1826.] Alcohol derived from the Fermentation of Bread, 363 



Article IX. 



Alcohol derived from the Fermentation of Bread, 

 By Mr. Thomas Graham. 



(To the Editors of the Annals of Fhilosophy,) 



GENTLEMEN, Edinbur gh^ Sept. 2b^ \m6. 



Two facts of considerable importance in determining the 

 nature of the panary fermentation, have been made known by 

 your ingenious correspondent upon the art of baking bread. He 

 has shown that the fermentation depends upon the saccharine 

 ingredient of the flour, by renewing it when exhausted by the 

 addition of sugar ; and provided for the little alteration in the 

 proportion of sugar existing in the flour, before and after fer- 

 mentation, by exhibiting the influence of the baking in convert- 

 ing a portion of the starch into sugar. From the known laws of 

 the decomposition of sugar, it is presumed, with considerable 

 reason, that the fermentation is the vinous. The production of 

 alcohol in the course of the fermentation of bread in baking, 

 which we have found to take place, and rendered appreciable, is, 

 perhaps, a most irrefragable proof of which this theory is 

 susceptible. 



To avoid the use of yeast, which might introduce alcohol, a 

 small quantity of flour was kneaded, and allowed to ferment in 

 the usual way, to serve as leaven. By means of the leaven a 

 considerable quantity of flour was fermented ; and, when the 

 fermentation had arrived at the proper point, formed into a loaf. 

 The loaf was carefully inclosed in a distillatory apparatus, and 

 subjected for a considerable time to the baking temperature. 

 Upon examining the condensed liquid, the taste and smell of 

 alcohol were quite perceptible, and by repeatedly rectifying it 

 a small quantity of alcohol was obtained of strength sufficient to 

 burn, and to ignite gunpowder by its combustion. 



The experiment was frequently repeated, and in different 

 bakings the amount of alcohol obtained, of the above strength, 

 found to vary from 0'3 to 1 per cent, by weight of the flour 

 employed. When the fermented flour was allowed to sour 

 before baking, the amount of alcohol rapidly diminished ; and 

 in all cases, the disagreeable empyreuma completely disguised 

 the peculiar smell of the alcohol, when in its first diluted state, 

 and in vapour. I am, Gentlemen, with great respect, 



Your most obedient servant, 



Thomas Graham. 



