PATENTS.

In Chapter VII. we have described a few of the many artificial bates which have been proposed, and for which in many cases patents have been taken out. It would be impossible within the limits of a single chapter to give an adequate account of all these patents, and therefore it is not proposed to deal with those which are merely deliming processes, but solely those in which the use of bacteria and enzymes is directly applied. We mention, however, one or two of the more interesting deliming patents.143

Amend, Otto Paul, New York (U.S. Pat. 763,347, 1904; Eng. Pat. 18,514 and 18,514A, 1904).—Improved Process for Bating and Puering Skins, and Improvements relating to the Bating, De-acidifying and Oxidizing of Hides and Skins.

The skins are treated with a solution of an ammoniacal salt, small quantities of an acid such as hydrochloric acid being added at intervals, so as to reform the salts. Pickled skins are de-acidified and oxidized by treatment in a neutral or slightly alkaline solution of a nitrite of an alkali or alkaline earth such as sodium nitrite.

Nowak, O.H., Chicago (French Pat. 360,854, 1905; Eng. Pat. 26,771, 1905).—Substance for Treating Hides and Process for Making same. This is the “dermiforma” described in Chapter VII. Although bacterial action is used to prepare the bate, the essential action is an acid one, and, as we have said, resembles the drench.

Norris, W.M., New Jersey (U.S. Pat. 840,794, 1907; Eng. Pat. 29,661, 1906).—Improved Process of Treating Hides and Skins. In this process the skins are subjected to treatment with a dilute solution of hyposulphite of soda, which is said to “set” the gelatinous fibres of the skin. The deliming is completed with hydrochloric acid in the presence of salt.

Boehringer Sohn, C.H. (Eng. Pat. 3,140, 1911) Proposes to use in place of the free organic acid, in this case lactic, the sodium salt, and then to add slowly the amount of hydrochloric or sulphuric acid requisite for deliming. The mineral acid combines with the sodium salt, liberating an equivalent amount of the weaker organic acid, which then acts upon the lime in the skins. For deliming 100 kilos. of pelt, 0·25 kilo. of sodium lactate (50 per cent.) and 0·56 kilo. hydrochloric acid (20° BÉ.) are used.

The advantage of the method is that a considerable saving is effected in comparison to the quantity of the free organic acid which would be required. In the above example 1 kilo. of lactic acid (43 per cent.) would be required to neutralize a corresponding amount of lime.

In addition to these deliming processes, there are a number of bates in which various nutritive media are allowed to ferment naturally, without the addition of any specific bacteria. Among these may be mentioned:—

Dr. NÖrdlinger’s Bate, in which a paste of potatoes is allowed to ferment at 30°–37°C. for several days; it is then dried at 40°–50°C., and used in the same way as dog dung.

H.E. Simons’, Phosphorbutyralin, consists of the beetroot residues in sugar manufacture which have undergone an acid fermentation, and contain butyrates and phosphates of ammonia.

Oakes (US. Pat. 798,070, 1905; Eng. Pat. 24,488, 1905).—In this patent an albuminous body, such as casein is allowed to putrefy, at a temperature of 100°F., for several days; an equal weight of flowers of sulphur is then added, and the mixture used as a bate or puer. The sulphur is said to play an essential part in the bate.

A similar process, by the same author (U.S. Pat. 798,293), is described by Dr. Allen Rogers144 in which 5 per cent. of glucose syrup and 10 per cent. of sulphur, computed on the weight of the skins, is fermented with yeast for twenty-four hours, after which it is used as a bate. From a chemical point of view, it is difficult to express the reactions taking place.

When the bath is first prepared, it is neutral in reaction, but, after standing, gradually assumes a slight acid reaction. On introducing the skins, it becomes alkaline, owing to diffusion of the lime. After a short time, it becomes neutral again, and remains thus until the skins are in a perfect condition, when a slight acid reaction is observed. These changes are caused by the fermentation of the glucose, carbon dioxide and alcohol being generated. Owing to the presence of sulphur, a quantity of hydrogen sulphide is produced, which, in its nascent condition, combines with the alcohol to form mercaptans, which in their turn are slowly oxidized to thioacids. These mercaptans and thioacids, being of weak acid character, act in conjunction with any excess of hydrogen sulphide upon the lime, converting it into soluble compounds, which are readily removed by diffusion.

Lederer, L. (French Pat. No. 404,926 of 1909).—Method of Preparing a Substitute for Animal Excrement (dog dung) in Puering Skins for GlacÉ Leather. In this process a mixture of 10 parts finely powdered bone meal, and 1 part of crushed lupin seeds or beans is formed into a paste with water and allowed to undergo spontaneous fermentation from 3–4 weeks. The mixture is said to form a perfect culture medium for the micro-organisms indispensable in bating. The removal of the lime is facilitated by the addition of 2 per cent. of fat, 0·75 per cent. sodium polysulphide and 1 1/2 per cent. common salt reckoned on the weight of the bone meal.

In this patent the researches of Wood, Andreasch and Eitner are referred to, and also Benker’s process of bating with Peruvian guano to which soda has been added.

Turney, Sir J. and Wood, J.T.—Coming now to bacterial and enzymatic bates, the author in conjunction with Sir John Turney applied for a patent for a new and improved method of bating skins (No. 25,894, 1896), in which cultures of suitable bacteria were to be used in place of infusions of dog or pigeon dung. It was found however that this patent had been anticipated by the patent 21,720 of 1895, of Dr. Popp and Dr. Becker of Frankfort o/M, and the application was therefore not proceeded with. As has been related in Chapter VII. the late Franz Kathreiner, who knew of the work which was being done both by Dr. H. Becker and the author, made us personally acquainted, and most of our later work was done in conjunction. Like many other new ideas, it was arrived at quite independently by Dr. H. Becker and the author. (See Report of Third Conference of I.A.L.T.C., Copenhagen, 1899, Wiss. Techn. Beilage des Ledermarkt, 1899–1900, p.8.)

We shall therefore give the original patents in full, and afterwards the translation of Dr. Otto RÖhms’ patent, and the recent patent of Dr. Eberle, as these cover the whole ground of the bacterial and enzymatic bates up to the present time.

