EXPANSION OF FAT. 15 



The figures calculated are based on the assumption that the 

 expansion is regular between 15 and 100, and that the increase 

 of specific volume averages 0-000863 for each degree Centi- 

 grade ; on this assumption the specific volume of liquid fat 

 at 15 is higher, and the specific gravity is lower than that 

 of the solid. 



-I p* KO 



The specific gravity of liquid fat at ^-^o (calculated) is 0'922. 



It is interesting to note that the specific gravity of the liquid 

 fat obtained by the author (above) had a specific gravity of 

 0-922. The specific gravities of the liquid fats obtained by 

 Pizzi appear to have been taken at the temperature at which 

 the fat was separated, and on calculating to 15 have values from 

 0-921 to 0-925. 



On the whole the evidence available appears to show that the 

 specific gravity of solid fat is greater than that of liquid fat at 

 the same temperature. 



In connection with this, it may be mentioned that E. W. T. 

 Jones has shown that the specific gravity of other fats is greater 

 when partially solidified at 37-8 than when liquid at this tem- 

 perature. 



The index of refraction of the fat of milk averages 

 1-4566 at 35, and the limits observed have been 1-4550 

 to 1-4586. 



Stohmann has determined the heat of combustion of butter 

 fat as 9-231 calories per gramme, while Atwater found from 

 9-320 to 9-362 calories in three samples of butter, which appear 

 from the analytical results of Schweinitz and Emery to have 

 been of doubtful purity. 



The fat of milk is soluble in all hydrocarbons which are liquid 

 at the ordinary temperature, in their halogen derivatives, in 

 ether, carbon bisulphide, nitro -benzene, and acetone. It is 

 slightly soluble in alcohol and to a considerable extent in amyl 

 alcohol when cold, but in all proportions when hot. Glycerol, 

 when hot, dissolves it to a very small extent. It appears to mix 

 in all proportions with esters. Fatty acids have a limited solvent 

 effect, those of higher molecular weight dissolving more than 

 the lower homologues. Phenol also dissolves it to some extent. 

 On cooling a strong solution of the fat in any solvent, the portion 

 deposited has not the same composition as the original fat, but 

 is of the same nature as the solid portion obtained by slow cooling 

 of the melted fat. 



The molecular weight of the fat has been determined by Garelli 

 and Carcano by Raoult's cryoscopic method in benzene solution 

 to be from 696 to 716. That calculated from the amount of alkali 

 necessary for saponification is 720 to 740. 



