206 TANNING. 



improvements have been made in the practice of 

 this art* M. Seguin, in France, has particularly 

 distinguished himself by his researches on this sub- 

 ject, and much improved the art in his country. 



In 1795, Mr. William Desmond obtained a patent 

 for practising Seguin's method in England. He 

 obtained the tanning principle, by digesting oak 

 bark, or other proper material in cold water, in an 

 apparatus nearly similar to that used in the salt- 

 petre works : that is to say, the water which has 

 remained upon the powdered bark for a certain 

 time, in one vessel, is drawn off by a cock, and 

 poured upon fresh tan: this is again to be drawn 

 off) and poured upon other fresh tan ; and in this 

 way the process is to be continued to the fifth 

 vessel. The liquor is then highly coloured, and 

 and marks from six to eight degrees upon the hy- 

 drometer for salts. This he calls the tanning lix- 

 ivium. 



The criterion for ascertaining its strength is the 

 quantity of the solution of gelatine which a given 

 quantity of it will precipitate. Isinglass is used 

 for this purpose, being entirely composed of ge- 

 latine. And Here it may be observed, that this is 

 the mode of ascertaining the quantity of tanning 

 principle in any vegetable substance, and, conse- 

 quently, how far they may be used as a substitute 

 for oak bark. 



The hides, after being prepared in the usual way, 

 are immersed for some hours in a weak tanning lix- 

 ivium of only one or two degrees ; to obtain which, 

 the latter portions of the infusions are set apart, or 

 else some of that which has been partly exhausted 

 by use in tanning. The hides are then to be put 

 into a stronger lixivium, where, in a few days, they 

 will be brought to the same degree of saturation 