Dr. Popp and Dr. Becker’s English Patent (No. 21,720, 1895). Improvements in Lyes or Liquors for Preparing Hides for Tanning. An important role in the process of manufacture of many kinds of leather is played by the dung liquor or lye, which in particular for calf skins and skivers constitutes one of the necessary preparatory operations for the subsequent actual tanning process, and which has for its purpose to bring the skins or hides, which have been previously swelled by the liming process, into a condition which allows the easy and thorough removal of the lime and lime soap as well as the remaining hairs by the subsequent mechanical treatment, and to obtain a uniform shrinking of the swelled hides.

The process hitherto employed consists in treating the hides or skins for some time (such as for 4 or 5 hours) in a vat provided with a reel, and containing a lye or brine formed of solutions of dog or pigeon or poultry dung.

Generally speaking, the dog dung acts best in some cases, and pigeon or poultry dung in other cases, but no satisfactory and sound explanation has as yet been given as to the nature of the action.

My correspondents have in the first place ascertained that the action of these lyes or brines is the result of bacteriological processes, especially of the products created by the action of certain bacteria, and is certainly not, as it has hitherto been generally assumed, the result of the action of phosphoric acid or other acids.

The examination of the dog, pigeon and poultry dung in bacteriological respect, and of the industrial applicability of all the different results obtained, shows in the first instance that, even after removal of all other ingredients, which, according to the hitherto ruling views, enter into reaction, the result of the treatment remains the same as it had been before the removal. The continued research led to the second result that a great number of micro-organisms play a role in the lye, partially an advantageous, and partially a detrimental one.

Generally speaking, the non-peptonizing bacteria act advantageously, while the peptonizing ones generally have a detrimental effect. In connexion herewith two methods of utilizing these discoveries have been found.

One can either, according to the methods of bacteriology (plate process), remove all the detrimental or even the less useful bacteria, and effect the treatment of the hide or skins by applying a pure culture of one or at least a mixture of the different most effective bacteria; or one can, without employing such a refined process, but still utilizing the said discoveries, apply the dog dung, and in particular the white descriptions which are most effective, or, for certain kinds of leather, the pigeon or poultry dung, subjecting the said dungs to a certain treatment, which, by the use of a suitable cultivating bed, will develop the useful bacteria, while on the other hand, the increase of detrimental bacteria may be prevented or retarded by the addition of materials hindering the development of the latter.

In every case the employment of the process secures greater rapidity of execution, and more reliable and better results than the process heretofore applied.

The leathers obtained are tough and yet softer, and in any case any discolouring, such as is often unavoidable with dog dung, is avoided.

An advantage not to be underrated with the use of germ cultures, is that liquors or cakes having a definite percentage of really effective substance can be prepared, whereas it was heretofore necessary to proceed by way of trials, the result being subject to great uncertainty.

In addition, the dung liquors are subject to changes overnight under the influence of atmospheric changes (thunder-storms) in a most unaccountable manner, owing, as has now been discovered by my correspondents, to the growth of detrimental bacteria which are mixed with the effective ones, and which gain the upper hand over the latter under the change of atmospheric conditions.

The features of the newly discovered useful bacteria are fully described in the following, and experiments have shown that the particular kinds designed with 3, 7 and 12 in the table of bacteria, set forth in the Specification to German Patent No. 86,335 and hereinafter fully described, are those which are of value for the purpose in question; in particular No. 12 is the most effective, and 3 the least effective of these three descriptions.

All three are bacteria to be found in the dog dung, and bacteria No. 3 consists of very small rods rounded at the ends and are exceedingly mobile, while bacteria No. 7, which are similar to the hay bacillus, are slowly-moving rods, and bacteria No. 12 are medium-sized rods having rapid motion.

The prick-culture gives with bacteria No. 3 a very good growth in the depth; from the inoculating prick extend laterally many arms into the gelatin. At the ends of the arms are formed small knots. On the surface is formed a thin white covering. The gelatin is not liquefied.

On gelatin plates, the deep-seated colonies consist of pale yellow round disks, which gradually penetrate to the surface, and there they form circular disks which show at the centre larger spots. On inclined agar-agar there is formed a white superstratum.

With bacteria No. 7, the gelatin is strongly liquefied in the prick-culture. On the surface of the zone of liquefaction there is formed a white skin.

Along the liquefied prick are formed radiations into the solid gelatin. On gelatin plates there are formed rapidly liquefying colonies forming at top a white skin, agar-agar gives a white unequal thin superstratum with branchings.

Bacteria No. 12 grow with prick-culture equally well along the prick; the gelatin is not liquefied. On the surface there is formed a thin shining covering.

On gelatin plates, the deep lying colonies consist of pale yellow circular disks.

Many colonies have tails similar to the surface colonies of the Proteus. During the growth of this bacterium on gelatin plates a strong putrid smell is developed.

On agar-agar this bacterium forms a strong white shining superstratum.

These bacteria grow easily in any decoction of meat, and the flesh particles from the flesh sides of the hides, which otherwise form a waste product of little or no value, may be advantageously employed for this purpose; bran, and other materials known to offer good culture-beds, may be employed instead.

For this purpose a vessel provided with a cover is charged with equal parts of waste flesh, such as is obtained in the tannery, and water, and this is boiled for about half an hour by the direct introduction of steam, after which concentrated carbonate of soda solution is introduced until the reaction is slightly alkaline, after which the decoction is cooled down. As soon as the temperature has sunk to about 35°C. there is added the pure culture obtained by the gelatin plate process (with dilution), described in the works on bacteriology of Koch, Fraenkel, Hueppe and others, and also by the further treatment corresponding to the characteristic peculiarities of the bacteria, and the whole is allowed to stand covered up for a period of from twelve hours to five days, depending on the time of year and the temperature.

The hides or skins are then dipped into the concentrated decoction for a short time, according to the state of development of the bacteria; or the decoction can be diluted and the hides be then immersed therein for a greater length of time.

The further treatment is then carried out in exactly the same way as though the hides or skins had been treated in dog-dung lye, with the exception that the duration is shorter.

