CHAPTER II 

 THE ANALYSIS OF MILK 



Preparation of the Sample. A milk sample con- 

 veniently consists of a five-ounce bottle filled nearly 

 full ; if the sample is to be representative of a bulk, 

 the milk (whether in a churn, pail, can, or jug) 

 should invariably be well stirred before the sample is 

 taken in order to distribute the cream which always 

 tends to rise to the surface. Samples taken in a dairy 

 or other place for testing on the premises may, how- 

 ever, be taken in cans, and if the sample is one 

 frequently taken from the same source a distinguishing 

 mark may be stamped on the can. 



On receipt of the sample in the laboratory it should 

 invariably be stirred before any portion is withdrawn 

 for analysis ; violent shaking is to be deprecated, as 

 not only is there a tendency to churn the fat but air 

 bubbles, which do not separate immediately, are in- 

 cluded, and prevent accurate measurements, especially 

 of specific gravity. In cold weather samples are often 

 frothy, and while they remain cold the air bubbles 

 separate very slowly. Freshly drawn milk is also 

 frothy, and the fat being in the liquid condition has a 

 lower specific gravity than it has after solidification. 

 If the sample is turning sour there is often difficulty in 

 uniformly distributing the cream, and violent shaking 

 may have to be resorted to ; if any of the fat is churned 

 or becomes churned in this operation, the lumps of 

 churned fat should be removed, dried, and the fat 

 extracted with ether and weighed ; the total weight of 

 milk is ascertained, and the percentage of churned fat 

 calculated. The remainder of the sample is analysed 

 separately. 



Milk which is sour and curdled is mixed by turning 



