290 SALTrNO AND WORKING OF BUTTER 



To Make a Salt Test. — Either weigh out lo grams of butter, 

 or take the residue from the lo grams of l^utter used in the mois- 

 ture test; and rinse thoroughly into a suitable fiaslc, with a 250 

 CO. mark on it, using distilled water at a temperature of iio'^ 

 to 120° F. for the purpose, and making up to 250 c.c. with dis- 

 tilled water at the same temperature. Mix thoroughly to dis- 

 solve all the salt. 



25 c.c. of the salt solution are then transferred to a white 

 enamel cup, and to this are added 2 to 3 drops of indicator (a 

 10 per cent solution of potassium chromate) from a brown glass 

 dropping bottle. 



The silver nitrate solution is then added from a burette, and 

 mixed as it is added, until a permanent, light brick-red color 

 appears. 



Note the quantity of silver nitrate solution required to 

 make the test. If, for example, it requires 2.7 c.c. of silver 

 nitrate solution to make the test, this indicates that there is 

 2.7 per cent of salt in the butter; if it takes 3.8 c.c. of silver 

 nitrate solution, the per cent of salt in the butter is 3.8, etc. 



Note. — If the salt solution were made up to 100 c.c. instead 

 of 250 c.c, we could take 10 c.c. instead of 25 c.c. of this solution 

 to a test and read the per cent of salt direct, just as above. In 

 both cases we take a tenth of the solution or a tenth of the salt 

 in the lo-gram sample of butter. 



Another combination that will read the per cent of salt 

 directly : 



(i) A tenth normal (N/io) solution of silver nitrate, that is, 

 17 grams of silver nitrate in 1000 c.c. of the solution. (The 

 molecular weight of silver nitrate being 170, there are 170 grams 

 in 1000 c.c. of a normal solution, and a tenth of this in a tenth 

 normal solution.) 



(2) 10 grams of butter, the salt in it, being di.ssolved in 

 300 c.c. of water. 



(3) By means of a 17.6 c.c. pipette we take 17.5 c.c. of the 

 salt solution to a test. 



Each c.c. of silver nitrate solution required to make the test 

 indicates 1 per cent of salt in the butter. 



