A DAIRY LABORATORY GUIDE 59 



tion of potassium chromate (K2Cr O4). This 

 indicator added to sodium chloride solution 

 produces a lemon yellow color. When enough 

 silver nitrate has been added to just neutral- 

 ize all of the sodium chloride the solution 

 turns a light brown color. No more silver 

 nitrate should be added when a permanent 

 light brown color is obtained. 



The chemical reaction which takes place is as 

 follows : 



Nacl+Ag No3=Na Nos+Agcl 



One cc. of n/io silver nitrate solution will neu- 

 tralize .00585 grams of sodium chloride. Since 

 the butter is in solid form, it is necessary to 

 dissolve the sodium chloride and this is done 

 by washing the butter in a definite amount 

 of warm water, and titrating the water. 



Suppose 10 grams of butter are washed in 200 

 cc. of warm water and it takes 6 cc. of silver 

 nitrate solution to neutralize the salt in 50 cc. 

 of the wash water. It would then require 24 

 cc. of silver nitrate solution to neutralize the 

 salt in 200 cc. of wash water. Since i cc. of 

 silver nitrate will neutralize .00585 grams of 

 salt (sodium chloride) 24 cc. will neutralize 

 .1404 grams of salt (24x.oo585=.i404). 



This salt was obtained from 10 grams of butter 

 so .1404 grams of salt divided by 10 grams of 

 butter, and the quotient multiplied by 100 

 will give 1.404 the per cent of salt in the but- 

 ter. 



