SOME PHYSICO-CHEMICAL MEASUREMENTS ON MILK. 



185 



7-0 



6-8 



^ 



6-7 

 10 125 150 175 2-0 



10% Fig. 1.— Concentration of Milk (Fresh Milk.) 100% 



Indicator Method. 

 Having found from E.M.F. measurements between what 

 values the H ion in the milk varies, it was decided to use 

 1 per cent, solution of methyl red and rosolic acid in alcohol 

 as indicators, to determine from colour changes the H ion 

 concentration. These two indicators have been found 

 satisfactory. 



It was soon found to be impossible to observe the change 

 of colour which takes place on adding a few drops of indi- 

 cator to milk owing to its opacity. It has however been 

 found practicable to add a few drops of milk to a small 

 quantity of indicator in water, and compare the colour 



