METHODS OF TESTING THE ACIDITY OF MILK 143 



terial is taken for the test. In making the test, the solu- 

 tion is poured from a 100 cc. graduated cylinder. 



In preparing the alkali solution, 5 tablets are put 

 into the 100 cc. cylinder which is then filled to the 97 

 cc. mark with clean, soft water, preferably distilled. 

 The cylinder is then tightly stoppered and laid on its 



side until the tablets dis- 

 solve, which requires seve- 

 ral hours. The cylinder 

 must be kept tightly stop- 

 pered so that none of the 

 solution can be lost while 

 the tablets are dissolving. 

 A slight flocculent residue, 

 consisting of some inert 

 matter used in making the 

 tablets, will not dissolve. The solution should always 

 be shaken well before using. When not in use, it 

 should be kept tightly stoppered. Solutions that have 

 been prepared longer than a week may change in 

 strength and it is better to prepare fresh solutions 

 than to use old ones. The solid tablets do not change 

 if kept dry. 



FIG. 380 FARRINGTON'S 



ALKALINE-TABLET TEST 



FOR ACIDITY 



Spillmaris Modification of Farrington's Test 



The apparatus consists of an ordinary teacup, a reg- 

 ular 17.6 cc. pipette, a quart Mason fruit- jar, and 

 "Spillman's .acid-test cylinder" (Fig. 38!)). The alkali 

 solution is prepared by dissolving alkaline tablets in 

 water at the rate of 5 tablets for one cylinder of water 

 filled to the mark 8, the solution being made and kept 



