go THE SCIENTIFIC ASPECTS OF TANNING. 



cessors were accustomed to keep their hides in the lime pita for as 

 many months as we do days. If so, their treatment must have 

 been homoeopathic. A certain amount of decomposition appears 

 necessary to insure elasticity to the future leather ; but to ascertain 

 the exact stage in the decomposition when its action should be 

 arrested is the all important question. We believe in the majority 

 of cases more lime is used than necessary for the purpose, which 

 is not only a loss to the tanner, but rendering the future leather 

 dark in color and brittle in wear. 



Prejudice has a great deal to answer for in this matter. When 

 we reflect that lime is only soluble in water to the extent of i8 

 grains per gallon, all in excess of that amount can only exert its 

 caustic properties injuriously on the exterior of the hide. The 

 time taken for the process of unhairing for ox hides being from 

 14 to 21 days. Cool -sweating, as adopted by North American 

 tanners, is better adapted for dry hides than for salted ; and has 

 only with one exception, so far as we know, been practically 

 worked in this country. 



Charcoal has been used in the depilation of hides, and, judging 

 from our own experience, is likely to be more generally employed. 

 The theory of its action is stated to be this : — The oxygen con- 

 tained in the pores of the charcoal unites with the carbon of the 

 grease in the glands at the roots of the hair and other portions of 

 the skin, forming with the hydrogen of the water some form of 

 hydro-carbon, which passes off, inodorous and imperceptible ; in 

 fact, a process of combustion takes place within the pores of the 

 hide. Charcoal does not raise or swell the hide, — one great 

 objection to its use 5 but that it will effect the depilation of a hide, 

 without any perceptible trace of ammonia, is no longer a matter of 

 doubt. 



Sulphate of Sodium has been lately brought under the notice of 

 the trade. Though said to be used in Germany, we are not aware 

 that any quantity is employed here. Its very powerful action, 

 especially when placed in the hands of prejudiced workmen, will 

 account in some measure for its neglect. 



