68 SCIENCE AND PRACTICE OF DAIRYING. 



above-mentioned constituents, i.e. the percentage of "solids not 

 fat " (r), and lastly the specific gravity of the total solids (m). 



When it is desired to make an analysis of milk, it is of the 

 greatest importance to obtain a true average sample, this being 

 effected by thoroughly mixing the milk before taking the sample. 

 In this connection, it must not be forgotten how quickly milk 

 changes, owing to the tendency the fatty globules have to rise to the 

 surface. Thorough mixing of the milk, therefore, before taking the 

 sample, must never be neglected. When necessary, the milk should 

 be warmed to 40 C. before sampling. 



Especial care should be taken in the determination of the specific 

 gravity (s), and to do so, if possible, up to the ten-thousandth 

 figure. For this purpose a glass hydrometer, of the Soxhlet pattern, 

 should be used, in which the divisions indicating thousandths should 

 occupy 7 '5 mms. The temperature of the milk should also be 

 observed, and the results should be corrected, by means of correc- 

 tion tables, to the temperature of 15 C. if the specific gravity has 

 not been taken at that temperature. Special attention ought to 

 be paid to the fact, that freshly-drawn milk yields figures from J 

 to TTr Vffth less than the figures yielded by the same milk, even 

 after the lapse of so short a period as three hours. On this account 

 one can only accept the specific gravity of milk as final when the 

 milk has stood for three hours from the time it was milked. The 

 fat (/) is determined, either by gravimetric methods or by Soxhlet's 

 areometric method, or with the lactocrit. If (s) and (/) have been 

 obtained, the total solids (t) may be calculated by means of formula 

 (3) given in 11. 



f 



If, from the value found for (t), the value for (/) be deducted, 

 the value (r) (viz. the "solids not fat") is obtained: 



From formula (7), given in 11, the value of (m) (viz. the specific 

 gravity of the total solids) can be calculated: 



This value (m) is altered by creaming the milk, but not by water- 

 ing it. The knowledge of the five values, (/), (t), (s), (r), (m), is 



