8 BULLETIN 655, U. S. DEPARTMENT OF AGRICULTURE. 



The specific gravity is a property which bears a certain relation- 

 ship to the composition and hence is more closely related to the 

 quality of the oils. Table II shows considerable variation among 

 the Cereal Investigations numbers at any station during either season. 

 When compared according to stations, the specific gravity shows a 

 tendency to be high or low in several locations during both seasons. 

 When grouped and averaged according to the stations at which 

 the flax was grown and according to the Cereal Investigations 

 numbers, some striking comparisons, which will be discussed in 

 later pages, are made possible. 



In Table II the index of refraction is given for the various oils, 

 along with the specific gravity, as a physical property which is 

 subject to similar variation, according to the composition of the 

 oils. It will be noted that in practically all cases where the specific 

 gravity is high the index of refraction is also high. 



The acid, saponification, and iodin values ' of the oils from the 

 several stations were determined, together with the drying tests, 

 arid the results are arranged for comparison in Table III. 



In considering the acid value of the Unseed oils it will be seen that 

 there is not only considerable variation in the oils from the various 

 Cereal Investigations numbers during each of the seasons at each 

 station, but the same number at other stations shows similar differ- 

 ences. The differences among the numbers at any station during 

 either year may be due to difference in the type and character of the 

 plants, but differences shown by the same number at different sta- 

 tions can probably be attributed to varying conditions of the har- 

 vested seed, the weather conditions during harvest, and the method 

 of harvesting and storing. 



No definite relationship seems to exist in the acid values of various 

 samples at any one station during the two years. Comparison of the 

 average acidity of samples grown at the various stations during the 

 two years shows the variability of the acid values. In most cases the 

 acidity of the oils from the 1914 samples was much higher than from 

 the 1915 samples. 



The saponification value, which represents the sum total of the free 

 acids and glyceryl esters in the oils, will be seen to bear a close rela- 

 tionship to the acid values. The average of the saponification values 

 of the oils from each station was higher during 1914 than during 1915, 

 which is likewise true of the average acid value of the same oils. 



In considering the iodin values of the several samples it will be 

 seen that there is considerable individual variation among the several 



1 Determinations of the chemical constants were made in accordance with the official and provisional 

 method of analysis, Bureau of Chemistry Bulletin Xo. 107 (revised), 1910. The iodin values were obtained 

 by means of the Iliibl method, 4 hours beincr allowed in every case for the absorption of iodin. Complete 

 iodin absorption doubtless 'lid not take place in the above time. The results, however, serve well for 

 the comparative purposes for which they are used. 



