BY H. G. CHAPMAN. 439 



indicator. It has been found that, when 1 c.c. of a O'l % alcoholic 

 solution of phenolphthalein has been present in 100 c.c. liquid, it 

 has been easy to determine the first appearance of the pink 

 colour. The figures obtained have been found to vary with the 

 method of titration adopted. After much experiment the 

 following method has been adopted, and this has been used for 

 all titrations. 



25 c.c. milk have been added to a beaker which has contained 

 100 c.c. distilled water (free from C0 2 ) and 1 c.c. phenolphthalein 

 solution. ~q soda has then been run in until the first pink colour 

 has been observed. 



When the method is varied; different results have been obtained. 

 Thus with the same milk the following results have been found : 



25 c.c. milk plus 1 c.c. phenolphthalein, at 17° C, required 4 -2 c.c. ^o NaOH. 

 25 c.c. milk plus 1 c.c. phenolphthalein, 



plus 50 c.c. water ,, ,, 3-4c.c. ,, 



25 c.c. milk plus 1 c.c. phenolphthalein, 



plus 100 c.c. water , ... ,, ,, 3-35 c.c. ,, 



25 c.c. milk plus 1 c.c. phenolphthalein, 



plus 100 c.c. water at70°C, ,, 3*8 c.c. 



It has been invariably found that heating the milk increased 

 the amount of alkali to be added, and that dilution diminished 

 the amount up to a certain figure, and then further dilution pro- 

 duced only a slight effect.* It is customary to designate the 

 number of cubic centimetres of decinormal soda used to neutralise 

 100 c.c. milk as so many degrees of acidity. The figures obtained 

 for 25 c.c. milk have been multiplied by 4 to obtain this figure. 



Upon determining the degree of acidity of milk within one 

 minute after its removal from the mammary gland of the cow, it 

 has been found to vary from 12° to 19° acidity in 14 cows. The 

 figure for the mixed milk of the 14 cows at the end of milking 



*Compare Sbldner, Landw. Vers. -Stat., Bd. 35, S.354, 1888; and Siegfeld, 

 Hildesheim. Molkereiztg., 1900. 



