Caventou ofi the Chemical Properties of Starch. 313 



tlty of matter to the water. This solution is turned blue on the 

 addition of iodine, and in a few hours the ioduret of fecula falls 

 down. Hence, salep contamsjecula, but only in very minute pro- 

 portion. The jelly-like mass, remaining after the action of boil- 

 ing water, is of course insoluble in that fluid under any circum- 

 stances; it is very soluble in hydrochloric acid, and yields ox- 

 alic acid when treated with nitric acid. It is therefore the princi- 

 ple discovered by Bucholz, and known by the name of Bassorine. 

 This analysis shews that salep is not an amylaceous matter, but 

 is closely allied to gum tragacanth, which, according to Bucholz, 

 consists almost entirely of gum and bassorine. 



Sag-o when treated with successive portions of cold water, and 

 then with boiling water, is almost entirely dissolved, and appears 

 therefore to be homogeneous. Cold water takes up a large 

 quantity of it, and forms a transparent mucilaginous fluid, which 

 becomes intensely blue on the addition of iodine. As fecula, in 

 its characteristic state, is insoluble in water, and as no other sub- 

 stance strikes a blue colour with iodine, Caventou infers, that sago 

 is modified fecula, the modification consisting in the amylaceous 

 substance, (which, according to the process followed in the West 

 Indies for procuring it, must be insoluble in water, and therefore 

 true fecula), being converted by drying or roasting into amidine. 



Tapioca when treated with cold water, rapidly yields a por- 

 tion to it, and, after several successive macerations, it is entirely 

 dissolved, without the aid of heat. All these fluids of macera- 

 tion strike a strong blue colour with iodine. Tapioca, therefore, 

 is closely aUied in nature to sago, and, like it, is fecula modified 

 by roasting, or amidine. 



Arrow-root must be dried without heat ; for, like the fecula of 

 wheat and the potato, it is insoluble in cold water, with the ex- 

 ception of a mere trace of gummy matter, which it parts with ; 

 and it forms a paste when heated in water to near the boiling 

 point. 



Several remarks are added to this paper of Caventou, on the 

 opinions of another French experimenter, M. Raspail ; who be- 

 lieves he has discovered, by microscopical observations, that the 

 grains of fecula are composed of a membranous cyst filled with 

 gum. Caventou considers this notion to be visionary. — Annales 

 de Chimie et de Physique, Avril 1826. 



