‘7 
a, 
THE LEATHER INDUSTRY. | 
acidity is markedly increased by adding neutral chlorides, such as com- 
mon salt, and is decreased by neutral sulphates. They showed also 
that neutral salts have a similar action upon solutions of hydrochloric 
acid or sulphuric acid. It is quite evident, then, that before we can 
hope to control every factor in chrome tanning we must learn more 
about pure solutions of acids and salts. It is in further studies .of this 
kind that the pure chemist can be of very great service to the industry, 
and it is desired that he should appreciate the possibilities for applying 
his discoveries. An increase in the acidity of a chrome liquor retards 
the tanning. The addition of sodium chloride increases the acidity, 
and, as would be expected, retards the tanning. On the other hand, 
the addition of sodium sulphate decreases the acidity, but it also retards 
the tanning. The explanation of these facts surely lies within the 
province of the pure chemist. 
The writer has done much work on theories of tanning, and believes 
that vegetable tanning consists of the combination of collagen and 
tannin, yielding collagen tannate or vegetable leather, and that similarly, 
in chrome tanning, we have the formation of a chromium collagenate, 
collagen being amphoteric. On this basis the combining weight of 
collagen appears to be 750, or some multiple or submultiple of 750. 
This view has been contested, but its truth or fallacy should interest the 
pure chemist. ; i 
; Parrrquorine any Srurrrna. 
After tanning, by either the chrome or vegetable process, the hides 
are fatliquored or stuffed. Fatliquoring which is applied to light 
leathers consists in drumming the leather with a hot emulsion of suit- 
able oils. If the condition of the leather is right and the proper 
quantities of materials have been used, the leather will remove 
Dyed 
m----Grain ~ 
& Surface 
Dyed 
r---Flesh . 
Surface ~ 
VEGETABLE TANNED CALFSKIN (= 40). 
