LACTIC ACID. 87 



the form of white hard bodies, which under the microscope are seen 

 crystallising in tufts of delicate needles, each two of which are so 

 placed in relation to the other, that collectively they resemble 

 overlapping tufts or pencils : their form is tolerably charac- 

 teristic, and they cannot be confounded with other organic 

 lime-salts, as for instance, the butyrate. Lactate of lime loses all 

 its water at 100, and is soluble in almost every proportion in 

 boiling water and in alcohol ; the salt of the a lactic acid dissolves, 

 however, in 12'4 parts of water, and that of the b lactic acid in 

 9-5 parts ; both salts may be heated to 180 without decomposi- 

 tion. 



A crystallographic investigation shows that the b lactates of 

 magnesia, of protoxide of manganese (which is colourless or of a 

 pale amethystine tint,) of protoxide of iron (which is of a pale 

 yellow colour), of cobalt (which is of a peach-colour), of nickel, 

 and of zinc, are isomorphous, since with three atoms of water of 

 crystallisation, they form vertical prisms with horizontal terminal 

 surfaces, or with superimposed obtuse horizontal prisms. 



Lactate of magnesia. The salt of a lactic acid contains 4 atoms 

 of water of crystallisation, and is somewhat more soluble in spirit 

 than that of b lactic acid. 



Lactate of nickel is of an apple-green tint, and is difficult of 

 solution in cold water and in spirit ; the salt of a lactic acid loses 

 all three of its atoms of water at 100, while that of b lactic acid 

 does not part with its third atom at a lower temperature than 130. 



Lactate of zinc. The a lactate of zinc contains only 2 atoms of 

 water of crystallisation, which it very slowly loses at a temperature 

 of 100; it begins to decompose at 150, is soluble in 5'7 parts of 

 cold and 2'88 of hot water, and in 2' 23 parts of alcohol ; the b 

 lactate loses its water of crystallisation very rapidly at 100, 

 bears exposure to a temperature of 210 without decomposition, 

 and dissolves in 58 parts of cold and 6 of boiling water, but is 

 almost insoluble in alcohol. C. Schmidt,* who is the only observer 

 who has devoted great attention to the forms of microscopic crystals 

 with the object of diagnosing such bodies in the animal fluids, gives 

 a very accurate description and figure of the form of lactate of 

 zinc; he mentions the club-like shape of the crystals during their 

 process of formation, and their curved surfaces, as especially cha- 

 racteristic of this salt. 



Lactate of cadmium crystallises in anhydrous needles, and is 

 almost insoluble in alcohol. 



* Entwurf e. allg. Untersuchungsmeth. der Safte u. Excr, 1846, S. 78 ff. 