In case the pure culture of the bacteria is to be dispensed with, and it is only desired to obtain an advantage over the existing methods in so far as to obtain, on the one hand an artificial increase of the ooze medium viz. the number of useful bacteria and their products existing in the dog dung, by providing a suitable culture bed, and on the other hand to be in a position to limit oneself to the best initial material, the process can be carried out by starting with a practically proved dog dung, therefore in particular the white kinds, and the bacteria are caused to propagate in a decoction such as above described. Afterwards it is advantageous to effect the killing of the detrimental bacteria by a small addition of acid, such as 0·5 per cent. of dilute sulphuric acid or equivalent materials, as in this case the useful bacteria are also the most enduring.

The more useful bacteria show, in particular in the presence of alkalis, the same behaviour.

For example, the more useful bacteria arrive at development equally with the detrimental ones, if to the described culture bed be added 0·5 per cent. of carbonate of soda, while the useful bacteria preponderate to a considerable extent, and the detrimental ones are practically unimportant, if the additions of carbonate of soda be raised to about one per cent.

The pure cultures of the bacteria may be preserved in a suitable liquid or solid material, and brought on the market in a suitable packing.

In order to obtain a product which shall both be durable, and capable of being delivered in definite doses, sterilized bran, flour, etc., can be inoculated with definite quantities of the pure cultures, and the percentage of water be reduced, by drying, pressing, etc., to under a certain percentage (10 to 12 per cent.) which will not allow of, or will retard the evolution of germs.

The bacteria may also, after having been properly developed, especially after having created a sufficient quantity of their products, be killed, for instance by heating, and the resulting stuff be brought on the market in liquid or solid form, as an effectual lye or brine, it having been found that the liquids containing the said bacteria do not lose their effect if they are sterilized and the bacteria thereby killed, provided that a sufficient number of bacteria has been produced.

Claim.—1. The process for the production of a lye for treating hides or skins preparatory to tanning, consisting in the propagation of the bacteria of dung, in particular dog and bird dung, by means of suitable culture beds substantially as described.

2. As a new article of manufacture a lye containing a pure culture of one or more of the described bacteria.

3. In the process of producing a lye referred to in the first claim, the elimination of the detrimental agents substantially as described.

4. In the process referred to in the first claim, the addition of acids or alkalis for the purpose set forth and substantially as described.

5. The process for the production of a lye for treating hides, consisting in the separation from the dung of the bacteria herein designated as 3, 7 and 12, producing pure cultures thereof, and introducing the same into a decoction preferably freed by boiling from other bacteria and containing a suitable culture bed, substantially as described.

6. A process for the production of cakes, for the treatment of hides, consisting in the inoculation of sterilized bran, flour, etc., with cultures having a definite percentage of bacteria and the removal of the proportion of water that is necessary for the development of the bacteria, substantially as described.

7. As a new article of manufacture sterilized cakes, containing a certain quantity of the described bacteria, substantially as described.

8. As a new article of manufacture the solid or liquid material containing the products of the decomposition, as generated by the pure cultures of the said bacteria, whether such material does or does not also contain the said bacteria, either in the active condition or killed by sterilization, substantially as described.

Wood’s English Patent (12,549, 1898).—Improvements in and relating to the means used for the Bating of Hides and Skins. This invention has reference to improvements in and relating to the means, liquid or bate, used for the bating or puering of hides and skins previous to the process of tanning the same.

At the present time skins are usually bated by means of a liquid or bate prepared from dog or pigeon dung, and although the bating action or actions have not hitherto been thoroughly understood, it is a well known fact that fermentations going on in the dung play an essential part. It was also pointed out in 1885 by H.R. Procter, in his “Text Book on Tanning,” that the action of the bate was in a great measure due to bacteria. It is also a known fact to practical tanners that a dung bate, properly applied, produces the best quality of leather.

Owing, however, to the varying composition of the dung used, the bate made therefrom possesses varying properties, its bating action is uncertain, its properties are readily affected by atmospheric influences, and the skins treated are liable to putrefaction.

As a substitute for dung bate, it has been proposed, as set forth in the Specification of Patent No. 21,720, A.D. 1895, to use a bate made from a pure culture of bacteria. Such bate, however, does not possess all the essential properties of a dung bate; and although bacterial action is necessary, such action alone is not sufficient, as was pointed out by the present inventor in 1894 in the “Journal of the Society of Chemical Industry.”

The present inventor has now discovered that the bating action of a dung bate is due to the combined action of enzymes or unorganized ferments, and to certain amine compounds in the dung. These compounds consist of amines (i.e. ammonia in which one or more atoms of hydrogen has or have been replaced by alcohol radicles), in combination with lactic, acetic and other organic acids contained in the dung, the acids named being the principal ones.

The present inventor has also discovered that the bating action of the enzymes alone, or the action of the chemical compounds alone, are inefficient, and that the enzymes exert their bating action in the presence of the chemical compounds, while these latter in addition have an independent action.

The object of this invention is the production, according to scientific methods, of a bate having similar properties to those of a dung bate, such properties in the improved bate being defined and definite, but capable of being modified according to the requirements of the skins to be bated and the leather to be produced.

According to this invention, the liquid or bate is made by producing by fermentation an enzyme or enzymes of the same character as the enzymes contained in dog dung or produced from bacteria obtained from dung, and to the liquid thus obtained there is added an organic acid and an alkali.

The inventor has discovered that for an efficient bate a pure culture of bacteria is insufficient, and that no single organism hitherto isolated will give results equal to dung. He has also discovered that the production of these enzymes depends more upon the composition of the nutrient medium in which the bacteria are cultivated than upon the kind of bacteria, although these latter must be capable of producing the required enzymes, the production of which appears to be due to a symbiotic growth of bacteria, at present little understood.

It is desirable that the nutrient medium should be without sugars or starchy matters, and, although the composition of the nutrient medium may be varied, good results can be obtained according to ordinary bacteriological methods by using a medium composed of—

This medium is maintained at a temperature of about 37°C. (the most favourable temperature for the fermentation) until the required bacterial action is completed, the time necessary being about seven days, and to each litre of the liquid thus obtained there are added from 2 to 6grs. of lactic acid. Acetic or other similar organic acid may be used instead of the lactic acid, but sulphuric or mineral acids must not be used. The acid liquid is afterwards neutralized by ammonia, which is added when the bate is to be used, and there are then formed certain chemical compounds similar to those found in a dung bate.

