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 Wood[145] also Jettmar[146] 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 250 grm. with 1 litre of water, and adding 10 c.c. of such extract to 990 c.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.