286 M. Caventou's Chemical Researches on Starch, 



produce this compound. This is so true, that if starch is boiled 

 for a long while in water, care being taken to renew the latter 

 as it evaporates, in the manner Vogel has done, we finish 

 by obtaining by means of evaporation, instead of empois, a 

 hard, horny, transparent matter, which dissolves in cold wa- 

 ter, and in which no sensible traces of pure starch are to be 

 found. It is easy to conclude, from what precedes, that in 

 this long ebullition the water has had time to react upon the 

 whole mass of starch, and to modify even the last particles of 

 it. 



This starch, thus modified, has already been perceived by 

 chemists, but it has never been made the object of a particular 

 study; they have always been contented with saying, that 

 starch, after having been dissolved in boiling water, partly re- 

 dissolved in cold water. 



It is only of late that M. de Saussure has designated it spe- 

 cifically by the name of amidine, considering it as a product 

 of the spontaneous decomposition of the empois. 



I do not, however, believe, that the origin of amidine is es- 

 sentially the result of a spontaneous decomposition. I am per- 

 suaded, on the contrary, that this sort of putridity of empois 

 is quite foreign to the production of this substance ; and it is 

 sufficient to cast a glance on the process by which M. de 

 Saussure extracts amidine, in order to be convinced of it. In 

 fact, this philosopher obtains amidine by boiling the residue 

 insoluble in cold water, of empois decomposed by time ; filter- 

 ing the liquors after cooling, and bringing these near to dry- 

 ness, he obtains a fragile, yellow, and half transparent matter, 

 which is amidine. If now we recollect the nature of empois, 

 such as we have just considered it, is it not evident that its 

 insoluble residue left to grow sour must be, for the greater 

 part, formed of pure starch, which, by its state of aggregation, 

 must have been the last principle liable to be attacked by pu- 

 tridity ? Is it not also evident, that by treating this amyla- 

 ceous residue by boiling water, M. de Saussure has modified, 

 by this very act, the nature of this starch, and has converted 

 it into amidine? I am so much the more induced to believe 

 it, as this amidine has all the characters of our modified starch ; 

 it becomes blue by iodine, precipitates infusion of galls, &c. 

 Thus, according to my view, M. de Saussure, far from having 

 extracted amidine, will have formed it himself; and he will 

 thus have misunderstood this truth, of which he does not 

 speak in his Memoir, " that in the ordinary processes of our 

 laboratories we form, and often change, the nature of the 

 bodies which we wish to study." 



We have just seen that the essential characters of amidine 



are, 