The addition of the acid to the nutrient medium will immediately stop the growth of bacteria, but the acid is not added for that particular reason, but for the particular purpose set forth.

Instead of the enzymes obtained from the bacteria of dung, other enzymes of a similar character may be used, such as the enzymes obtained from the bacteria found on skins during the sweating process.

For bating skins in a practical manner with the improved bate herein set forth, the method of using the same is preferably varied according to the skins to be treated and the kind of leather it is required to produce. Thus for kid skins, skivers and other skins for which dog dung has hitherto been used, the skins, after the liming process, are first well washed in water in the usual way to remove the bulk of the lime. The skins are then placed in a wheel or paddle with the bate prepared as before described, with the acid exactly neutralized by the ammonia or so nearly neutralized that the alkaline action of the skins will complete the neutralization, all skins being alkaline when introduced into the bate.

The bate is diluted according to the amount of liming the skins have undergone, and when in the paddle or wheel the skins and bate are maintained at a temperature of about 37°C., and the skins paddled until they have “fallen” considerably. The skins are then removed from the wheel or paddle and scudded preferably on the “grain” side, after which they are returned to the wheel or paddle and the paddling continued until the bating action is completed, this being judged in the usual way by a practical tanner according to the feel of the skins. The strength of the bate after the scudding process may be varied if found desirable.

After the bating process is completed the skins are treated in the usual manner.

When the improved bate is to be used for light hides and similar skins which have hitherto been treated with pigeon dung, the skins, after the liming process, are washed in the usual manner, heated to a temperature of about 37°C., and placed in a wheel or paddle containing by preference the improved bate in an acid condition, that is before the ammonia has been added, the bate being previously diluted according to the amounts of liming the skins have undergone. The skins are then paddled until the tanner, by the feel, judges that the whole of the lime has been removed. The acid bate is then neutralized by ammonia, with or without removing the skins, and the paddling is continued until the bating process is completed, this being judged of by the feel of the skins.

The bated skins are then scudded, washed, and treated in the usual manner.

The strength of the bate, into which the skins are placed for both methods, is varied according to the amount of liming the skins have undergone; that is to say, for “high” limed skins, a stronger bate is required than for skins which have been subjected to a moderate liming.

Claim.—1. A bate having the essential properties of a natural dung bate, but prepared according to scientific methods from the means and in the manner substantially as set forth in the accompanying specification.

2. The bate described and set forth in the accompanying specification.

Wood’s American Patent (638,828, Dec. 12, 1899) Bate.—This invention has reference to improvements in and relating to the means, liquid, or bate, used for the bating or puering of skins previous to the process of tanning the same.

At the present time, skins are usually bated by means of a liquid or bate prepared from dog or pigeon dung; and, although the bating action or actions have not hitherto been thoroughly understood, it is a well-known fact that fermentations which the dung undergoes play an essential part. It was also pointed out, by H.E. Procter in 1885, in his “Text Book of Tanning,” that the action of the bate was in a great measure due to bacteria. It is also a known fact to practical tanners that a dung bate properly applied produces the finest and most supple leather. Owing, however, to the varying compositions of the dung used, the bate made therefrom possesses varying properties: its bating action is uncertain, its properties are readily affected by atmospheric influences, and the skins treated are liable to putrefaction.

As a substitute for a dung bate, it has been proposed, as set forth in the specification of the British Patent No. 21,720, A.D. 1895, and the specification of the German Patent No. 86,335, Class 28, to use a bate made from a pure culture of bacteria. Such bate, however, does not possess all the essential properties of a dung bate, and, although bacterial action is necessary, such action alone is not sufficient, as was pointed out by me in 1894 in the “Journal of the Society of Chemical Industry.”

I have now discovered that the bating action of a dung bate is due to the combined action of enzymes, or unorganized ferments, and certain chemical compounds, which compounds consist principally of amines—i.e. ammonia in which one or more atoms of hydrogen has or have been replaced by alcohol radicles—in combination with organic acids usually found in dung, and of the compounds so formed the lactates and acetates are the most important. I have also discovered that the bating action of the enzymes alone, or the action of the above-referred-to chemical compounds alone, is inefficient, and that the enzymes exert their bating action in the presence of the chemical compounds, while these latter, in addition, have an independent action on the limes in the skins, and on the skin fibre.

The object of this invention is the production, according to scientific methods, of a bate having similar properties to those of a dung bate, such properties in the improved bate being modified according to the requirements of the skins to be bated and the leather to be produced.

According to this invention, the liquid or bate is made by producing by fermentation, an enzyme or enzymes of the same character as the enzymes contained in dog dung, or produced from bacteria contained in the dung, and to the liquid thus obtained there is added an organic acid and an alkali.

I have discovered that for an efficient bate a pure culture or single species of bacteria is insufficient, and that no single organism hitherto isolated will give results equal to dung. I have also discovered that the production of enzymes of the character above referred to, depends more upon the composition of the nutrient medium in which the bacteria are cultivated, than upon the kind of bacteria, although these latter must be capable of producing the required enzymes, the production of which appears to be due to a symbiotic growth of bacteria at present little understood. The bacteria used for the purpose of this invention may be the bacteria found in dog dung, or the bacteria obtained from the roots of the hairs of skins during the sweating process, these latter being used, by preference, on account of the ease with which they are obtained, compared with the difficulty of isolating from the dog dung the particular mixture of species most desirable, there being so many undesirable species present. Of the bacteria found on the roots of the hair during the sweating process, and hereinafter referred to as “sweating” bacteria, I have found that two species predominate, and, so far as I am aware, these have not been previously isolated. The principal organism, which I call “bacillus d,” in continuation of a series of previous investigations described in the “Journal of the Society of Chemical Industry,” A.D. 1898, forms large whitish colonies, with irregular contour spreading on the surface of the gelatin, the bacilli being very small, mostly occurring in pairs, but sometimes joined together in thread-like forms. The second organism, called by me “bacillus e,” forms small brownish-yellow boat-shaped colonies on gelatin plates. The bacteria consist of plump cells two or three times the size of bacillus d, united in pairs and chains, but the cells vary considerably in size, and are surrounded by a capsule. I have discovered that the above bacteria, when used separately as pure cultures, exert little or no action on the skin, but when used together the action is very remarkable.

