Nfw Pneefs of Tanning. tf 



water. The prcfcncc of this prhiciple is afcertained by its ftrlking a black colour when added 

 to a fmall quantity of the folution of vitriol of iron or green copperas. As foon as the water 

 ■from the digefter ceaies to exhibit this fign, the tan is exhaufled, and muft be replaced with 

 new. 'I he gallic lixivium is referved for the purpofe of taking the hair off from hides. 



Strong hides, after wafliing, cleaning, and flefliing, in the ufual'way, are to be immerfcd. 

 for two or three days in a mixture of gallic lixivium and one thoufandth part by meafure of 

 ilenfe vitriolic acid *. By this means the hair is detached from the hides, fo that it may 

 be fcraped off with around knife. \Vhen fwelling or raifing is required, the hides are to 

 be immerfed for ten or twelve hours in another vat filled with water and one five-hundredth 

 part of the fame vitriolic acid. The hides being then repeatedly waflied and drefled, arc 

 ready for tanning ; for which purpofe they are to be immerfed for fonie hours in a weak 

 tanning lixivium of only one or two degrees ; to obtain which, the latter portions of the 

 infufions are fet apart ; or elfe fome of that which has been partly exhauftcd by ufe in 

 tanning. The hides are then to be put into a ftronger lixivium, where in a few days 

 they will be brought to the fame degree of faturation with the liquor in which they are 

 immerfed. The (trength of the liquor will by this means be confiderably diminifiied, and 

 muft therefore be renewed. When the hides are by this means completely fiturated, that 

 is to fay, perfectly tanned, they are to be removed, and flowly dried in the fliaJe. 



Calf-fkins, goat-ikins, and the like, are to be fteeped in lime-water after the ufual flefli- 

 ing and wafliing. Thefe are to remain in the lime-water, which contains more lime than 

 it can diflblve, and requires to be ftirred feveral times a-day. After two or three days, the 

 Ikins are to be removed, and perfe£lly cleared of their lime by wafliing and prefilng in 

 water. The tanning procefs is then to be accompliftied in the fame manner as for the 

 flrong liides, but the lixivium muft be confiderably weaker. iVIr. Defmond remarks, that 

 lime is ufed inftcad of the gallic lixivium for fuch hides as are required to have a clofe grain; 

 becaufe the acid mixed with that lixivium always fvvells the fkins more or lefs ; but that it 

 cannot with the fame convenience be ufed with thick fkins, on account of the confiderablc 

 labour required to clear them of the lime, any part of which, if left, would render 

 tliem harfh and liable to crack.' He recommends, likewife, as the bcft method to bring the 

 M'hole furface of the hides in contact with the lixivium, that they fliould be fufpended ver- 

 tically in tlie fluid by means of tranfverfe rods or bars, at fuch a diftance as not to touch 

 each other. By this praftice much of the labour of turning and handling may be faved. 



IMr. Defmond concludes his fpecification by obferving that in fome cafes it will be ex- 

 pedient to mix frefli tan with the lixivium; and that various modifications of ftrength and 

 other circumftances will prefent themfelves to the operator. He affirms that, in .addition 

 to the great faving of time and labour in this method, the leather, being more completely 

 tanned, will weigh heavier, wear better, and be lefs fufceptible of moifture than leather 

 tanned in the ufual way ; that cords, ropes, and cables, made of hemp or fpeartery im- 

 pregnated with the tanning principle will fupport much greater weights without breaking, 

 be lefs liable to be worn out by friiStion, and will run more fmoothly on pulleys; infomucli 

 that, in his opinion, it will render the ufe of tar in many cafes, particularly in the ritTtinrr of 

 fliips, unnecefTary ; and, laftly, that it may be fubftituted for the prtfcrvation of animal food 

 uiftcad of fait. 



• Miii.inj; CG degrees on the hydrometer for acid?. Sp. gr. i.f 4S of Bjuhic. 



E 2 The 



