284' M. Caventou's Chemical Researches on Starch, 



forget the results of these first experiments, when very re- 

 cently M. Edwards showed me a memoir on fecula, published 

 by M. Raspail, and inserted in a number (for December 

 1825) of the Annals of Natural Sciences. I must own that 

 the reading of this memoir interested me strongly, by the cu- 

 rious facts which it contains : but as I have observed some 

 which the author has not mentioned, and as we morever dif- 

 fer in the manner of explaining the phaenomena, 1 thought 

 that perhaps it would not be useless to publish my investiga- 

 tions, incomplete as they are. 



Action of Water on Starch. 



I must premise, in detailing my experiments, that I have 

 always conducted them, and considered the phaenomena, under 

 the persuasion that fecula is an immediate, pure, and homoge- 

 neous principle. This consideration it seems to me to be im- 

 portant to remark. 



It is well known that cold water has no sensible action on 

 starch ; but that when this fluid is elevated to a temperature 

 of from 140° to 160° Fahr., it dissolves this principle, and 

 forms a transparent gelatinous mass, which is generally 

 known by the name of empois. What then is empois ? It 

 is, we have long been told, the solution or combination of 

 starch with a certain quantity of water ; it is in fact a hydrate 

 of starch. Such is, I believe, the opinion given in all the 

 books on the subject of the nature of empois. Nevertheless, if 

 we well consider the properties of this preparation, it is easy 

 to convince ourselves that it evidently differs from starch ; or 

 rather that the starch has lost, in this supposed combination, 

 its most characteristic property; that is to say, its insolubility 

 in cold water. In fact, when we have transformed starch into 

 empois, it is impossible to obtain this latter such as it was be- 

 fore the experiment ; it redissolves in a greater or less degree 

 in cold water, a property which pure starch has not. This 

 result seems then to prove that this principle changes its na- 

 ture, in its conversion into empois, by the action of boiling 

 water, and that the latter is not a simple hydrate. 



Of the Empois of Starch. 



I distinguish two kinds of empois : 1st, that at the minimum 

 of starch, which is quite transparent or very slightly opa- 

 lescent ; and 2dly, that at the maximum of starch, which is 

 nearly or quite opaque. 



The first, well cooled, becomes diluted and dissolved in a 

 great quantity of cold water ; it only leaves undissolved a small 

 white residue, which is starch ; the filtered liquor is limpid 



and 