The gelatin and gelatin plates referred to in the above description are the gelatin and gelatin plates used for the cultivation of bacteria, according to the ordinary bacteriological methods as described in GÜnther’s “Bakteriologie,” published by George Thieme, Leipzig, in 1898, and in other text-books.

In the accompanying drawings, made from photographs which are of record in this case, the bacillus d is shown in Fig.21, and the bacillus e in Fig.22, both photographs showing the bacilli magnified 1000 diameters.

A culture may be prepared from the sweating bacteria by taking the hair from the skin when it “slips”—that is, when it can be removed by simply pulling it. The root portion of the hairs are then cut off, and about 10grm. carefully digested in 100c.c. of water at a temperature of 32° to 35° centigrade for several hours. The liquid portion is then poured off, and used for inoculating 10,000 c.c. of a nutrient medium of the character hereinafter described. The inoculated nutrient medium is then maintained for three days at a temperature of 37° centigrade, and may then be used for the inoculation of a larger quantity of nutrient medium.

Theoretically, a single cell of a bacterium is sufficient to inoculate any quantity of any suitable fluid; but in practice it is found necessary or expedient to employ 5 or 10 per cent. of inoculating matter to the volume of the liquid to be inoculated. The inoculation of the 10,000c.c. of nutrient medium may be done in a Carlsberg vessel, as described by Hansen in his “Untersuchungen aus der Praxis der GÄrungsindustrie.”

It is desirable that the nutrient medium should be without sugars or carbohydrates; and, although its composition may be varied, good results can be obtained by ordinary bacteriological methods, by using a medium composed of gelatin, 50 parts or 20grm.; potassium or sodium phosphate, 1 part or 0·4grm.; sodium chloride, 1 part or 0·4grm.; water, 2500 parts or 1000c.c. This medium, after inoculation, is maintained at a temperature of 37° centigrade, until the required bacterial action is completed, i.e., until the whole of the nutriment for the bacteria is exhausted, at which time the maximum quantity of the required enzymes has been produced. The time required for this action is not less than three days, nor more than seven days. The exhaustion of the nutriment may be ascertained scientifically by a microscopic examination of the liquid, the bacilli at this period commencing to form spores. To each litre of this liquid there is then added from 2 to 6grm. of lactic acid, and the acid liquid is afterward neutralized by ammonia, which is added when the liquid is to be used as a bate, the addition of the ammonia forming certain chemical compounds similar to those found in the dung. Instead of lactic acid, acetic or other similar organic acid may be used, but sulphuric or mineral acids must not be used. The addition of the acid to the liquid will immediately stop the growth of the bacteria; but the acid is not added for that particular purpose, but for the formation of the chemical compounds above referred to.

The above-described method is most suitable, when the bate has to be kept for a time before being used, or when it is desired to concentrate it for transit or export; but if the bate is to be used immediately, it may be prepared as follows: 100 parts of gelatin are dissolved in 1000 parts of water, and there is then added 50 parts of commercial lactic acid. The mixture is then heated, in a closed vessel, to 100° centigrade, by which operation the gelatin is partially peptonized, and the subsequent bacterial action is hastened. The acid liquid is afterward neutralized with ammonia, or other alkali, and the whole diluted with water to 20,000 parts. The dilution may conveniently take place in the wheel or paddle in which the bating is to be done, and to the liquid thus obtained there is added from 5 to 10 per cent. of the active culture from the Carlsberg vessel, as above described. The liquid is then allowed to stand for 15 to 20 hours at a temperature of 37° centigrade, and is then ready for use.

For bating skins in a practical manner with the improved bate herein set forth, the method of using the same is varied, according to the skins to be treated and the kind of leather it is required to produce, and the strength of the bate is varied in exactly the same manner as the strength of a dung bate, and such variation is made according to the judgment of the tanner, the improved bate acting in the same manner as a dung bate.

For kid-skins, calf-skins, skivers, and other skins for which dog dung has hitherto been used, the skins, after the liming process, are first well washed in water in the usual way, to remove the bulk of the lime. The skins are then placed in a wheel or paddle, with the bate prepared, as above described, with the acid exactly neutralized, or so nearly neutralized, that the alkaline action of the skins will complete the neutralization, all skins being alkaline when introduced into the bate. The bate is maintained at a temperature of 37° centigrade, and the skins are kept in motion until they have “fallen” considerably, i.e., until the swollen condition of the fibres due to the liming has disappeared. The skins are then removed from the wheel or paddle and scudded by hand or machine, preferably on the grain side, and the skins not sufficiently reduced are returned to the paddle, and the bating continued until the action is completed, this being judged in the usual way by the tanner by the feel of the skins. The strength of the bate, when skins are returned thereto, may be varied from the original strength, if desired, and after the bating is completed the skins are treated in the usual manner.

The strength of the bate into which the skins are placed, is varied according to the amount of liming the skins have undergone—that is to say, for a high-limed skin a strong bate is required. For moderately-limed skins the bate may be of such a strength that each litre as prepared for use contains five grm. of the original gelatin contained in the nutrient medium, which is equal to one part of liquid in which the culture has taken place to three parts of water. When the bate is prepared for immediate use, its strength is varied in the paddle as required. For very hard skins, such as goat-skins, the culture may be used as a bate undiluted or it may be diluted with an equal quantity of water.

For light-dressing hides and similar skins, which have hitherto been treated with pigeon dung, the skins are washed in the usual manner after the liming process, heated to 37°C., and placed in a wheel or paddle containing the improved bate, preferably in an acid condition—that is, before the ammonia or alkali has been added—the strength of the bate being equivalent to five grm. of original gelatin contained in the nutrient medium to each litre of the bate used. When the lime has been removed from the skins by the bate, which will be in about one hour, a quantity of the original culture previously neutralized with ammonia or other alkali and equal to about one-half of the quantity of the original culture first added is placed in the wheel and the bating continued until the process is completed, this being judged by the feel of the skins. If in the above method the chemical reaction of the bate be examined before the second portion of culture be added, it will be found neutral, and the action of the enzymes takes place in a neutral or alkaline solution, as in the first-described method.

