58 MILK- ANALYSIS. 



lot. This is, perhaps, best done by taking two specimens, 

 one from the edge of the butter, and another from the centre. 

 About one gramme of but ter is enough for the estimation of 

 water. This is to be weighed into one of the little platinum 

 dishes, and dried in the bath as if it were a milk-residue. 

 After three hours' drying it should be weighed, and returned 

 to the bath, and weighed at intervals of an hour till constant. 

 The drying up of butter is tedious, like the drying up of 

 cream. Having dried it up, the residue is to be dissolved in 

 dry ether, filtered, and the ethereal solution evaporated to 

 dryness, and the residue dried in the water-bath. This 

 second drying is a very easy one. 



The mineral matter is estimated by burning off the fat and 

 weighing the residue. 



The " organic matter not fat " may be estimated by differ- 

 ence. It may also be estimated directly. For this purpose 

 several grammes of butter are weighed out, and dried for a 

 short time in a platinum dish in the water-bath, and then 

 subjected to the action of dry ether, which will dissolve out 

 the fat and leave the rest. The ethereal solution is to be 

 decanted off, and the residue dried up in the water-bath, 

 weighed, and ignited, and again weighed. The difference 

 between the two weights is the weight of the organic matter 

 not fat. 



With regard to the question of admixture of foreign fats 

 with milk-fat, we are unable, in the present condition of our 

 knowledge, to deal with that part of the problem. 



As has been said, milk-fat is a mixture of the ethers of 

 glycerine, which constitute the common fats. It contains, it 

 is true, a trace of butyrine, in addition to the commoner 

 glycerides ; and it is possible that, by an extraction of the 

 butyric acid, we might arrive at data of some value in 

 forming a judgment of the quality of the fat. But investi- 

 gation is required before that could be depended upon ; and 



