810 LACTIC AND VISCOUS FERMENTATIONS. 



taken up by alcohol at 100, which dissolves the lacfate of soda. 

 Sulphuric acid added in proper quantity to the alcoholic solution, 

 forms sulphate of soda, which precipitates, and the liquid yields 

 by evaporation lactic acid nearly pure. To purify the acid, it 

 may be converted into lactate of lime, which crystallizes imme- 

 diately in tufts which are perfectly white. From this salt 

 lactic acid may be again separated by means of sulphuric acid. 

 Or, the original lactic acid may be saturated with any other 

 base, and crystallized lactates obtained in a very short time. 



Concentrated to a maximum by evaporation, lactic acid is a 

 thick, colourless, uncrystallizable liquid, of density 1.215, with- 

 out smell, and having a strong sour taste, which is scarcely 

 sensible when the acid is dilute. It is soluble in water and 

 alcohol. Lactic acid dissolves the phosphate of lime, a property 

 which some acids, particularly the acetic, do not possess ; it 

 coagulates milk when warmed. When heated to 482 (250 

 cent.), it undergoes a decomposition, water and several other 

 secondary products appearing, but the principal product being 

 a white crystalline sublimate, of which the composition is 

 C 6 H 4 O 4 ; that is, anhydrous lactic acid minus 1 atom of 

 water. 



This new acid may be purified by dissolving the sublimate in 

 boiling alcohol, from which it precipitates on cooling, in the 

 form of rhomboidal tables, of a brilliant whiteness, which have 

 a weak sour taste, are fusible at 224.6 (107 cent.), and sublime 

 at 482 without alteration. These crystals are very slowly 

 soluble in cold water, but dissolve easily in boiling water; the 

 acid then assumes 2 atoms of water and returns to the condition 

 of hydrated lactic acid. 



In the lactates, the .single atom of basic water only of the for- 

 mula is replaced by a metallic oxide ; no acid lactates are known, 

 but some basic salts of zinc and the magnesian metals appear to 

 exist, which have not been studied. They are all soluble in 

 water; lactate of zinc is the most sparingly soluble. 



Lactates. No lactate of oxide of ethyl has been formed. 

 The lactates of potash, soda and ammonia are deliquescent, and 

 do not affect a regular form. The lactate of barytes is similar. 

 Lactate of lime exists to the extent of 2 or 3 per cent in nux 

 vomica. It crystallizes in colourless needles radiating from a 

 centre, which contain 5 atoms of water of crystallization. Lac- 

 tate of zinc is crystallized by the cooling of a boiling solution, 



