ARTIFICIAL BATES.

As may be supposed, inventors have from very early times turned their attention to the substitution of some other material in place of the unappetizing one so long in use. But as I pointed out in a short article entitled “Rationale of Bating”133 many of them looked upon bating and puering as a process for removing lime from the skins, and nothing more; whereas we have seen that it is a very complicated process in which, not only is lime removed more or less effectively, but the skin fibres are acted upon, and portions of them rendered soluble, and the skin thus got into the necessary condition.

This misconception of the object of bating or puering prevented the success of most inventions of artificial bates up to quite recent times. Procter states that the use of ammonium chloride as a bate was patented by Zollikoffer in 1838. Such agents as this, and various acids, which have been proposed are merely chemical deliming agents, and, as such, we do not propose to discuss their use as artificial bates. Procter134 gives an excellent account of these processes, including one of his own, in which ammonium chloride is used in conjunction with metabisulphite of soda, and for successive packs sufficient sulphuric acid is added to neutralize the ammonia formed.

The same author135 also mentions an American invention for bating by the use of old lime liquors neutralized with sulphuric acid. This method is much more scientific than would at first sight appear, and more nearly approximates to the conditions of the dung bate than any of the early inventions. Old lime liquors contain much ammonia and weak organic acids, such as caproic, amido-caproic (leucin) and tyrosin. On adding sulphuric acid, the lime forms an inert sulphate, and the sulphate of ammonia and the weak organic acids which remain dissolved are just what are required in a chemical bate. The author has used this bate with success on certain classes of goods.

Tiffany’s bate, which is used in America, is composed of glucose and glue, and bates of this composition are also in use in England. As an example, 10lb. glucose and 1/2lb. of glue dissolved in 1000 gallons water, at a temperature of 75°F., and allowed to ferment for a few hours, may be used for the bating of bellies, and if used in a paddle or latticed drum will bring them “down” very rapidly.

Davis136 gives a list of twenty-nine patents for bating issued by the U.S.A. Government from 1790 to 1883 inclusive. I do not know whether any of these are in use at the present day.

Erodin.—Since the publication of the authors researches on the constitution and mode of action of the dung bate, renewed attention has been given to the construction of bates, or puers, having an identical action. One of these has been worked out by Professor Dr. H. Becker, of Frankfort o/M, in conjunction with the author under the name of Erodin (Latin, erodere, the equivalent of the German beizen—to bate).

As this was the first artificial bate in which a pure culture of bacteria has been applied to the treatment of skins, I propose to describe it in some detail.

Erodin137 consists essentially of a nutrient material in the form of powder and of a pure culture of B. erodiens which is added to the powder mixed in a definite quantity of warm water (40°C.). On the average about 10grm. of this material is sufficient to bate one kilo of wet prepared skin.

In practice it is found that this material acts far more energetically on the skins when living bacteria are present in the liquid; we suppose that they penetrate the skin and form their products in the intercellular spaces. It was found that, in the evaporation of the cultures to dryness, the bacteria were mostly killed or so far reduced in activity, that on preparing the bate after a certain lapse of time it was liable to become infected by foreign organisms.

In order to ensure uniform results a pure culture of the special bating bacteria is supplied with every 5 kilos of the erodin powder. The weighed amount of erodin is placed in a perfectly clean mashing-tub, with 50 times the weight of water at a temperature of 40°C. a pure culture of Bacillus erodiens is added to the mixture, and the whole covered with a clean cover and allowed to stand for two or three days. A little steam is admitted morning and evening so as to maintain the temperature at about 40°C., or some other suitable device for heating is applied. Several tubs may be kept in a small stove heated to the right temperature by steam pipes. In this way the bating bacteria develop rapidly, and if the proper precautions as to cleanliness and temperature have been observed, there is no fear of any adventitious germs getting the upper hand. As soon as a vigorous growth is attained, usually on the third day, the bate is ready for use.

Erodin is in use on a fairly large scale, and, as is usually the case, difficulties have arisen on a manufacturing scale which do not occur in the laboratory. In the practical application of the material the mashing-tub may be 3ft. 9in. in diameter and 3ft. 3in. in height and of a capacity of 200 galls. Steam is admitted directly by means of a copper pipe fitted with a boiling jet.

The goods are bated in the ordinary bating paddle or puer wheel (Fig.3, p.13).

During the year 1901 about 9000 dozens of sheep “grains” were puered with Erodin at Trent Bridge Works (Messrs. Turney Brothers, Ltd.) Nottingham, and considerable experience gained in its use.

The mode of operation was as follows:—On Fridays 30 kilos of Erodin powder was mashed in a wooden vessel in 1600 litres water at 40°C. and inoculated with a sufficient quantity of a pure culture of B. erodiens. The temperature was kept at 35°–40°C. by admission of a little steam first thing in the morning, again at noon, and in the evening, and the liquid so prepared was ready for use on Monday. One wheel or paddle was kept going for the work. To start the operation, 200 litres of stock liquor was put into the wheel, and sufficient water added for the goods to turn freely. The skins previously washed, as described in Chapter I., were paddled until sufficiently “fallen” or “down.”

