LACTIC ACID. 



181 



point of the titration is not well marked. There is more justifi- 

 cation for calculating the acidity to litmus as lactic acid, as both 

 the salts of milk and carbonic acid are not appreciably acid to 

 litmus paper. 



The following figures obtained by the author on sour milks 

 will show the enormous difference in the two results ; the figures 

 have in both cases been calculated to lactic acid : 



Acidity (to phenol-phthalein), 1 *24 

 (to litmus paper), . 0-65 



II. 

 1-89 

 1-14 



III. 



1-82 

 1-28 



IV. 

 1-52 



0-86 



V. 

 1-32 

 0-56 



Fig. 26. Soxhlet-Henkel Acidimeter. 



There is no good method for the quantitative determination 

 of lactic acid ; the results of the titration with litmus give 

 approximate results. An approximation nearer to the truth 



N 

 may be made by distilling some of the milk into a little alkali, 



