ei4 Experiments and Observations on the 



After the mixture of the solution of carbonate of potash, 

 and the infusions had been exposed to the atmosphere for 

 some hours, a brown crust was found to have formed upon 

 its ftuvfacej and a shght precipiution had taken place. 



The salts of alumme precipitated the infusions, but less 

 copiously than they precipitate the infusion of galls. A 

 similar effect was produced by nitrate of potash, sulphate 

 of magnesia, prussiate of potash, and many other neutral 

 !=!alts. 



Tlie nitrate, or acetite, of lead, in concciitrated solution, 

 when poured into the infusion produced in it a dense light 

 brown precipitate, which gave to the fluid a gelatinous ap- 

 pearance. After this effect, there was no free acid found 

 jn it ; and both tb,e tannin and the extractive matter seemed 

 to have been carried down la union with a portion of the 

 metallic salt. 



The solution of mnrjate of tin acted upon the infusion of 

 catechu in a manner similar to that in which it acts upon 

 the infusion of galls. 



The least oxygenated sulphate of iron produced no 

 change in the infusion. With the most oxygenated sul- 

 phate it gave a dense black precipitate, which, when dif- 

 fused upon paper, appeared rather more inclined to olive 

 than the precipitate from galls. 



The infusions were pre.cipilatcd by the solution of al- 

 bumen. 



The precipitates by gelatine had all a pale tint of red 

 brown, which became deeper when they were exposed to 

 the air. The compound of gelatine and the tannin of the 

 strongest infusions of catechu appeared, by estimation of 

 the quantity ot isinglass in the solutions used for their pre- 

 cipitation, to consist of about 41 parts of tannin and 59 of 

 gelatine. 



Of two pieces of calf-skin which weighed, when diy, 

 132 grains each, and which had been prepared for taiming, 

 one was immersed in a large quantity of the infusion ot 

 catechu from ikngal, and the other in an equal portion ot 

 the iiifusion of that from Bombay. In less than a month 

 they were found converted into leather. When freed from 

 moisture, by long exposure in the sunshine, they were 

 weighed. The lirst piece had gained about 34 grains, and 

 the second pi.x-e 33J- grains. The leather was of a much 

 deeper colour than tiiat tanned with galls, and on the upper 

 surface was rec} browri. It was not acted on by hot or cold 

 jvater; and its apparent strength was the same as that ot 

 similar leather tamied in the usual manner. 



In 



