4: ANALYSIS AND ADULTERATIONS OF BUTTER. 



alcohol, from which, it crystallises on cooling in shining 

 laminae, having a silky appearance when dry. It very 

 readily dissolves in ether. It has, like most other solid tri- 

 glycerides, three different melting points, 46 C., 61 '7, and 

 62-8 (Duffy). It solidifies at 45 -5 C. 



Palmitin occurs abundantly in many solid natural fats, 

 animal or vegetable, especially in palm oil, and in Chinese 

 tallow. The solid part of butter-fat appears for the most part, 

 if not entirely, to consist of tri-palmitin or a substitution 

 product, which yields palmitic acid and butyric acid on 

 decomposition. 



Palmitic acid, C 16 H 32 2 closely resembles in its physical 

 appearance the corresponding tri-glyceride. It is a white 

 solid, quite insoluble in water, than which it has a lower 

 specific gravity, is abundantly soluble in alcohol, especially 

 when hot, and in ether. It melts at 62 C. 100 parts of 

 palmitin yield 95*28 parts of palmitic acid. 



Stearin, C 57 H 110 6 or C 3 H 5 (C 18 H 35 2 ) 3 crystallises in 

 white, silky laminse and needles. It is nearly insoluble in 

 cold, but easily so in boiling alcohol. It dissolves freely in 

 boiling ether, but on cooling it separates, only 0'4 in 100 

 parts of the liquid remaining in solution. The solubility 

 in alcohol or ether is, however, much altered in the presence 

 of olein and other glycerides. 



It melts at 51-7, 6"4'2, and 69'7 in its three distinct 

 modifications, in which also it exhibits widely different 

 specific gravities, namely, 0'9867, T0101, and 1/0179 re- 

 spectively, at 15C. 



The presence of tri-stearin in butter-fat is doubtful. 

 Thus the substance, which Chevreul obtained from butter, 

 and which he regarded as stearin, had a far lower melting 

 point than pure stearin. We were not able to obtain any 

 magnesium salt, on fractional precipitation, which had the 

 composition of stearate of magnesia. 



