8 BULLETIN 655, U. S. DEPARTMENT OP 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 l of the oils from the 
several stations were determined, together with the drying tests, 
and the results are arranged for comparison in Table III. 
In considering the acid value of the linseed 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 No. 107 (revised), 1910. The iodin values were obtained 
by means of the Hiibl method, 4 hours being allowed in every case for the absorption of iodin. Complete 
iodin absorption doubtless did not take place in the above time. The results, however, serve well for 
the comparative purposes for which they are used. 
