ANALYSIS OF BUTTEE-FAT. 49 



Through the labours of Mr. J. A. Wanklyn, as is well 

 known, the analysis of milk, as regards the detection of 

 added water, has been placed on a sound basis, inasmuch 

 as he pointed out that the percentage of " solids not fat " 

 was nearly constant. No milk, yielded by an undoubtedly 

 healthy cow, has ever been found to yield less than 9'0 per 

 cent, of " solids not fat," although samples contaioing as 

 much as 11 -3 per cent, are to be met with. A milk con- 

 taining less than 9 per cent, may safely be declared to be 

 adulterated with water, j 



Similarly we are now in a position to say, with even a 

 greater degree of probability, that no sample of butter-fat 

 can be declared to be pure and genuine, unless the per- 

 centage of insoluble fatty acids be lower than 88'5 per cent. 

 But just as from 20 to 25 per cent, of water may be 

 added to milk of the very best quality, in order to depress 

 it to the lowest level, namely 9 per cent, of solids not 

 fat, so about 15 per cent, of foreign animal fat may be 

 added to a butter rich in soluble acids, the product being 

 equal to the lowest quality butter. In aU similar cases, the 

 dealer gets the benefit of the doubt, but there is a certain 

 limit which he cannot overstep with impunity. 



A judicious addition of any soluble substance, such as cane 

 or milk sugar to diluted milk, raises the percentage of the 

 " solids not fat " to their proper level, and adulteration would 

 in such cases be entirely overlooked, or could only be detected 

 by a careful analysis of the dissolved constituents. In the 

 case of butter, however, it is not possible to evade analysis 

 in a corresponding manner ; it might approximately be done 

 by the addition of a tri-glyceride of a soluble acid, but such 

 glycerides are only to be obtained from butter, or syntheti- 

 cally. But even then, as wiU appear from some observations 

 on the chemical constitution of butter-fat, it would not be 

 difficult to extract such added glyceride from the butter. 



s 



