fcXPERtMENTS ON ASTRINGENT VEGETABLES. 273 



The folution of muriate of tin, acted upon the infufion of Muriate of tin, 

 Catechu in a manner fimilar to that in which it acts upon the 

 infufion of galls. 



The leaft oxygenated fulphate of iron produced no change in Sulphates of 

 the infufion. With the moft oxygenated fulphate it gave a denfe 

 black precipitate, which, when difTufed upon paper, appeared 

 rather more inclined to olive than the precipitate from galls. 



The infufions were precipitated by the folution Of albumen. 



The precipitates by gelatine had all a pale tint of red-brown, Precipitates from 

 which became deeper when they were expofed to the air. The JjJ^^ 1 efaiine" 

 compound of gelatine and the tannin of the ftrongeft infufions 41 tannin and 

 of catechu appeared, by eftimation of the quantity of ifinglafs $9 6 e l atine » 

 in thefolutions ufed for their precipitation, to confifl of about 

 41 parts of tannin, and 59 of gelatine. 



Of two pieces of calf-fkin which weighed, when dry, 1 32 Calf /kin (quick- 

 grains each, and which had been prepared for tanning, one was W tanned by 



1. r j • 1 L - L c ^ ■ c r c L 1 r «techu afforded 



immerled in a large quantity of the infufion or catechu from good leather. 

 Bengal, and the other in an equal portion of the infufion of Th . e increafeof 

 that from Bombay. In lefs than a month they were found con- tner left than 

 verted into leather. When freed from moifture, by long ex- one fifth of the 

 pofure in the funlhine, they were weighed. The firft piece ea er * 

 had gained about 34- grains ; and the fecond piece 35f grains. 

 The leather was of a much deeper colour than that tanned 

 with galls, and on the upper furface was red-brown. It was 

 not acted on by hot or cold water; and its apparent ftrength 

 was the fame as that of fimilar leather tanned in theufual man- 

 ner. 



In examining the remainder of the infufions of catechu, in Little extractive 

 which Ikin had been converted into leather, I found in them matt 

 much lefs extractive matter than I had reafon to expect, from 

 the comparative analyfis of equal portions of the unaltered in- 

 fufions made by folutionsof gelatine. At firft, I was inclined 

 to fuppofe that the deficiency arofe from the action of the aU 

 mofphere upon the extractive matter, by which a part of it 

 was rendered infoluble. But, on confidering that there had 

 been very little precipitation in the procefs, I was led to adopt It had in part 



the fuppofition, that it had entered into union with the (kin, at ^mVintA with 



. . r r . the fkin. 



the fame time with the tannin ; and this fuppofition was con- 

 firmed by new experiments. 



Bolh kinds of catechu are almofr. wholly foluble in large Water diflblves 

 quantities of water ; and, to form a complete folution, about 18 ""^hu^ 01 * 



Vol. V. — August. T ounces 



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