292 M. Caventou's Chemical Researches on Starch, SfC. 



been made with a paper twice doubled. Should we like 

 better to suppose that a gummy matter has facilitated the so- 

 lution of a little starch, as it did with the phosphate of lime in 

 the salep? I shall then ask why this phenomenon was not 

 manifested by the salep itself. Besides, artificial mixtures 

 of great quantities of gum, either tragacanth or arabic, and of 

 a very little starch, put to steep in water and filtered at the 

 end of twenty-four hours, give a liquor purely gummy, and 

 in which iodine does not indicate the smallest trace of starch. 

 We must then necessarily conclude that sago is formed of a 

 variety of starch quite peculiar, which may be characterized 

 by its solubility in cold water, and distinguished from gum by 

 the action of iodine. 



Sago, submitted for the first time to the action of cold 

 water by macerating for four-and-twenty hours, swelled con- 

 siderably and remained at the bottom of the liquid ; treated 

 a second and a third time and many times repeatedly by 

 water at the same temperature, this fluid always dissolved 

 sensible quantities of it, which presented the same phaenomena 

 as at the first time. Submitted at last to the action of boil- 

 ing water, the sago totally dissolved, with the exception of a 

 few filaments ; and the solution presented the same characters 

 as that made in the cold, only they were more marked. These 

 results indicate, then, that sago is homogeneous in its compo- 

 sition, and that this consists simply in a variety of starch 

 soluble in the cold, and more soluble by heat. 



Of Tapioca. 



After sago, tapioca naturally succeeds, a sort of fecula, 

 very white, in irregular grains, and which is regarded as the 

 fecula of manioc, freed from the acrid substance which accom- 

 panies it by means of numerous washings in cold water, and a 

 slight tor refaction on iron plates. 



This substance treated with cold water, swells and partly 

 dissolves; the liquor filtered presents all the characters of that 

 obtained from sago. The often repeated washings always 

 produced liquors which became blue by iodine, and they may 

 be thus continued until the substance is totally dissolved. It 

 is useless to leave the water a long time in contact with the 

 tapioca to obtain the liquor of which we are speaking, for a 

 few seconds suffice. These phaenomena indicate then a very 

 great chemical analogy, I would even say identity, between 

 sago and tapioca ; and physicians might, it seems to me, sub- 

 stitute the one for the other without inconvenience. 



Now if I were asked whether any starch, properly so called, 

 exists in sago and tapioca, I would reply No: 1st, because these 



two 



