124 



ANALYSIS OF MILK. 



Ttis experiment siio-ws that a portion of tte proteins is removed 

 ■with, the fat, and corroborates the author's conclusion that -when 

 the portion run through in the first fifteen minutes is taken, 

 there is only a slight loss of solids not fat. 



The author has found that if the specific gravity of the filtered 

 milk less 1 be divided by 0"004, and the difference between the 

 specific gravities of the milk before and after filtration be divided 

 by O'OOOS, the figures so obtained very fairly represent the solids 

 not fat and fat respectively. The folio-wing figures (Table XI.) 

 will show the agreement that may be expected : — 



TABLE XI. — Estimation op Milk Solids by Densimeteic 



Method. 



Great accuracy cannot be expected from this method, but it 

 has the advantage of not requiring chemical apparatus. Deter- 

 minations can be made with a small delicate lactometer, and an 

 idea of the quality of a milk obtained in a short time. 



The Estimation of Proteins. — Proteins may be either estimated 

 collectively as total proteins, or separate determinations of casein 

 and albumin can be performed. 



Total Proteins from Total Nitrogen. — The determina- 

 tion of total proteins is generally performed either by making 

 an estimation of total nitrogen in milk, and multiplying this 



by 6-38 (= T^, as both casein and albumin contain this amount 



of nitrogen), or by precipitating the proteins as copper salts by 

 Ritthausen's method. 



Kjeldahl's Method. — To determine total nitrogen the method 

 of Kjeldahl is the most convenient. Five grammes of milk are 

 weighed into a round bottomed hard glass flask of about 150 c.c. 

 capacity and 20 c.c. of pure sulphuric acid added. This is 

 placed over a small flame and heated till it is thoroughly 

 charred, the water being evaporated during this heating ; the 

 flame is now removed, and about 10 grammes of potassium 