The character of the principal enzyme in dung and in the improved bate is a proteolytic one; i.e. it resembles the trypsin contained in pancreatic juice.

Instead of adding an organic acid and neutralizing it by an alkali, as described with reference to both processes, there may be added an organic salt of the same character as that formed by the combination of the acid and the alkali.

Claim.—1. A bating liquor or bate containing enzymes of the same character as the enzymes contained in dog dung, an organic acid, and an alkali, or their chemical equivalent, i.e. an organic salt substantially as herein set forth.

2. A bating liquor or bate containing enzymes of the same character as the enzymes contained in dog dung and produced by fermentation an organic acid and an alkali, or their chemical equivalent substantially as herein set forth.

3. A bating liquor or bate containing one or more enzymes of the character of the enzymes contained in dog dung, an organic acid and an alkali, or their chemical equivalent substantially as herein set forth.

4. A bating liquor or bate containing one or more enzymes of the character of the enzymes contained in dog dung, or produced from bacteria obtained from dog dung, an organic acid, and an alkali or their chemical equivalent substantially as herein set forth.

5. A bating liquor or bate containing enzymes of the same character as the enzymes contained in dog dung, two to six grm. of an organic acid to each litre of the liquid and neutralized by an alkali substantially as herein described.

6. A bating liquor or bate containing enzymes of the same character as the enzymes contained in dog dung, from two to six grm. of lactic acid to each litre of liquor and neutralized by ammonia substantially as herein described.

7. A bating liquor or bate containing enzymes of the same character as the enzymes contained in dog dung and obtained from bacteria found on the roots of hairs during the sweating process, from two to six grm. of lactic acid, and neutralized by ammonia substantially as herein set forth.

8. A bating liquor or bate containing enzymes produced from bacteria obtained from dog dung and cultivated in a medium composed of fifty parts of gelatin, one part of potassium or sodium phosphate, one part of sodium chloride and two thousand five hundred parts of water, two to six grm. of lactic acid to each litre of liquor and neutralized by the addition of ammonia substantially as herein described.

Oropon (German Patent 200,519, July 21, 1908).—Process for Bating Hides. Dr. Otto RÖhm, Esslingen a/Neckar. In the present process, a watery extract of the pancreas in combination with ammonia or alkaline salts or mixtures of these salts is used as a bate liquor. The object of the process is to replace the dung bate. From the researches of Wood145 also Jettmar146 it appears that the peculiar behaviour of the dog dung bate is to be attributed to the action of enzymes in combination with organic amine compounds and ammonia salts. Starting from the assumption that other enzymes, known to have an action on hide substance, might have an analogous action to the dog dung bate, the author discovered that the trypsin of the pancreas had exactly the same bating action as the enzymes of dog dung. The action is aided by the fat-splitting enzyme of the pancreas, steapsin, which saponifies the fat in the hides.

A good bating action is obtained by a watery extract of pancreas, by the addition of an ammonium salt, which changes the caustic lime (from the limed pelt) into a soluble lime salt, and gradually reduces the alkalinity of the bate liquor caused by the lime in the skins, since the ammonia liberated by the lime escapes to a great extent from the liquor. The favourable action of the ammonium salt on the skins causes them to fall and become thinner, nor do they become rough when placed in clean water after bating, as a strongly alkaline skin will if placed in water containing calcium carbonate.

For example, the process may be conducted by extracting a pancreas weighing about 250grm. with 1 litre of water, and adding 10c.c. of such extract to 990c.c. of a solution containing 0·15 per cent. ammonium hydrosulphide and 0·3 per cent. sodium chloride. Such a solution forms a very active bate. In place of the ammonium hydrosulphide, any other ammonium salt yielding a soluble lime salt may be used, e.g., ammonium chloride.

The pancreas extract used in the above process must be used in a fresh condition or preserved from putrefaction by the addition of some suitable preservative; if putrefied, and consequently acid, it will not work. The preservation of the pancreas may also be brought about by drying, and the bate liquor made from the dry material by putting it in water. No putrefaction occurs during the bating process. The action of the enzymes is favoured by the alkaline reaction of the hide.

Claim.—Process for bating hides, characterized by the use of a watery extract of the pancreas, with the addition of an ammonium or alkali salt which forms soluble lime salts, or mixtures of such salts to the liquid.

In an addition to the above patent, Dr. RÖhm proposes to soften the water used by adding the proper amount of clear lime water to it. Starch paste can also be used for the same purpose, or a mixture of lime water and starch paste.

In a further addition, a weak acid mixture, consisting of 0·05 to 0·1 per cent. lactic acid and 0·05 to 0·1 per cent. ammonium chloride, is proposed in place of the ammonium salt alone, since the evolution of free ammonia had been found to be detrimental to the skins.

Eberle’s English Patent (21,202, 1909).—Improved Process for Bating Hides. Efforts have been made for years to replace dogs’ excrement used in many cases in tanning as a bate, by other simpler products and methods which in particular shall have the advantage of greater uniformity and thereby act with greater certainty.

Now it has been ascertained that substances which are only solvents of lime, such as acids of inorganic or organic nature and their salts, form an incomplete substitute. It has been shown by Eitner, Wood and others that there are enzymes and bacteria to which dogs’ dung owes its specific or bating properties. The action of dogs’ dung is explained as one which liquefies or dissolves the skin substance, such as is otherwise only done by enzymes and bacteria.

Experiments in the laboratory and in practice have shown that it is not the dissolving action on the skin substance in the narrow sense which is desired in bating the derm with dogs’ dung, but in order to prepare the hide for the manufacture of a soft and elastic leather, the albuminous intercellular substances and more particularly the layers of fat lying at the roots of the hair, in the corium and in many cases also on the epidermis, must be dissolved and thereby the fibrils of the skin loosened. The highly solvent action of the dung bate on the skin substance means in very many cases a direct disadvantage by reason of the loss of leather substance.

