hours. When exposed to cold air, the spermatozoa quickly expire; still, they preserve their form for some time, and, as this is very characteristic, it is then easy to identify them; moreover, since they originate exclusively in the testicles, their detection may be considered as certain evidence of the presence of semen. In stains produced by aged persons, and by persons enfeebled by excesses, the spermatozoa fail to be presented; in case they are discovered, this fact evidently does not affect the certainty of the spermatic origin of the stains. The contrary conclusion is never absolutely certain: still, if the use of the microscope fails to establish the presence of spermatozoa, it is almost certain that the stains were not produced by semen.
Of the various methods for obtaining from the stains a
A strip, 1 c.c. in size (comprising the entire stain, if this be small, containing its inner portion, if it be large), is cut from the fabric under examination, care being taken that the two extremities of the sample extend beyond the stained portion.
One end of the cloth is then immersed in a capsule, or watch-glass, containing pure water: the stains become moistened by capillary attraction, and, in a space of time varying from twenty minutes to two hours, acquire the appearance of fresh semen. As soon as the stained portion becomes swollen and softened, the surface of the cloth is gently scraped with a spatula, and the substance removed placed on the slide of the microscope. The particles are next slightly detached, a drop of water added, if necessary, and the whole covered with a small plate of very thin glass. The preparation is then examined by a microscope, having a magnifying power of from 500 to 600 diameters. In this way, the presence of either entire or broken spermatozoa is readily detected. Their existence is rendered still more apparent, if the mucus present is dissolved by adding a drop of acetic acid to the preparation.
Entire spermatozoa consist of long slender filaments, having a length of 0.04041 to 0.04512 millimetre; the anterior extremity presents an oval enlargement, either round or pyriform, exhibiting a double outline, when magnified to 500 diameters. This enlarged end is termed the "head;" the entire remaining portion being regarded as the "tail." In case the spermatozoa are broken, they are severed either near the head or in the middle of the tail, and a mass of detached fragments will be observed in the microscopic examination. The spermatozoa are not the only corpuscules revealed by the microscope; other substances, entirely different in character, are often observed.
a. Oily globules.
b. Leucocytes, or spherical and finely granulous globules of mucus.
c. Corpuscules, originating from the seminal vesicles, termed sympexions. These are rounded or ovoid, possess an irregular outline, and are usually mixed with the spermatozoa and globules of mucus.
d. Crystals of phosphate of magnesia, varying greatly in size; the largest are from 0.mm.001 to 0.mm.002 in length. The crystals formed upon cooling the semen, present the form of an oblique prism, with a rhomboidal base. Occasionally they are elongated and flattened; they then assume the form of a rhomboid.
e. Epithelial cells; originating from the mucous follicles of the urethra.
f. Irregular grains of dust; soluble in acetic and hydrochloric acids, with gaseous evolution.
g. Brownish-red grains of rust; only slightly soluble in acetic acid, but easily soluble in hydrochloric acid.
h. Filaments of the strained fabric; detected by their texture, and general appearance.
i. Grains of starch, in case the cloth has been stiffened. These are almost invariably swollen, and are frequently broken and deformed.
If the examination is to be secretly executed, and the cloth cannot well be cut, it is rolled in a cone, in such a way that the external side contains the stained portion. The lower extremity of the cone (which should be free from stains) is dipped in a watch-glass containing water, so as to avoid directly wetting the stains. The cone soon becomes moistened
The examination of spermatic stains consists, then, in moistening the stains with water, separating them as completely as possible from the stained cloth, and determining the presence of the spermatozoa by means of the microscope.
All other tests are valueless; even their execution for confirmatory purposes is not advisable; inasmuch as they fail to possess a distinctive character, and the reagents employed in their production may destroy the fabric, and thus prevent the formation of the only conclusive reaction—the detection of the spermatozoa.
In case the stains are deposited upon a woman's chemise, they are usually present on both the front and back portions, and are sometimes to be found on the sleeves. When a man's shirt is under examination, especial attention should be given to the anterior portions. The pantaloons are also often stained; usually in the interior, but sometimes also on the exterior, just above the thighs. In reporting the decision to the court, as to the nature of the stains, their precise position should invariably be stated, as, by this means, the circumstances attending the commission of the crime may be, at least partially, elucidated.
THE END.