Dairying 



379 



the fat. An acid that has over 1.83 specific gravity has a 

 tendency to char the fat and should not be used. The acid 

 must be kept in glass 

 bottles that are fitted 

 with glass stoppers. 



In making a test, 

 these directions should 



FIG. 155. A dipper made entirely of glass and 

 holding 17.5 cubic centimeters for measuring 

 the acid. 



be followed: Mix 



thoroughly the sample 



to be tested, place the pipette in the milk, and suck milk into 



the tube until it is above the level of the etched line on the 

 neck. Place the forefinger over the end of the 

 pipette and the milk will remain in the tube. Re- 

 move the pressure of the finger slightly and allow 

 the milk to run out of the end of the pipette until 

 it is on a level with the etched line, thus leaving 

 17.6 c.c. of milk in the pipette. Place the end of 

 the pipette in the neck of the test bottle and allow 

 the milk to flow into the bottle. Fig. 159 shows 

 the correct way to hold the bottle and the pipette. 

 If they are both held in a vertical 

 position the milk is almost sure to 

 spill (Fig. 160). Next, fill the acid 

 measure with acid (17.5 c.c.) and 

 pour it into the test bottle. Slant 

 the bottle as before. If the acid has 

 been poured into the milk carefully, 

 the two liquids will be in two layers 

 in the bottle. Mix the acid and 

 uring the milk by gently rotating the bottle. 



Continue this rotating until all pieces FIG. 157. Acom- 



of curd that form in the mixture are dissolved. bin <r d bottle and 



. acid measure. 



Allow the mixture to stand a few minutes, then 



rotate the bottle again for a short time. Place the bottles in 



the tester in an upright position. The tester should be full of 



FIG. 156. 

 Burette 

 for meas- 



