Chemical Science. 377 



" D. Taddei, my companion in Natural Philosophy, having 

 undertaken researches in fermentation, and particularly in that 

 of grain and pulse, in various cases has ascertained that the 

 gluten of wheat is composed of two substances, perfectly dis- 

 tinct from each other, one of which he has named gloiodina, 

 and the other zimoma. The first of these gives to gluten its 

 elasticity ; and the second is the cause of the fermentation 

 which takes place in the mixtures of gluten with other vegetable 

 substances. D. Taddei had occasion to mix various gums, 

 gum resins, and resins, with the different kinds of flour. 

 Amongst the mixtures it was found, that that of the powder of 

 the resin of guaiacum with wheat flour, became of a very fine 

 blue, as soon as it was well kneaded with water, in contact 

 with the air. Various colours were produced with the flour of 

 other kinds of grain ; and it appeared, that the shade of blue 

 colour, produced by the various mixtures, corresponded to the 

 quantity of zimoma contained in them. D. Taddei has made 

 me acquainted with these facts, and whilst he has been engaged 

 on other things, I have pursued them somewhat farther. I 

 have observed that guaiacum does not give any blue colour 

 to pure starch, however mixed with it, nor to any other ve- 

 getable substance, not containing zimoma ; that it is not at 

 all, or very slightly, tinged by flour poor in gluten, and that 

 it is not tinged by that in which the gluten has been much al- 

 tered. But when guaicum is mixed with pure gluten, or pure 

 zimoma, the colour instantly appears, and is a most superb blue. 

 Guaiacum does not, however, become at all coloured by mix- 

 ture with zimoma, unless contact with the oxygen of the air 

 be allowed. 



The powder of guaiacum is, therefore, a re-agent, capable 

 of discovering the alteration which flour may have undergone 

 by fermentation in magazines, ships, §-c. ; and also of ascer- 

 taining if it be mixed with the flour of other seeds defi- 

 cient in gluten. It will also test the purity of starch. The 

 flour of grain is consequently too a test of the purity of the 

 resin guaiacum, which in commerce is almost always adulterated 

 and falsilicd. — Giornalc di Finica, I. p. 168. 



