MILK TESTS 453 



Each notch that the larger weight is reversed has a value of 1 per 

 cent (reading on the upper scale), and each notch that the smaller 

 weight is reversed has a value of .1 per cent. If, for example, after 

 heating, the scales just balance when the larger weight rests on 15 

 (upper scale) and the smaller weight rests on .2, it would mean that the 

 sample contained 15.2 per cent moisture. 



Test for salt in butter (Ross) . 



Weigh out accurately, from a well-mixed sample, 10 grams of butter. 

 Add to the 10 grams of butter 100 cc. of hot water, and thoroughly mix 

 the butter with the water. Then cool to harden the fat, and pour off into 

 a clean dish the 100 cc. of water. Repeat this operation until 300 cc. 

 of water has been used. Thoroughly mix the 300 cc. of water, and meas- 

 ure out 17.5 cc. into a glass beaker or white cup, and add five or six 

 drops of potassium chromate. This will turn the solution a lemon- 

 yellow color. Run in from a burette an normal solution of silver 



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nitrate. Thoroughly mix the solution as the silver nitrate is added. 

 When the solution turns to an orange-yellow color, enough silver ni- 

 trate has been added to neutralize all of the salt. The number of cc. 

 of silver nitrate solution added equals the per cent of salt in the butter. 

 For example, if it requires 2 cc. of silver nitrate, there is 2 per cent 

 of salt in the butter. If more or less than 10 grams of butter are 

 used and more or less than 17.5 cc. of the solution are used for the 

 test, the burette will not give readings directly in terms of per cent. 

 Care should be taken not to run in too much silver nitrate. If too 

 much silver nitrate is used, the color will be a dull brick-red, and incor- 

 rect results will be obtained. An normal solution of silver nitrate, 



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which is accurate enough for the purpose, may be made by dissolv- 

 ing 17.5 grams of silver nitrate in 200 cc. of water and then making 

 the solution to 1000 cc. or 1 liter. 



Test for salt in cJieese (Ross). 



Burn to a gray ash in a porcelain dish 5 grams of the cheese. 

 Care should be taken to keep the contents in the center of the dish. 

 If this is done, it will make it easier to reduce the cheese to an ash. 



