ON VEGETABLE MUCILAGES. 33 



differed from it in soon showing a tendency to putridity. Their muci- 

 wben it exhaled a very nauseous odour. The reagents used pufreStion!* 

 in the former experiments were employed in this case. The Xfsted with 

 acetate of lead formed a dense precipitate, composed of the reagents, 

 white fdms and flakes; the super-acetate of lead threw 

 down a precipitate in moderate quantity ; the nitrate of mer- 

 cury a precipitate of a light pink colour ; the nitro-muriate 

 of tin a copious white precipitate ; the nitro-muriate of gold 

 u liglit brown precipitate ; the oxysiilphate of iron a brown ^'R* 



precipitate; the infusion of galls also formed a precipitate; 

 while the silicated potash produced no effect *. 



After having- examined the properties of six species of Experiments 

 mucilage, I next turned my attention to some bodies, which sub^tancfs*"^ 

 although obviously different from the mucilages, yet seem 

 to have a close connection with them in their origin and con-- 

 stitution. The first of these is starch. A quantity of it Starch, 

 was boiled in water, until it had acquired that state of half 

 solution, of which it is alone capable, and in this form it 

 was subjected to the usual trials. With the acetate of lead 

 an immediate and very dense precipitate was thrown down, 

 aiid so intimate a combination formed between the lead and 

 the starch, that the water was separated from them nearly in 

 a limpid state. By the nitro-muriate of tin a very copious 

 precipitate was also thrown down, although less dense than * 



tJie former; but no effect appeared to be produced by any 

 other of the reagents. It is not without considerable diffi- Effects of infu- 



dence, that 1 venture to dissent from the opinion of Dr. f^o" ^^ t^»i o^- 

 rr.1 1 1 • p 1 • mg to the wa- 



Ihomson, on tlie subject ot the action which takes place ter. 



between tan and starch. When equal quantities of the mu- 

 cilage of starch and the infusion of tan are mixed together, 

 a precipitate is produced, which slowly subsides ; it disap- 

 pears by heating the fluid, and again becomes visible as it 

 cools. This process is described as a characteristic property 

 of tan ; but 1 have observed the same appearance to ensue, 

 if an equal quantity of water be added to the starch muci- 

 lage, it appears to depend merely upon the insolubility of 

 starch in cold water. 



The effects produced by the reagents upon paste, made Flour past«. 



* These results differ from those of le Roiix. Ann. Chira. 145 S: seq. 

 Vol. XVIII—Sept. 180(t. D by 



