1 8 MILK AND DAIRY PRODUCTS PART 



kg. of milk a sample of half a litre would be taken, and from 

 one containing 30 kg., 300 c.c., and so on. These different 

 samples would then be thoroughly mixed in some convenient 

 vessel, and from this the main sample would be drawn. It is 

 more satisfactory, of course, to empty the contents of the various 

 cans or churns into a suitable vessel, and then, after a thorough 

 stirring, to take out the sample which is to be tested. 



Often enough it happens that the milk from which a sample 

 is to be drawn is allowed to stand so long that a thick layer of 

 cream, which does not easily mix again with the rest of the 

 milk, forms on the surface. In such a case it is only necessary 

 to warm the milk to about 40 C. by placing the vessel in which 

 it is contained into hot water, for afterwards it is easy to effect 

 a thorough mixing. 



When taking samples of milk from individual cows during 

 test milkings, a course which must be adopted if the milk pro- 

 duction of each animal is to be ascertained, then it is best to 

 use an apparatus similar to the one described below. 



The milk from each cow is weighed in the cylindrical vessel, 

 either on a weighing machine similar to the one shown in Fig. 5a 

 or on a spring balance, and then the glass tube shown on the 

 right of the figure is sunk to the bottom of the vessel. The 

 upper end of the glass tube is then closed with the finger so 

 that the milk cannot flow out, and the sample is in this way 

 transferred to one of the numbered bottles, one of which is sup- 

 plied for each cow. Similarly, at the other times of the day 

 when the cows are milked, a sample is taken, and the two or 

 three individual samples make a collective sample for the day's 

 milk. 



If the sample of milk is to be tested at once on the spot, no 

 special precautions are needed to preserve it ; but if, on the 

 other hand, one or more samples have to be forwarded to a 

 laboratory, this should be done in well-corked bottles, which 

 must be clean and dry before the milk is put into them. If 

 only the percentage of fat in the milk is to be determined, then 

 100 c.c. will suffice ; but if a fuller investigation is to be made, 

 then a larger quantity, say 500 c.c., should be taken. In 

 no circumstances, though, should the sample bottles be quite 

 full, for, if so, it would hardly be possible to get the cream, 

 which had separated out, back again into its normal state in 



