THE ANALYSIS OF MILK 



39 



of milk at least I c.c. of 0.5 per cent, phenolphthalein 



solution is added, and the milk 



neutralised with 

 ii 



(approximately) strontia solution ; to the faintly pink 

 liquid 2 c.c. or more of Schermg's 40 per cent, form- 

 aldehyde solution is added, and the titration continued 

 till the same degree of pink colour appears.. After 

 deducting the acidity of the formaldehyde solution, 

 the latter titration represents the aldehyde figure. The 

 aldehyde figure is obtained by multiplying the number 

 of c.c. used by the strength of the solution (see p. 95) 

 and by 1000, and dividing by the volume taken. Pro- 

 teins may be deduced from this figure by multiplying 

 by 0.170 ; this factor is only applicable f A 



to fresh cow's milk when determined by 

 strontia solution. 



Catalase. For the estimation, the 

 measuring cylinder is filled with water 

 through the opening rf, the cover of which 

 is then screwed down. The opening b 

 (for cleaning the tube) is closed with a 

 rubber cork, and the chamber A is 

 charged, through the opening c, with 15 

 c.c. of the milk and 5 c.c. of 1 per cent, 

 hydrogen peroxide solution (or 9 c.c. of 

 milk and 3 c.c. of hydrogen peroxide). 

 The tube is now held at / and d and 

 shaken with a pendulum motion, and 

 the cover to c rapidly screwed down. 

 The tube is then placed in water at 

 25 C. up to the level of c, shaken from 

 time to time, and the volume of the 

 liberated gas which rises into the measur- 

 ing chamber B read off after two hours. 



The Relation between Fat, Solids ,, 



i *f* ** z A J?IG.24. LiObecks 



not Fat, and Specific Gravity. As C ataiase Tube. 



the solids not fat of milk are heavier than 



water, and the fat is lighter, and as, moreover, the extent 



to which each of these is heavier or lighter respectively 



