LACTIC ACID. 89 



crystals solidify on cooling, into a crystalline mass which is devoid 

 of odour, has a slightly acid taste, and dissolves slowly in water; its 

 conversion into lactic acid is more rapid than that of the so-called 

 anhydrous lactic acid. 



Lactone, C 10 H 8 O 4 (produced according to the formula 

 2C 6 H 5 O 5 .HO [2CO 2 + 4HO] = C 10 H 8 O 4 ) is obtained on dis- 

 tilling anew the fluid products of distillation of lactic acid, washing 

 the distillate with water, and drying the insoluble portion with 

 chloride of calcium ; the pure lactone is a colourless fluid with an 

 aromatic odour and a burning taste, which boils at 92, and when 

 inflamed, burns with a blue tint. 



Lactamide, C 6 H 7 NO 4 ==H 2 N.C 6 H 5 O 4 , is formed from lactide 

 and dry ammoniacal gas : it crystallises in colourless, right rectan- 

 gular prisms, and is decomposed into ammonia and lactic acid. 

 This body is moreover isomeric with the powerful base, sarcosine, 

 discovered by Liebig, and with the longer-known indifferent sub- 

 stance, urethran. 



Preparation. Lactic acid is very often formed during the fer- 

 mentation of fluids containing sugar or starch, and it might as well 

 be maintained that there is a specific lactic fermentation, as that 

 there is a distant acetic or butyric fermentation. Hence lactic acid 

 is not only found in milk which is turned sour, but also in the acid 

 waters of starch fabrics, in Sauer-kraut, in sour cucumbers, in fer- 

 mented beet-root juice, &c. (The conditions under which this con- 

 version takes place are explained in a future part of this work under 

 the head of " fermentation of milk/ 5 ) 



The best method of obtaining lactic acid is by exposing sugar 

 to this kind of fermentation, under the combined influence of milk 

 and cheese. 



Bensch* has employed the following practical method of ob- 

 taining it : 6 parts of cane-sugar, T V tn P art f tartaric acid, 8 parts 

 of sour milk, J part of old cheese, and 3 parts of levigated chalk, are 

 mixed with 26 parts of water, and exposed to a temperature of 32. 

 In the course of eight or ten days a semi-solid magma of lactate of 

 lime is formed ; on boiling it with 20 parts of water and ^h P art 

 of caustic lime, filtering it at a boiling temperature, and slightly 

 evaporating it, the lactate of lime separates in a few days in gra- 

 nules. The salt must be drained and pressed, again dissolved in 

 twice its weight of water, decomposed with -/-% parts of sulphuric 

 acid, the precipitated gypsum removed by filtration, and the acid 

 fluid saturated with T % of carbonate of zinc. The crystallised zinc- 

 * Ann. d. Ch. u, Pharm. Bd. 61, S. 174-176. 



