228 THE ANALYSIS OF SOLID MILK PRODUCTS. 



degrees of acidity and aldehyde figure are obtained, and the 

 latter multiplied by 0-185 will give soluble protein. 



The colour of the solution should be noted. 



Acidity and Aldehyde Figure are estimated as for milk powders 

 (p. 219), and the protein is deduced by multiplying the latter 

 figure by 0-185. 



Phosphates and Glycerophosphates. Five grammes are trans- 

 ferred to a stoppered cylinder containing about 40 c.c. of warm 

 distilled water, and alkali is added little by little to dissolve 

 the casein till a distinct colour is shown to phenol-phthalein, 

 shaking well till dissolved completely, the solution cooled to 

 15 C., and made up to exactly 99 c.c. Four c.c. of Wiley solution 

 are added, and the whole shaken with much vigour till the pre- 

 cipitate is in a fine state of division, and filtered. 



To 20 c.c., 20 c.c. of molybdate solution (p. 289) is added, 

 and the mixture stood cold for three hours. After filtering into 

 a Gooch crucible, and washing by decantation four times with 

 2 per cent, nitric acid, and then six times with 10 c.c. of 1 per cent, 

 potassium nitrate, the seventh washing is tested, and it must 



not require more than 2 drops NaOH to give a pink colour 



to phenol-phthalein ; if still above this limit of acidity the washing 

 is continued till it is attained. The contents of the Gooch 

 crucible are washed back into the precipitating vessel, using about 

 50 c.c. of water, raised to the boil, 1 c.c. of 0-5 per cent, phenol- 

 phthalein solution added, and titrated hot to a faint pink with 



caustic soda. 



c.c. Y^T required X 0-0313 = P 2 5 as phosphates. 



To another 20 c.c. in a porcelain or silica basin lime (free 

 from phosphates) is added until pink, it is evaporated to dryness, 

 and ignited cautiously ; the ash is dissolved in strong nitric 

 acid and again evaporated, and dissolved in dilute nitric acid 

 with the addition of about 50 c.c. of water and 50 c.c. of molyb- 

 date solution, raised to 40, it is allowed to stand for fifteen 

 minutes, and filtered on a Gooch crucible, washing as before, 



N 

 but titrating with caustic soda, then 



c.c. N required X 0-95 = Na 2 G"lP0 4 . 



If the ash of 1 gramme is dissolved in strong nitric acid, 

 and treated exactly as above, the difference between the 

 titration of this molybdate precipitate and that obtained 

 above expressed as c.c. N X 0-313 will give the P 2 6 as organic 



