86 THE BUSINESS OF DAIRYING 



the test and how it is operated. The outfit consists 

 of a pipette for measuring the milk sample, an acid 

 measure, test bottles graduated to lo per cent., and 

 a centrifugal machine for whirling the bottles and 

 contents at high speed. Small machines are easily 

 operated by hand, while large ones require power. 



The important thing at the outset is to secure a 

 fair sample of the milk to be tested. This is accom- 

 plished by thoroughly mixing the milk by repeatedly 

 pouring it from one vessel to another. It is then in 

 condition to sample. The sampling may be done by 

 using a small dipper. Owing to variations in the 

 composition of the milk from day to day and in the 

 morning's and evening's milk of the same day, it is 

 necessary to collect several samples if accurate re- 

 sults are to be secured. These may be brought to- 

 gether for two or three days and made into a com- 

 posite sample before the test is made. A few drops 

 of formalin or a little potassium bichromate may be 

 used to keep the sample sweet. The composite 

 sample thus obtained should be thoroughly mixed. 

 The pipette is then drawn nearly full of milk by 

 placing the mouth at the end ; the forefinger is then 

 quickly placed over the top end of the pipette as it 

 is removed from the mouth ; the pipette is held on a 

 level with the eye, while the milk is allowed to run 

 out slowly until its surface is even with the 17.6 

 mark. The pipette is then inserted far enough into 

 the test tube to allow the milk to run in without 

 spilling. After the pipette has drained, the last drop 

 is blown from it and the sample is ready for the acid. 



The ordinary commercial sulphuric acid, having a 



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