TESTING ACIDITY OF MILK AND MILK PRODUCTS 97 



and 17.6 cc. is then measnred into a clean porcelain 

 cup with a pipette. The pipette is rinsed by filling with 

 water, which is added to the sample in the cup. The 

 tablet solution prepared in the manner described is 

 poured slowly into the cup in small portions at a time, 

 and the mixture is agitated by rotating the cup after 

 each addition of alkali. When the pink color does not 

 disappear readily on agitating (p. 94), the number of 

 cubic centimeters of alkali used is read from the grad- 

 uated cylinder. Each cubic centimeter of alkaline-tab- 

 let solution used equals .01 per cent, of lactic acid in 

 the sample tested. For example, the use of 25 cc. of 

 alkali solution equals .25 per cent, of acid; 40 cc. 

 equals .40 per cent., etc. 



SPILLMAN'S MODIFICATION OF 

 ALKALINE-TABLET TEST 



The apparatus consists of an ordi- 

 nary teacup, a regular 17.6 cc. pipette, 

 a quart IMason fruit-jar, and "Spill- 

 man's acid-test cylinder" (Fig. 39). 

 The alkali solution is prepared by dis- 

 solving alkaline tablets in water at 

 the rate of 5 tablets for one cylinder 

 of water filled to the mark 8, the so- 

 lution being made and kept in the 

 fruit- jar. Observe the precautions 

 given above in using tablet solutions. 

 In making the test, put 17.6 cc. of 

 the material to be tested in a teacup, 

 pour into the cup the alkali solution in the manner de- 

 scribed above, until the pink color remains. Then 



•fc- 



FIG. 39 



spillman's acid- 

 test CYLINDER 



