constituent Poits of astringent rcgetables. C15 



In examinins; the remainder of the infusions of catechu, 

 in which skin had been converted into leather, I found in 

 them much less extractive matter than I had reason to ex- 

 :pect, from the comparative analysis of equal portions of 

 .the unaltered infusions made by solutions of gelatine. At 

 iirst, I was inchned to suppose that the deliciency arose 

 from the action of the atmosphere upon the extractive mat- 

 ter, bv which a part of it was rendered insoluble. But, on 

 considering that there had been very little precipitation in 

 the process, I was led to adopt the supposition, that it had 

 <-nterfcd into union with the skin at the same time witli the 

 tannin ; and this supposition was confirmed by new expe- 

 riments. 



Both kinds of catechu arc almost wholly soUible in large 

 ouantities of water ; and, to form a complete solution, about 

 18 ounces of water, at 52°, arc required to 100 grains of 

 extract. The residuum seldom amounts to ^V^^ of the on- 

 |ii>al weight of the catechu ; and, in most cases, it is found 

 io consist chiefly of calcareous and aluminous earths, and 

 of fine sand, which, by accident or design, had probably 

 been mixed with the primitive infusion at the time of its 

 evaporation. 



A considerable portion of both kinds of catechu is soluble 

 in alcohol ; but, after the action of alcohol upon it, a sub- 

 fitance remains of a gelatinous appearance afid a light brown 

 colour, which is soluble in water, and is analogous in its 

 properties to gum or mucilage. 



The peculiar extractive matter in the catechu is much 

 less soluble in water than the tanning principle; and, when 

 ji small quantity of water is used to a large quantity of ca- 

 techu, the quantity of tannin taken up, as appears from the 

 nature of the strongest infusion, is very much greater than 

 that of the extractive matter. 



The extractive matter is much more soluble in warm^ 

 water than in cold water ; and, when saturated solutions of 

 catechu are made in boiling water, a considerable quantity 

 of extractive matter, in its pure state, falls down as the 

 li(|uor becomes cool. 



The peculiar e.vtractive matter of the catechu may be 

 likewise obtained by repeatedly lixiviating the catechu, when 

 in /ine powder, till the fluids obtained cease to precipitate 

 gelatme; the residual solid will then be found to be the 

 Bubstance in question, 



The pure extractive matter, wdielher procured from tlie 



Bombay or Bengal catechu, is pale, with a faint tinge of 



red brown. It has no peretptible smell j its taste is slightly 



4 a>tringcnt; 



