suhsiances found in Guiana. 241 



The tree is not described ; but it bears a large apple con- 

 taining several oblong seeds, and it appears to belong to the 

 family Sapotacece. 



The ducali is a substance, differing from all others, perhaps, 

 with which naturalists and chemists are acquainted. It is 

 milk white and thick as new cream. Its taste is slightly bit- 

 ter and sourish. It is diffusible and miscible in water cold 

 and hot, and remains unchanged thereby. 



On mixture with spirit (proof 18), it instantly forms a solid 

 elastic mass, strong like cahuchi, but growing brittle on drying, 

 or even though remaining in the liquid. This cake is white, 

 and half the bulk of the milk used. Beside the cake there is 

 a white curdy loose precipitate which falls from the liquor. 



The milk is not changed or at all acted on by the mineral 

 or vegetable acids that I have tried, viz. the nitric, sul- 

 phuric, oxymuriatic, or acetic, though both strong and dilut- 

 ed, were tried. No change takes place with carbonate of po- 

 tass, lime-water, or oxymuriate of mercury. 



The only two substances yet found to affect it are the ace- 

 tate of lead and the nitrate of silver. The latter throws down 

 a reddish precipitate ; the former, a copious white, half curdy 

 precipitate. The supernatant liquor filtered is not affected 

 by alcohol ; but, inversely, the filtered spirituous tincture let» 

 fall a blue feculent precipitate on adding the acetate of lead. 

 It is evident that the acetate of lead unites with both the cake 

 and the loose precipitate, and even with that part held in so- 

 lution by the alcohol or by the watery part of the spirit, which 

 now sinks.* 



The cake or coagulum appears to me a singular substance. 

 It is not soluble in any proportion in water or alcohol, nor in 

 the strong mineral or vegetable alkalies. It has all the ap- 

 pearance of a resin, soft and adhesive while moist; when dried, 



* The articles expected to unite or precipitate each other should not be 

 too much diluted. If much diluted with water, they require a proportion- 

 ally longer time, perhaps may scarcely act at all. I find the best method 

 is to put them together strong, i. e. both well concentrated, and afterwards 

 dilute the mixture. In this way, the experiment will always succeed, if 

 they are substances which mutually act on each other. They must be 

 strong, m order effectually to act on each other, and diluted to show their 

 action, especially if viscid. 



NEW SERIES. VOL. I. NO. II. OCT. 1829. Q 



