72 ON THE ART OF TANNING. 



According to thefe properties, could I doubt that this was 



pure tanin ? certainly not* fince it prefents the fame remits as 



that obtained by the procefs of Mr. Prouft. 

 How obtained If we wifh to obtain more pure tanin than that which is 

 P urc# obtained after the folutionof the lime of the tanate of this fub- 



fiance by an acid, the infufion in alcohol may be evaporated, 



and we (hall then have very pure tanin. 



The muriatic acid has prefented me with the fame refult as 



the nitric. 



Cortje&ures that The rapidity with which the upper leathers of fhoes (cuir» 



lime water is ad- d'emptisrne) are tanned, according to the procefs of Citizen 

 vantageous m •■., . ° . 



taning by the Lequin, who, in manufacturing them, contents himfelf with 



lime combining merely fubjecting them to 4he preparations of warning and 

 flefliing by lime water, without fuffering them to fwell, and af- 

 terwards tans them, led me to prefume that in this cafe a com- 

 bination is effected of tanin with the lime contained in the 

 fkin thus treated, befides the combination of the tannin with 

 the gelatine contained in the fkin, which accelerates this fa- 

 brication. May it not be probable according to this notion, 

 that the fabrication of leather would be accelerated, if after 

 having fubjecled the (kins to the operations of wafliing and 

 flefliing in lime water, they were left to fwell in the fpent ooze 

 or water in which the old bark, w T hich has already ferved for 

 tanning leather, has been infufed. In this cafe, the fmall 

 quantity of tanin dilfolved in this water would combine with 

 the lime with which the fkin would be charged in proportion 

 to the working, and would form a tanate of lime. The fwel- 

 ling would perhaps be effe&ed by this means with a little lefs 

 celerity than by the fulphuric acid, but then it would perhaps 

 be preferable, from the circumftance that the fkin in fwelfing 

 would begin to charge itfelf with tanin, whereas by the ful- 

 phuric acid, the lime with which the fkin is impregnated, 

 when worked, — this fubftance diifolved in water, the lime, I 

 fay, combines with the fulphuric acid employed to (well it, 

 which, I prefume, muft give to the leather a brittle quality 

 that it would perhaps not have if the other procefs were 

 ufed. Perhaps alfo, after the fkins have fwelled in the ooze, 

 this completion might be haftened by putting them firfl into the 

 folution of tan, as Cit. Lequin does, and afterwards fteeping 

 them alternately in lime water and in infufion of tan, always 

 taking care to leave them but a fhort time in the lime-water, 



which 



