LACTIC ACID. 93 



juice from dogs, found no lactic acid, and ascribed the acid reaction of 

 the fluid to acid phosphate of lime, while Lassaigne,* in opposition 

 to this view, attempted to prove the presence of free hydrochloric 

 acid. Subsequently, experiments have been instituted by Bernard 

 and Barreswil,f Pelouze,{ and Thomson, which have led all these 

 chemists to believe that they have proved the existence of lactic 

 acid in pure gastric juice. Very recently 1 1| prepared the lactates 

 from a larger amount of pure gastric juice than had hitherto been 

 employed, and obtained them in such quantities that I was enabled 

 to make an ultimate analysis of several of them, and to determine 

 the atomic weight, which proved that the acid of the gastric juice is 

 perfectly identical with lactic acid. I found that pure gastric juice, 

 even on mere evaporation in vacuo, undoubtedly developes hydro- 

 chloric acid (in one case it amounted to 0'125), but that there is 

 then always an acid residue left, which, besides free lactic acid, 

 contains lactate of lime and alkaline chlorides ; whence we may 

 conclude that there are in the gastric juice both free lactic acid and 

 lactates, in addition to free hydrochloric acid. 



According to my observations, chloride of calcium, but not 

 chloride of sodium, (as Bernard and Barreswil maintain,) is decom- 

 posed during evaporation with free lactic acid, even in vacuo ; hence 

 it is not surprising that pure gastric juice should develope vapours 

 in vacuo, which, when passed into a solution of nitrate of silver, 

 should form chloride of silver. I must further remark, that 

 the lactates obtained from the pure gastric juice, as well as from the 

 contents of the stomach, had not the composition of the a lactic 

 acid, but that of the b lactic acid obtained from sugar. Bernard 

 and Barreswil allege, in opposition to Prout's opinion, that pure 

 gastric juice is rendered decidedly turbid by a drop of a dilute 

 solution of oxalic acid, while an equal quantity of oxalic acid in a 

 solution of lime containing only rs^th part of free hydrochloric 

 acid, causes no precipitate. Further, starch, when boiled with 

 hydrochloric acid, loses its property of being coloured blue by 

 iodine, while lactic acid does not induce this change. On boiling 

 a solution of a lactate with a little hydrochloric acid and starch, the 

 properties of the last-named body remain unaffected : starch boiled 

 with gastric juice retains the property of being coloured blue by iodine. 



* Journ. de Chim. med. T. 10, p. 73 et 189. 



f Journ de Pharm. et de Chim. Janv. 1835. p. 49. 



% Compt. rend. T. 19, p. 1227. 



Philos. Mag. 3rd series. Vol. 26, p. 420. 



|| Berichte d. Gesellschaft d. Wiss. zu Leipz. Bd. 1, S. 100-105. 



