No. 6. DEPARTMENT OF AGRICULTURE. 645 



of fat. Matbiiies Avbic-h carry an even number of bottles are to be 

 preferred. The best form of machine for use in factories is a steam 

 turbine machine. Thej have the advantage of maiotaining an even 

 speed, they keep the bottles hot and supply distilled water for filling. 

 (5.) Commercial Sulphuric Acid (Oil of Vitriol). — This should have 

 a specific gravity of 1.S2 to l.So. If the acid is much stronger, the 

 fat will be dark in color and its amount hard to read. If the acid 

 is weaker than 1.82, there is liability of some casein remaining un- 

 dissolved and this will mingle with the fat and make the test un- 

 i^atisfactory. If the acid is too strong, good results may be secured 

 by using less. It is best to purchase acid at 1.82 or a trifle above 

 and not attempt to dilute the strong acid. Dairy-supply houses 

 should keep acids of the right strength made up in carboys for the 

 trade. The acid should be kept in tightly stoppered bottles, because, 

 if exposed to air, it rapidly absorbs moisture and becomes too weak. 

 The stopper should be of either glass or rubber and, in no case 

 should a common cork be used, since it would be quickly destroyed 

 by the acid. Sulphuric acid is extremely corrosive and is danger- 

 ous to handle except with care. It quickly ruins clothing or leather 

 on which it falls and seriously burns the skin if left in contact with 

 the acid for a few minutes. If sulphuric acid gets upon the skin 

 anywhere, it should be immediately and thoroughly washed with 

 abundance of water. Too great care can not be exercised in handling 

 this acid. 



80. How to Sample Milk for Testing. 



(1.) Conditions Making Sampling Difficult. — Milk that has soured 

 and thickened or in which cream has risen and dried, so as to 

 form a clot or skin, is difficult to sample properly and will gen- 

 erally be found to give low results. The same is true of milk in 

 which the fat has been partially churned and formed into little butter 

 granules that rise quickly to the surface. Such churning is liable 

 to occur in milk that is transported long distances in vessels that 

 are not full. However, these difficulties are seldom met in milk 

 that has received careful attention in its preliminary handling. 



(2.) How to Take a Sample of Milk for Testing. — The sample to 

 be tested is thoroughly mixed by pouring the milk from one vessel 

 to another two or more times, thus making every part of the milk 

 contain the same amount of fat. If the pipette is Bot dry, when 

 used, it should be filled with the milk to be tested and then thrown 

 away before taking the sample for testing. The measuring pipette 

 (see Fig. 9), is at once filled with milk after the mixing by sucking 

 up the milk into it, until it reaches above the mark on the stem 

 of the pipette. Then the forefinger, which must be dry, is quickly 



