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THE LEATHER INDUSTRY. 
the hair may simply be rubbed off, and this is done on a suitable 
machine. Sometimes arsenic sulphide is used instead of sodium sul- 
phide to “sharpen” the limes, and similar use has also been made of 
lye and of ammonia. In earlier times lime was used alone, but the action 
of pure lime liquors is extremely slow, and satisfactory results were 
obtained only with old liquors that had become heavily charged with 
decomposition products of the hides, and probably also with bacteria. 
Another method, once widely used, was to put the hides into a warm 
chamber where the epidermis was destroyed by putrefaction. | Where 
GRAIN SURFACES OF GOAT SKIN (A) AND CALF 
SKIN (B) (%* 8). , 
the cost of labour has been large compared to the value of the hair, 
some tanners have employed strong solutions of sodium sulphide alone 
to destroy the hair, the hides being practically free from hair and 
epidermis when hauled from the vats. An unhairing action can also 
be produced by dilute solutions of ammonia and by pancreatic enzymes. 
All of the processes mentioned leave something to be desired, and the 
whole subject of unhairing is in need of a much more thorough inves- » 
tigation than has yet been made. 
DeLiMrIna. 
Two more general processes complete the preparation of the hides, 
for tanning: the removal of lime or other alkalis from the hides and a 
curious process known as “bating.” The bulk of the lime is removed 
simply by washing, and the remainder, which has either carbonated or is 
combined chemically with the hide protein, is removed by treatment 
‘with dilute acids or is sometimes allowed to remain in the hides until 
removed by the acids present in the tanning liquors. , 
Barina or Purrra. 
Bating, or puering, originally consisted in putting the hides into vats 
containing a warm infusion of the dung of birds or dogs and leaving 
them there until the “ plumping” action of the lime liquors had been 
counteracted and the hides had become soft and raggy. Just how the. 
early tanners hit upon this process is a matter for speculation, but the 
fact remains that the method appeared to be necessary to get certain | 
desirable results in the leather. Investigations, notably that of J. T. 
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