Extensive experiments with the separate constituents of dogs’ dung have shown that with none of them employed alone can a satisfactory action be obtained. For the experiments, the organic and inorganic salts contained in dog’s dung were employed. Pure cultures of intestinal bacteria were also examined and also the intestinal juices, secretions of the gall bladder, of the pancreatic gland and secretions of the intestinal mucous membrane. The relatively best bating action was obtained with the secretion of the gall bladder; only a moderate bating action could be obtained with the juices of the pancreatic gland and the secretions of the intestinal mucous membrane. It was therefore very surprising to find and could not be foreseen that mixtures of these three secretions of the digestive apparatus alone exerted an excellent bating action, and that such mixtures not only formed a perfect substitute for the bate of dogs’ dung, but that they acted far better than the latter, without it being necessary, as was recommended elsewhere,147 to add lime-dissolving salts to the bate, or to take measures in any other manner for the removal of the lime from the water.148

The explanation of the effective action of such mixtures is evident from the following statements:—

Pancreatic juice contains three ferments, of which for our purpose trypsin, which decomposes albumen, and steapsin which decomposes fat, are the most important. Both ferments are contained as zymogens, that is to say in an inactive form, in the pancreatic juice. The latter therefore only gives an incomplete bating action. Gall contains ferments which have properties which are mainly fat decomposing, but are also albumen dissolving. Gall also contains the salts of gallic acids which have the power in a high degree of dissolving and emulsioning greases or fats, and among others have a great solvent action on the chloresterin contained in the skin, more particularly in the roots of the hair. As regards the fat-decomposing and dissolving action, gall is far superior to pancreatic juice.

The ferments of gall are, however, also capable of energising the action of the steapsin in the pancreatic juice as a fat-decomposing ferment, that is to say of imparting to the pancreatic juice, which in a pure condition has a very slight action on fat, a high capacity for decomposing fat.149

Finally gall in bating the derms may be of great importance inasmuch as its acids form easily soluble lime salts. Extensive experiments have shown that gall, as such, is adapted to dissolve a comparatively large quantity of lime. In hard water an addition of gall prevents the precipitation of calcium carbonate, and the roughening of the derm, which, for instance, has been noticed when pure bacteria cultures are employed, is prevented by the addition of gall.

The intestinal juice contains in addition to carbonates and alkalis, enzymes which again exert a slighter bating action on the hide than those of gall. The intestinal juice alone has a similar action to pancreatic juice, but if intestinal juice be added to pancreatic juice, the most powerful enzyme of pancreatic juice, namely the albumen-decomposing trypsin is energised, and only in this way does the pancreatic juice fully acquire the property of dissolving albuminous substances.150

The proportions in which such mixtures best develop their actions, are those which obtain in animal organisms; the temperature also especially plays a great part. The maximum temperature lies about 40°C.

From the above statements it is evident that it is possible to produce various actions with the juices of the pancreas, gall and the intestines, quite dependent on which are considered the most important in the bating. Similarly, as the proteolytic action of the mixture of the three juices may be increased or diminished by using larger or smaller quantities of intestinal juice and pancreas, the fat-decomposing and fat-dissolving action of the mixture may also be increased or diminished by using larger or smaller quantities of gall, and of gall and pancreas respectively. Finally the quantity of the gall to be added is decided according to the amount of lime contained in the water employed in the bating. Experience has shown that a relatively small addition of gall will act very advantageously.

It must be especially remarked that artificial bates made in this way are extremely cheap as compared with the natural dogs’ dung, as gall and intestinal juice may be procured at very low prices and a considerably smaller quantity of the energised, more expensive, pancreatic juice is necessary than, for instance, would be necessary if this juice were employed in a pure condition.

The advantage of this invention also consists in its being possible to make better bates than that which is made, for instance, from dogs’ dung because, as hereinbefore stated, it is a disadvantage of this latter bate that it in many cases dissolves too large a quantity of the albuminous substance. Otherwise, the composition of the improved bate quite coincides qualitatively with the composition of dogs’ dung, as the latter actually consists in addition to the unabsorbed portions of food, of secretions of gall, the pancreatic gland and the mucous membrane of the intestines. The trypsin and steapsin respectively as well as being derived from the pancreatic juice, may also be derived from the vegetable kingdom, for instance, there are considerable quantities of trypsin in the sap of the fig. Steapsin, in not inconsiderable quantity, is found in the saps of flax, hemp, maize, etc.

It must also be remarked that the colouring matters in gall are of quite subordinate importance, and may be disregarded. The view formerly adopted that the colouring matters in gall stain the leather is incorrect.

Example:—200 c.cm. of gall juice in 1 litre of water are mixed with the watery extract of 200grm. of chopped small intestine in 1 litre of water on the one hand, and 100grm. of the pancreatic gland in 1 litre of water, on the other hand. This watery solution is added to the bating bath, according to the bating action desired. It can also, in order to allow of being more easily handled, be obtained in solid form by absorption in sawdust or kieselguhr and drying at 30° to 40°C.

Claim.—A process for bating hides, characterised by the use of mixtures of gall, the secretion of the pancreatic gland and intestinal juice, and by the use of mixtures of the active enzymes in these, or active enzymes derived from the vegetable kingdom, substantially as described.

Prof. Dr. H. Becker’s English Patent (24,982, 1910).—Improvements in Puering and Bating Hides and Skins.—It has been shown by Wood, of Nottingham, and by Dr. Popp and Dr. Becker, of Frankfort-on-the-Main, that the action of a good puer or bate on hides, is connected with the development of certain species of bacteria.

The preparation of pure cultures of these bacteria (which are derived from dog dung) has enabled what may be properly termed a safe puer to be obtained, inasmuch as by its use overpuering the hides is entirely prevented. Furthermore, the leathers are fuller and do not lose any excess of hide substance, so that a dozen sheepskins that have been suitably puered by the bacteriological method, will weigh about 9 ounces more than a dozen skins of the same kind and origin, that have been treated in exactly the same way in other respects, but puered with dog dung.

