34 THE SOLUBLE CONSTITUENTS. 



Their constitution is given by E. Fischer as 



Glucose. Galactose. 



COH COH 



H-C OH H C OH 



OH-C H OH-C H 



H C-OH OH-C-H 



H C-OH H-C OH 



CH 2 OH CH 2 OH 



Wohl and List have confirmed the constitution of galactose. 



They are thus isomeric sugars differing only in the third 

 asymmetric carbon atom from the aldehyde group. 



It is not known whether these sugars on solution in water 

 give a constant rotation for a short time as in the case of milk- 

 sugar. Their specific rotatory powers [a] D are 



Glucose. Galactose. 



Equilibrium form, - - - 52'7 80'3 



a-inodification, - - 105 120 



Bi-rotation ratio, ... 2 1 '5 



Both sugars give, on treatment with phenylhydrazine acetate, 

 nearly insoluble osazones. Phenylglucosazone crystallises from 

 dilute alcohol in fine yellow needles melting at 211 C. when pure 

 to a dark red liquid ; phenylgalactosazone is obtained in yellow 

 needles from alcoholic solutions, which melt at 188 to 191 C. 

 with decomposition. Both are converted into osones by treat- 

 ment with strong cold hydrochloric acid. 



Products derived from Milk-Sugar. The most important of 

 these products is formed by the action of certain micro-organisms 

 on milk-sugar during the so-called lactic fermentation. By their 

 action the milk-sugar is split up into lactic or oxypropionic acid 

 almost quantitatively, a certain portion, however, being con- 

 verted into other products, of which carbon dioxide is the most 

 important. The micro-organisms which produce lactic acid are 

 acted on inimically by acids, so that not much more than 1 per 

 cent, of lactic acid is usually formed, unless the solution be kept 

 neutralised by chalk or other means. 

 H 



Its formula is CH 3 C COOH, and it contains an asymmetric 



ok 



carbon atom ; it is not, however, optically active, though the 

 isomeric sarcolactic acid possesses this property. It appears to 

 be a racemic compound ; but both the dextro- and Isevo -acids 



