PROCEEDIMS OF THE POLYTECHNIC ASSOCIATION. 481 



Notwithstanding parliamentary and municipal acts, which, in 

 Paris, for a second offence, deprives the baker of his license, it is 

 still frequently found in the cheaper forms of bread. Its effect is 

 to stiffen the gluten, which has been impaired by growing, sweat- 

 infiT, heatinjr or sourina: — and so i3roduce a factitious whiter and 

 more poi*ous loaf than would be possible with the poor flour in 

 the ordinary process of making bread. 



Among the deleterious qualities when swallowed with food, 

 ascribed to alum, Leibig mentions its withdrawal of phosphoric 

 iacid, forming a phosphate of alumina — and so rendering useless a 

 certain amount of an important agent of nutrition, 



Orphea and Mitschertich observed its deleterious effects on ani- 

 jnal life. Fatal effects upon human life have been noticed in Eng- 

 land and in this country. A physician of New York recently losfc 

 a child from the accidental use of alum, when borax had been pre- 

 scribed. 



It has been suggested that if alum was mixed with flour and 

 alkali enough to neutralize the sulphuric acid added, it would 

 yield a neutral prescription which woukl become an inert powder. 

 In order that this might be true, alumina must be insoluble in the 

 gestric juice which is an acid fluid. 



The acid reaction was early ascribed by Prout to free hydro- 

 chloric acid. He had found that by evaporation of the gastric 

 juice to dryness, and subjecting the residue to the distillation, he 

 obtained in the distillation, an acid which gave a precipitate with 

 nitrate of silver, soluble in ammonia, and insoluble in nitric acid; 

 and concluded that the acid reaction was due to hydrochloric acid. 



Later observei*s, finding lactic acid present in the gastric juice, 

 gave a juster interpretation to the phenomenon. Lactic acid being 

 non-volatile, while hydrochloric acid is volatile, would, in the 

 presence of chlorkles, upon evaporation and distillation, drive out 

 hydrochloric acid, leaving lactates in the place of the chlorides. 

 The discovery of traces or other organic acids led to the opinion 

 that they might share in the cause of the acid reaction. 



More recent observers, recogniging the presence of acid phos- 

 phate of lime in the gastric juice, attributed to this body the acid 

 reaction. This body would, of course, be present where phos- 

 phates and lactic acid, or other organic acids come together, and 

 would yield the reaction observed by Prout. 



The acid phospha.tes of lime, on the application of heat, would 



[Am. Inst.J EE 



