THE FAT. 



25 



order to facilitate the solution of tlie fat, the milk residue 

 may be first moistened with alcohol, which will tend to dis- 

 integrate it, and favor the action of the ether upon it. 



With regard to the quality of the ether employed, it 

 should be tolerably dry ; but it may be methylated ether. 

 Of course it should leave no appreciable residue when 50 c. 

 c. of it are evaporated and dried in the water-bath. The 

 cost of such ether is about 16s. per gallon, and the cost of 

 the ether consumed in each determination of fat is not more 

 than twopence. I would, however, give the advice to be 

 liberal with the ether ; for it is false economy to ruin the 

 determination for the sake of saving ether. 



As will be apparent on trying practically to make these 

 determinations of fat, the yield from 5 c. c. of milk is rather 

 inconveniently small. I prefer to take 10 c. c. of milk, and 

 to evaporate down in a larger platinum dish. A dish capable 

 of holding 40 c. c., which costs about 80s., will answer very 

 well. A small platinum spatula may be inserted into the 

 milk, and used to stir it up occasionally during the evapo- 

 ration. In this instance, it is unnecessary to push the drying 

 of the milk-solids to completeness, and an hour's evapora- 

 tion in the water-bath is amply sufficient for the purpose. 

 Just at last, the milk residue should be moistened with 

 alcohol to soften it. The mode of dissolving out the fat with 

 ether, and the passing of the ethereal solution through the 

 filter, and the subsequent treatment of the residual rim of 

 fat in the filter paper, has been already explained. 



The ethereal solution of fat having been obtained (and, by 

 the way, it ought never to be less than 50 c. c.), the next 

 point to be attended to is the evaporation of the ether, and 

 the getting of the residue of fat. 



In laboratories where there is a platinum dish capable of 

 holding 100 c. c., such as is used in taking water residues, 



