162 Canadian Record of Science. 



in two ways : by the addition of water and by the abstrac- 

 tion of cream. 



The detection of adulteration depends upon our ability 

 to determine whether cream has been abstracted or water 

 added. Pure milk contains 87 per cent, water, and unless 

 the added water introduces some impurity which we can 

 detect by anatysis, there is no way of distinguishing it 

 qualitatively from that of the natural milk. Certain tests 

 have been proposed for this purpose. Thus it has been 

 suggested that added water may be detected by the nitrates 

 it contains, but our public supplies from the great lakes 

 and river are practically free from nitrates. The presence 

 of sulphates has also been regarded as proving the addition 

 of water, the old analysis of milk ash showing either 

 the merest traces of sulphates or none at all. But the 

 recent analyses of Schrodt and Hansen, already quoted, 

 demonstrate that milk ash contains nearly ± per cent, of 

 its weight of sulphuric acid as sulphates, so that in nearly 

 every case we are obliged to form an estimate of the purity 

 of the milk by determining the amount of solids and fat it 

 contains, and comparing our results with the composition 

 of genuine milk. 



The methods used for milk analysis have had much 

 attention bestowed upon them. We owe a deep debt of 

 gratitude to Mr. Wanklyn for shewing us how a milk 

 analysis can be simply and accurately effected. His book 

 was published in 1873, and his method was to dry the milk 

 on a water bath in a little flat-bottomed platinum dish and 

 weigh the residue, and to extract the fat from such a 

 residue with ether, evaporate the ether and weigh the 

 residual fat. In this way he obtained the total solids and 

 the fat. By subtracting the fat from the total solids he 

 obtained the solids not fat, and he was the first to show the 

 great value of this determination. He pointed out that of 

 all the constituents of the milk, the fat was the only one 

 which varied very much in quantity, the percentage of the 

 other solids only differing within comparative^ narrow 

 limits in genuine milk, whether rich or poor. 



Wanklyn maintained that the solids not fat in genuine 



