128 MODERN METHODS OF TESTING MILK 



nitrate containing 29.06 grams per liter; (2) commer- 

 cial acetone (or equal parts of denatured alcohol and 

 ordinary ether) ; (3) saturated water solution of potas- 

 sium chromate. The apparatus required is a 50 cc. 

 burette, accurately graduated to o.i cc., together with 

 a white cup or beaker. 



The operation of the test is performed as follows: 

 Weigh in a cup or beaker 5 or 10 grams of butter from 

 a sample prepared as previously directed (p. 101). 

 Warm gently until just melted and then add 20 or 

 30 cc. of commercial acetone (obtainable at any good 

 drug-store) or, if acetone is not easily obtainable, use 

 the mixture of denatured alcohol and ether; add about 

 i cc. of the chromate solution, and then run in slowly 

 from the burette the solution of silver nitrate, vigor- 

 ously stirring or shaking the mixture. Continue to 

 add the silver solution until the brick-red color remains 

 permanent for a minute or more after thorough agita- 

 tion. Each cubic centimeter of silver nitrate solution 

 used represents o.i per cent, of salt in the butter when 

 a lo-gram sample of butter is taken, and 0.2 per cent, 

 with a 5-gram sample. For example, if 25 cc. are 

 used, the result would be 2.5 per cent, of salt in the 

 butter when a lo-gram sample is taken. 



This test can be applied in connection with the de- 

 termination of water by most methods. Thus, the 

 dried residue obtained with the Cornell, Wisconsin, 

 Ames, Patrick and similar methods can be used for 

 salt determination by adding a small amount of water 

 and carrying out the operation described in the pre- 

 ceding paragraph. 



