CHAPTEE VI. 



MILK-StroAR. 



After the milk-solids have been deprived of fat by means 

 of ether, as explained in Chapter IV., they may be made to 

 yield up the milk-sugar, if they be treated with alcohol 

 and hot water. This has been explained in the preceding 

 chapter. 



It remains here to follow the weak alcoholic solution after 

 its passage through the filter on which the caseine had been 

 deposited. The solution is to be evaporated to dryness in the 

 water-bath, and the residue adherent to the vessel in which 

 the evaporation is performed, is to be weighed along with 

 its containing vessel. 



That having been done, it is ignited gently, and the residue 

 on ignition subtracted from the total weight before ignition. 

 The difference is the yield of milk-sugar. Multiply this by 

 10, and the number of grammes of milk-sugar yielded by 100 

 cubic centimetres of milk is found. With some chemists, a 

 titration of milk-sugar, by moans of copper solution, is in great 

 favor. For this purpose 50 or 60 c. c. of milk are gently 

 warmed and mixed with a little acetic acid in order to pre- 

 cipitate the caseine, which is separated by means of a filter. 

 The filtrate is used in the titration in the following manner: — 

 It is first diluted with nine times its volume of water, so that 

 one litre contains the milk-sugar of 100 c. c. of milk. A 

 measured quantity of standard copper-solution is then placed 

 in a white basin, and diluted with four times its volume of 

 water, and heated to boiling. Into it, whilst boiling, is 



