CHAPTEE IV. 



THE FAT. 



THE fat in milk is estimated by dissolving it in ether (which 

 dissolves it, but does not dissolve any other constituent of 

 milk), and evaporating the ethereal solution to dryness, and 

 weighing the dried residue. It is not practicable to apply 

 the ether directly to the milk itself, but the ether must be 

 applied to the dry milk-solids. 



The residue obtained, as described in last chapter, by 

 evaporating, and drying up 5 c. c. of milk, may be taken for 

 the determination of the fat. 



This residue, as will be understood, is contained in a small 

 platinum dish. Ether is to be poured into the dish, and 

 heated to the boiling point, and poured out through a small 

 filter. This operation of boiling and pouring off the ethereal 

 solution must be repeated at least three times, and care is 

 required to let none of the fat make its escape over the 

 bottom of the dish. The filter should be large enough to 

 avoid the chance of spilling the ethereal solution as it is 

 being poured on to the filter. It is advisable to wash the 

 bottom of the little platinum dish with ether, in order to 

 avoid all chance of loss. Attention must also be paid to the 

 filter-paper after the ether has passed through it. Of course 

 it will require washing with ether ; and after the residual 

 ether has evaporated off, will be found with a little rim of fat 

 surmounting it. This is best dealt with by cutting it off, 

 and macerating it with a fresh portion of ether, which may 

 then be rapidly poured through a second small filter. In 