For the following lots, the liquor was strengthened by the addition of 100 to 140 litres of the stock liquor, the wheel being run off and cleaned out once a week. The general result showed that “high-limed” skins and previously salted skins were more refractory to this bate than to dung.

As in the English system of collecting pelts there are all stages of liming, skins containing from 1.5 to 9 per cent. CaO on the dry skin, it is not surprising that considerable difficulty was experienced in keeping the puering uniform. Skins containing over 3 per cent. CaO on the dry skin, seem to require a real putrefactive action in order to “bring them down” sufficiently, or it may be that their alkalinity is too great to allow the bating enzymes to act properly. It may here be said that if the fibres of skin are actually damaged by excessive action of lime or any other chemical, no subsequent treatment is of avail to remedy the defects.

Shearling pelts were excellent when puered with erodin, a further proof that the alkalinity is of importance, since these pelts do not require so much lime as “old fells” to bring them into proper condition for splitting.

For sheep and calf skins treated from the market condition and consequently containing a uniform amount of lime—2–3 per cent.—the process is quite reliable, and is in practical use on a large scale. Goat skins have been successfully bated with erodin by treating them in a concentrated liquor in a drum,138 instead of a paddle, the mechanical effect of the drumming enabling the bate to penetrate the hard and compact skin, while the more concentrated solution of the enzymes attacks the so-called “beard,” and renders the skins as supple as sheep skins bated in a paddle.

It may be of interest to give here some of the results of the early trials of erodin in a tabular form, due to the late Franz Kathreiner. They are a further proof of the thoroughness with which he carried out all his work.

Leather, N.F. and Kalochrom. Date of Trial, Nov. 22, 1898.

Remarks.—22 skins of E 47 after 3 hours running had 250c.c. 70 per cent. lactic acid; they were marked with a hole in the tail; were more fallen than the others.

Judgment after Scudding.—All lots well down; E 47 whitest colour; all smooth grain, E 47 and B 3 smoothest. The 3 goat were not low enough.

It was observed both in laboratory experiments139 and in practical work that the presence of solid matter in the puering liquor had a considerable influence on the speed at which the goods fell. The clearer the liquor the slower the action. The explanation of this fact is not quite clear. Possibly the finely divided solid matter acts as a carrier for the enzymes, each particle offering a very extended surface, or it may be that the action of the solid matter is mechanical, like that observed in bran drenching.

The goods puered with erodin, whether split or unsplit skins, should be scudded on the grain. Sheep splits are scudded with a machine of Sir John Turney’s type. (Fig.6, p.17.) Roans and goat may be scudded with any of the spiral knife machines (Turner, Moenus, etc.) in general use.

The following figures, p.187, giving the reactions of an erodin bate in c.c. N/5 alkali or acid required to neutralize 50c.c. filtered bate, are of interest as being taken from actual work. They were kindly communicated to me by Herr Karl Schorlemmer, chemist to Messrs. Doerr and Reinhart, of Worms.

Erodin, tested by the electrometric method, was found to have the following hydrogen ion concentrations:—Paddle before goods, p = 0·672 volt, equivalent to a hydrogen ion concentration p+H 6·6. The same liquor after goods, p = 0·710, equivalent to p+H 7·3. Compare puer liquors, p.79.

Oropon.—An interesting application of the theory of the bating process which was put forward by me140 is that of Dr. Otto RÖhm141 in 1908, in which, instead of a bacterial culture, he employs an infusion of pancreas in conjunction with ammonium salts. This bate has been put upon the market in the form of a powder under the name of Oropon.

The approximate composition is:—

The nitrogen unaccounted for by ammonium chloride is 0·32 per cent.

Its chief advantage is the simplicity of application, no previous fermentation being required. About 5oz. to 9oz. are required per 100lb. wet pelt, and it is recommended to soften the water by adding a certain quantity of clear lime water to it previous to making up the puer.

Its disadvantages are, that unless a previous bath is used, the quantity of ammonia given off is detrimental to a proper bating action, so that for good working a preliminary bating is required. Another disadvantage is that the whole of the enzymes being in the bate their action is more superficial and the grain may be puered too much while the interior of the skin is not penetrated by the enzymes.

The author has made some experiments with an enzyme bate using ammonium butyrate instead of ammonium chloride, and castor oil seed meal in place of the wood fibre.

It was found that the amount of ammonium salts in solution in the most effective bate was approximately one gram per litre. The bating liquid was therefore made up as follows:—

This liquid at 40°C. bated a skin well in one hour. On increasing the quantity of castor oil seed meal to 4 grm. per litre, the bating effect was not so good. Substituting 0·5c.c. liquor pancreaticus (Benger) for the solid pancreas, the bating effect was too powerful, the thinner skins were attacked by the bate, and the grain destroyed in patches in a very similar manner to over-puered skins. Further experiments showed that a little more than one-tenth of this amount of pancreatic solution per litre would be sufficient (70/100c.c. liquor pancreaticus per 1000 litres).

