METHODS OF TESTING MILK FOR SALT I2/ 



paper. This means that the chloride has all become 

 precipitated or changed to solid silver chloride, and 

 that silver chromate is formed and remains in the mix- 

 ture. When this point is reached, add no more silver 

 solution. Examine the burette and read the number 

 of cubic centimeters of silver nitrate solution that has 

 been used. Suppose we findv we have used 20 cc. ; 

 this means that the 10 cc. solution tested contains 0.20 

 gram of salt, since i cc. of silver solution precipitates 

 the chlorine in o.oi gram of salt. This is equal to 

 about 2 per cent, of salt in the solution. 



Several applications have been made for the deter- 

 mination of salt in butter, the difference in methods 

 being the preparation of sample, strength of silver 

 solution and amount of material taken for testing. 

 At one time silver nitrate tablets were on the market. 



It will probably be found best to purchase the silver 

 nitrate solution from some reliable chemical-supply 

 house. When, however, the solution is made at home 

 from silver nitrate crystals purchased at .a .drug-store, 

 only the pure compound should be used. In dissolv- 

 ing silver nitrate in water, it is best to use distilled 

 water or rain-water. Water which produces any 

 marked turbidity when treated with a few drops of 

 silver nitrate solution should not be used in preparing 

 silver nitrate solutions. 



\yPERKINS TEST FOR SALT IN BUTTER 



This was devised at the Ohio experiment station 

 and can be carried out more quickly than other 

 methods. 



The solutions used are: (i) A solution of silver 



