MILK RECORDS S/ 



specific gravity of about 1.82, is used in making the 

 test. It should be used at a temperature ranging 

 from 50 to 70 F. and always kept in a tightly stop- 

 pered bottle. Care must be taken in mixing the acid 

 with the milk ; 17.5 c. c. are measured into the acid 

 graduate and slowly turned into the test tube in 

 such a way that it runs down on the inside of the 

 bottle rather than directly into the milk, to prevent 

 burning the milk solids. A complete mixture is 

 effected by holding the bottle by the neck and giv- 

 ing it a gentle rotary motion. The action of the 

 acid causes a rapid increase in temperature, at the 

 same time dissolving all the non-fatty solids of the 

 milk and making possible a rapid and complete sepa- 

 ration of the fats. 



The test bottles and contents are now placed in the 

 centrifugal machine and whirled at the required 

 speed, which varies with the size of the machine. 

 The bottles assume a horizontal position, and as the 

 fats are the lighter part of the milk they rise to the 

 surface. With the hand machine full speed should 

 be maintained for five or six minutes for the first 

 whirling, after which enough hot water should be 

 added to the contents of the bottles to float the fat 

 within the limits of the graduated scale on the neck 

 of the test bottle. The bottles are whirled again for 

 two or three minutes at full speed, after which they 

 should be placed in hot water (temperature 125 to 

 140 F.) to keep the fat in a clear liquid state for 

 reading. If when managed in this way clots of curd 

 or other matter are mingled with the fat, making the 

 reading uncertain, the difficulty can usually be 



