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 5 oz. to 9 oz. are required per 100 lb. 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:—
| Ammonium butyrate | 1 | grm. |
| Castor oil seed meal | 2 | " |
| Dry pancreas | 0 | ·01 " |
| Water | 1000 c.c. | |
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 0·5 c.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 (70/100 c.c. liquor pancreaticus per 1000 litres).
Castor oil seed contains a lipatic enzyme, and when shaken up with olive oil will emulsify the oil. 75 grm castor oil seed meal, and 10 c.c. of olive oil were shaken up with 490 c.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.