XIX. METHODS FOE THE ANALYSIS OF EDIBLE FATS AND OILS. 



1. Preparation of Sample. Provisional. 



Melt the solid fats and filter by means of a hot-water funnel or similar 

 apparatus. Make the different determinations on samples of this melted homo- 

 geneous mass. Filter oils that are not clear. Oil and fat should always be 

 kept in a cool place, otherwise they will soon become rancid, which will affect 

 more or less the physical and chemical constants. 



2. Specific Gravity, 

 (a) DETERMINATION AT 15.5 C. PROVISIONAL. 



Determine the specific gravity of oils at 15.5 C., by the use of a pycnometer 

 Westphal balance, or accurately graduated hydrometer. 6 



If determined at room temperature, the following formula may be used to 

 calculate the specific gravity at 15.5 C. : c 



G =G' + 0.00064 (T 15.5 C.). 



G = sp. gr. at 15.5. 



G' = sp. gr. at T. 



0.00064 = mean correction for 1 C. 



This is only approximately correct, as the correction varies for different 

 oils, but will satisfy ordinary requirements. If a higher degree of accuracy 

 be desired, the factors given in the following table may be employed, but to 

 obtain the best results the determination must be made at standard temperature. 



Factors for calculating specific gravity of oils.* 



The following table gives correction for solid fats: 



Factors for calculating specific gravity of solid fats.e 



"Crampton, U. S. Dept. Agr., Division of Chemistry, Bui.- 13, Part 4, p. 438. 



b Accurately made hydrometers reading from 0.900 to 0.940 sp. gr. at 15.5 C., will 

 satisfy every requirement of accuracy and speed.. 



c Allen, Commercial Organic Analysis, 3d. ed., 2 (1) : 33; Winton, Conn. Agr. Exper. 

 Stat. Kept, 1900, Part 2, p. 149. 



* Allen, Commercial Organic Analysis, 3d ed., 2 (1) : 33. 



Ibid., p. 32. 



129 



