244 * N VEGETABLE ASTIUNSENTS. 



completely redissolved, and the second infusion ia rather 

 The transpa- lighter coloured than the former one. The transparent so- 



SJJrtSS, ,utious of catechu ' wlietnf;r foimed b y wann or b y <&\4 



part of their water, slowly deposit a part of their contents, in the form 

 contents, of the whitish residuum mentioned' above, while Rt the same 



time a kind of efflorescence creeps np along the sides of 

 the glass to some distance above the surface of the fluid. 

 This deposition proceeds the more rapidly, the stronger is 

 the infusion; but there does not appear to be any absolute 

 limit to its continuance. In one instance I found, that a 

 saturated solution of catechu, after standing two months, 

 and grow had lost rather more than half of its solid contents, but a 



mouldy. p &r £ Q jp j t j jac j b eeu expended in forming a stratum of mouldy 



The substance that has been deposited is less soluble in wa- 

 ter than the recent catechu, but it dissolves readily by an 

 increase of temperature; it forms a solution of a lighter 

 colour,. and it has less disposition to separate from the fluid. 

 Requires sue- Although catechu is so readily soluble in water, yet, as is 

 cessiveinfu- the case with galls, it requires a number of successive in- 

 fusions to separate the soluble part from the small insoluble 

 residue. Ten grains of catechu were infused in 50 times 

 their weight of water for 24 hours; the fluid was then 

 drawn off, and the same quantity of water was poured upon, 

 the residue. After 9 °f these successive infusions, the ef- 

 fect of the oxirnuriiite of tin was no longer visible, that of 

 jelly was barely so, but the oxisulphate of iron continued 

 to tinge the fluid until the 15th infusion, and at this period 

 the acetate of lead produced a very slight cloud. The in- 

 soluble residue left was not more than ^V of the weight of 

 the catechu employed; it seemed to be a heterogeneous 

 mass, consisting probably of accidental impurities, and it 

 may be expected therefore to vary in quantity r Mr. Davy 

 found no less than T V of the catechu upon which he operated 1 

 to consist of insoluble matter*. 

 Treated with Alcohol, at the temperature of the atmosphere, slowly 

 alcohol. dissolves catechu. By boiling the effect is much promoted, 



and the alcohol takes up about . Z V of its weight, which re- 

 mains permanently dissolved, but the quantity varies very 



* Phil. Trans. 130.3, p. 259. 



much 