The method of action of the bacterial puer has been elucidated as follows. The bacteria present in the puer are microscopically small and pass easily into the skin through the pores of the latter, while on the surface and in the substance of the skin they produce their metabolic products and enzymes. These substances are partly proteolytic, partly fat decomposing, and also diastatic in character, so that the highly proteid intermediate substance of the skin is degraded. By means of the ultimately formed ammonia, amine bases and ammonium bases assisted by the action of organic acids produced by the bacteria, the lime soaps are decomposed. Lime and fat are partially dissolved, and partially further decomposed or converted into a form which enables them to be worked out by mechanical means. At the same time the roots of the hairs are also loosened so that the hairs also can be readily removed by mechanical treatment.

Another essential factor is the liberation of gases formed within the skin by the action of the micro-organisms and exerting a very gentle pressure on their environment. The structure of the fibres is loosened, the fibrils are straightened individually without sustaining any important loss of corporeal matter, and in this way a firm, tough and yet soft handling leather is obtained. Attempts have been made to improve this puer by adding, for instance, organic acids and salts to the bacterial cultures.

Other methods of puering, based on the direct weakening of the skin fibres from the outside, may also effect the pulling down of the hides, and moreover, in consequence of that attack on the skin fibres without straightening the fibrils, an immoderate amount of substance is lost, and therefore a hard, stiff, thin and light leather is obtained.

To this class belong also the purely digestive puers such as pancreatic juice, intestinal juice and the like, or purified enzymes. These enzymes are colloidal and therefore incapable of diffusion, and consequently they digest the hide mainly from the surface, that is to say, the grain side and inner side of the hide. The fibres, in-so-far as they are accessible at all to the action of the colloidal enzymes, are removed from outside without the fibrils being loosened and straightened. Hence they are weakened by the digestive puer to such an extent that the hides seem to be gradually pulled down; but the skin will by that time have lost too much substance, so that, inter alia, even the grain appears to have been corroded. In this way the leather is rendered thinner and lighter than that from the dung or bacterial puer—a defect manifest to every expert.

This danger is particularly great when, by the artificial admixture of corporeal juices, complications are set up, that intensify the destructive action of the digestive enzymes on the material, and when their supplementary action is not suitably controlled.

These animal or digestive enzymes and fat decomposing substances originate, in-so-far as they are not of vegetable origin, for the most part in the upper portions of the digestive tract. The use of these substances effects an imitation of the purely enzymatic and fat decomposing processes that go on in the upper part of the intestines, but omits the processes—not less important for digestion and the formation of excrement—occurring in the large intestine and the adjoining portions of the digestive tract. Here the bacteria and the vegetable enzymes secreted thereby, play the chief part. They decompose not only the food constituents—partly by putrefaction—but also the albuminoid digestive secretions and the gall, so that only small quantities thereof are left. Hence when applied to the puering process, the use of bacteria, together with their specific enzymes and metabolic products, is equivalent to a restriction of the immoderate digestive action of the pancreatic and digestive juices, i.e. of the animal enzymes.

Digestion therefore, with the resulting formation of excrement, is carried on with the accompaniment of a mutual control, excitation and restriction on the part of the digestive secretions and the bacterial phenomena.

These latter form the real basis of the puering of hides in dung preparations.

This is also evident from the purely practical experience that dog dung puer, e.g. for glove leather, is essentially improved by leaving the dung to ferment for several weeks or rather months. During this process an increase occurs in the micro-organisms present, and also in their metabolic products and enzymes, but not in the digestive juices originating in the organs of the animal body—the term “digestive juices” being restricted to indicate only such juices as are produced in the course of the digestive tract by the organs and cells of the animal body, in contradistinction to the juices produced by bacteria.

According to the present invention, the bacterial cultures, together with their metabolic products or products of digestion and enzymes, are used in combination with one or more of the substances that are excreted in the digestive tract by the animal body itself in order that not only each of these substances may exert its special action on the skin, but also that the aforesaid mutual influencing, and more particularly regulating of the action may take place.

On this principle, in preparing an artificial puer for hides, and in accordance with the nature and preliminary treatment of the raw material, and the requirements put forward in respect of the finished product, the bacterial puer, nutrient medium or culture is mixed with the corresponding digestive juices, or with purified animal or vegetable enzymes, as well as with fat decomposing media, if necessary, such as ground castor-oil seeds, hemp seed or the like, or with extracts of same, or with gall. Where it seems necessary, substances capable of dissolving lime may also be added, for example, sugar, molasses, salts of ammonia, organic acids, or the corresponding salts or the like.

Finally, also, the several operations may be carried out independently of one another, it being in such case again advisable to adhere to the processes going on in the intestines.

If, for instance, specially hard goat skins are to be pulled down strongly by puering, it is advisable to add to the nutrient medium of the bacteria a little papayotin or papain, either—according as rendered necessary by the local conditions—in the preparation of the bacterial puering liquor, or during the propagation of the bacteria. If the fells are less hard so that less pulling down is required, the hides are first treated with a weak solution of the digestive ferments, and then with the bacterial liquor. In this way excessive digestive action is counteracted in good time.

Sheep and goat skins that are particularly rich in fat are immersed in a bacterial puering liquor, containing ground castor-oil seed or castor-oil cake in suspension. The fat-decomposing ferment contained in this meal then comes into immediate action, and the liberated fatty acids form readily soluble soaps with the ammonia, originating from the degradation of the proteid substances, and with the allied bases.

Extensive practical experiments have also shown that, in the case of very fat skins, the action of the bacterial puer is increased by mixing a suitable salt of sulpho-ricinoleic acid with the puering liquor, or by washing the skins with solutions of similar soaps either before they are immersed in the puering liquor, or subsequently.

Local conditions, and the requirements laid on the finished leather, must decide which of these methods is specially advisable.

In any event, however, the combinations of the bacterial puer afford a means of obtaining an increased puering effect in many cases where puering with the separate auxiliaries mentioned does not produce a sufficient result.

Claim.—In the method of puering hides wherein bacterial cultures, their metabolic products and enzymes are employed, the combined use with these agents of digestive juices, mixtures of digestive enzymes or pure digestive enzymes (and, if desired, of fat-decomposing substances), either simultaneously with said agents or subsequently thereto.