Castor oil seed contains a lipatic enzyme, and when shaken up with olive oil will emulsify the oil. 75grm castor oil seed meal, and 10c.c. of olive oil were shaken up with 490c.c. of water and formed a perfect emulsion, no fat being visible on the surface of the liquid. The mixture was diluted to 7 litres, and a grain treated in it at 40°C. for half an hour; it was fairly well bated in this time, and had a smooth slippery feel, such as skins have in the puer, but was perceptibly “higher” than the skins bated in the new bate containing pancreatin.

This experiment appears to confirm the fact that a mixture of enzymes is necessary, or, at any rate, that a lipatic enzyme alone is insufficient for complete puering.

Dermiforma.142—This is an American preparation, put on the market by the Nowak Manufacturing Co. of Chicago, and is described as a natural bacterial liquor of organic acidity. For 1200lb. scudded calf skins, 9 gallons of the liquid Dermiforma are used at 100°F., one-third being put in to start with and the remainder added gradually; time required, about 3 hours. For sheep skin a less quantity is required. This bate was found to be a preparation of whey, and contains a certain quantity (18–20 per cent.) of lactic and other organic acids, produced by fermentation; it is therefore to be classed as a drench, and is not a true bate or puer, since tryptic ferments or bacteria are not present.

Puerine.—Another bate, manufactured in America is advertised under the name of Puerine, “the long-looked-for bacterial bate.” The manufacturers give the following directions for use. To start a bating liquor, 10lb. of the dry powdered puerine is put into a half barrel of warm water (100°F.), and allowed to stand for 3 or 4 days, maintaining the temperature by occasionally warming the infusion with a steam pipe. This amount is sufficient for each 100 galls. water in the bating vat or paddle wheel, and will bate as many skins as can be turned in 100 galls. When the warm infusion of puerine has stood the required length of time, in order to generate the necessary bacterial ferments, the bating vat is run up with warm water say, 100 degrees in warm weather and 110 in cold weather, and the infusion of puerine, including the undissolved portion, is added to the bating vat, and the skins entered into the bating liquor. As the action of the puerine on the skins is exactly the same as a dung bate, the judgment of the operator must determine when the skins are “low enough.” It is not necessary to make a fresh bating liquor for each pack of skins, because the bating liquor improves with age. With each succeeding pack of skins, enough warm water is added to the bating vat to make up for the loss of liquor which is occasioned by the removal of the previous pack, and from 3 to 5lb. of puerine for each 100 galls. added directly to the bating liquor; it is then in condition immediately to use again.

The bate was found to consist of

As it is allowed to ferment without the addition of bacteria, it will be seen that it acts in quite a different manner to erodin, being more of a modified drench than a true bate, and is not in any way a perfect substitute for the dung bate.

Sucanine.—This is a French bate, put on the market by Messrs. Muller and Co., Rouen; it is described as “concentrated dog puer, chemically clean, i.e., all foreign matters have been eliminated and it contains only that which is really necessary.” The directions state that the quantity to be used is the same as of dog puer prepared ready for use. The paddle is kept at a temperature of 30°C.

This material was found to be a liquid containing ammonium sulphide, phosphates and chlorides of sodium in solution, a considerable quantity of solid matter in suspension consisted of calcium phosphate and calcium sulphide. There was sufficient organic matter to permit of bacteria growing in the diluted liquid.

It had no harmful effect on skins and “brought down” most sheep skins in an effective manner; some resistant skins appeared to require further puering.

Purgatol is a patent bate put on the market by Dr. G. Eberle and Co., of Stuttgart. 1 3/4lb. is said to be sufficient to bate 100lb. wet pelt in 1–2 hours at 38°–40°C. It is a dark brown liquid with an unpleasant smell. When boiled with potash it gives volatile alkaline products.

Distilled with sulphuric acid it gives an acid distillate consisting of organic acids mostly of the fatty series. It contains amines and volatile nitrogenous bases, but no enzymes or bacteria. It must therefore be classed as a deliming agent and not as a true bate or puer.

“Esco.”—This recent artificial bate is of an acid character, and is said to have an action intermediate between the bran drench and pigeon dung; it contains no animal enzymes, but appears to contain some vegetable enzymes of a lipatic character; it also contains 18 per cent. of ammonium chloride in which respect it resembles “Oropon.” It is manufactured by E. Stickelberger and Co., Haltigen, near Basle.

Other artificial bates are treated of in the next chapter under the respective patents. There is also an interesting article on new bates by Eitner in Der Gerber, Nos. 878 and 879, 1911. See also Collegium, 1911, p.402.