10 ANIMAL ACIDS DESTITUTE OF AZOTE. 



suitable to the English language. The French chemists endea- 

 voured to prove that lactic acid is merely the acetic, holding some 

 animal matter in solution. But this opinion was refuted by 

 Berzelius. It was afterwards observed that lactic acid is formed 

 when various vegetable substances are allowed to get sour, parti- 

 cularly when oatmeal is left in a considerable quantity of water. 



The constitution and properties of lactic acid were fully inves- 

 tigated by MM. Jules Gay-Lussac and Pelouze. A full account 

 of the facts which they ascertained has been given in the Che- 

 mistry of Vegetable Bodies, (p. 22). The reader is therefore re- 

 ferred to that work. It has been shown by these chemists that 

 the atomic weight of lactic acid is 9, and that its constitution is 

 C 6 H 4 O 9 . 



MM. Fremy and Boutron-Charlard have ascertained that 

 all animal substances which act as ordinary ferments have the 

 property of gradually converting sugar, dextrin, gums, starch, 

 &c. into lactic acid. The process is stopped by a heat of 212*. 

 Their observations have led them to the following method of 

 preparing lactic acid : Put malt, slightly moistened, for a few 

 days into a stoppered bottle. The animal matter contained in 

 the malt undergoes a modification ; the temperature rises, and 

 if we keep this modified malt for two or three days in water of 

 the temperature of 104, that water becomes strongly acid, and 

 contains a notable quantity of lactic acid. * 



They have found that animal membranes (bladder for example) 

 after being dried and kept in moist air till it begins to undergo 

 decomposition, has the property of converting a solution of sugar 

 into lactic acid. When milk becomes sour lactic acid is gene- 

 rated by the .action of the casein on the sugar of milk. The 

 casein combines with lactic acid, and becomes insoluble, which 

 stops the process. But if we saturate the lactic acid formed with 

 bicarbonate of soda, the casein becomes again soluble, and act- 

 ing on the sugar of milk a new portion of lactic acid is formed. 

 This process of neutralization may be repeated till the whole 

 sugar of milk is converted into lactic acid, f 



MM. Cap and Henry have discovered that the urea in urine 

 is in the state of lactate of urea. They have made some obser- 

 vations on the lactates which deserve to be stated J 



* Jour, de Pharm. xxvi. 477. f Ibid, xxvii. 325. 



j Ibid. xxv. 133. 



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