BUTTER 53 



for the volume of precipitated solids may be made by the 

 double-dilution method. The total reducing sugar is estimated 

 in one of the portions by one of the reducing methods, and if 

 the sum of it and the amount of cane-sugar obtained by in- 

 version is equal to that obtained by the direct reading of both 

 sugars before inversion, no invert-sugar is present. If the 

 amount of reducing sugar seems to be too great, the milk-sugar 

 must be re-determined as follows: 250 grams of the condensed 

 milk are dissolved in water, the solution boiled, cooled to 80, 

 a solution of about 4 grams of glacial phosphoric acid added, 

 the mixture kept at 80 for a few minutes, then cooled to room 

 temperature, made up to mark, shaken, and filtered. It may 

 be assumed that the volume of the precipitate is equal to that 

 obtained by mercuric iodid solution. Enough sodium hydroxid 

 is then added to not quite neutralize the free acid, and sufficient 

 water to make up for the volume of the solids precipitated by 

 the phosphoric acid. The mixture is then filtered and the fil- 

 trate is measured in portions of 100 c.c. into 200 c.c. flasks. A 

 solution containing 20 milligrams of potassium fluorid and half 

 a cake of compressed yeast is added to each flask, and the mix- 

 ture allowed to stand for 10 days at a temperature between 25 

 and 30. The invert-sugar and cane-sugar are fermented and re- 

 moved by the yeast in the presence of a fluorid, while milk-sugar 

 is unaffected. The flasks are filled to the mark and the milk- 

 sugar determined either by reducing or by the polariscope. 

 The amount of copper solution reduced by the lactose and invert- 

 sugar, less the equivalent of lactose remaining after fermenta- 

 tion, is due to invert-sugar. 



BUTTER 



Butter is a mixture of fat, water, and curd. The water con- 

 tains milk-sugar and the salts of the milk. Common salt is 

 usually present, being added after the churning. Artificial 

 coloring is frequently used. 



