342 



BUTTER. 



nut oil yields fine needle-sliaped crystals ; a mixture shows 

 the granular butter spores, with numerous Hue, almost feathery, 

 crystals generally attached to the butter granules. 



Five per cent, of coco-nut oil can be detected by this test. 



The Density of Butter Pat. 



Butter fat, on account of the presence of glycerides of low 

 molecular weight, has a greater density than the fats used for 

 its adulteration. As it is more convenient and exact to take 

 the density of a liquid than of a solid, the fat is almost invari- 

 ably melted and the density determined at a temperature above 

 its melting point. 



The methods of estimating the density have already been 

 discussed under the " specific gravity of milk " (p. 60), and 

 (except that for butter a temperature considerably higher than 

 that at which the density of milk is taken is employed) the 

 same methods are employed. 



Expansion. — Two questions arise : At what temperature 

 shall the density of butter be taken ? How shall the results be 

 expressed ? The experiments of Skalweit have indicated the 

 most favourable temperature. He took the densities of butter 

 and margarine at various temperatures from 35° C. to 100° C, 

 using Koch's incubator to keep a constant temperature. 



His figures are as follow : — 



Mode of Expressing Results. — These figures clearly show 

 that as the temperature rises the densities of butter and mar- 

 garine tend to approach one another ; the widest difference 

 occurs at 35° C. ; he, therefore, recommends that this temperature 

 be adopted as the temperature at which the densities of butter 

 should be determined. 



In England a large number of determinations have been made 

 by J. Bell, Allen, Muter, and others at a temperature of 100° F. 



