6 BULLETIN 655, U. S. DEPARTMENT OF AGRICULTURE. 
chemical constants. Ether extractions were made by means of the 
customary Soxhlet extractors, while a small laboratory hydraulic 
press served for the cold expression of the oil. The yields of oil 
given in all cases represent ether-extracted oils, whereas all physical 
and chemical properties were determined upon cold-pressed oils. 
It must be borne in mind that these cold-pressed samples differ 
from ordinary commercial raw linseed oils, being obtained under 
entirely different conditions. The results obtained are therefore 
comparable with each other, but not with commercial linseed oils. 
The color was carefully noted in each case. Considerable diversity 
appeared and the colors are described as well as possible in order 
to bring out the existing differences. 
The specific gravity and the refractive index, being affected by 
the composition of the oils, were carefully determined. Both of 
these constants bear a certain relationship to the composition of 
the oil. 
Table II was prepared to show the similarities and differences 
in yield and physical properties of the various oils examined. The 
yield of oil and physical properties are arranged according to the 
stations at which the several varieties of flax were grown. Each 
Cereal Investigations number of flax grown at any station is given, 
together with the yield of oil during the two years. This arrange- 
ment permits a comparison of the varieties grown at each station 
during the two successive seasons. 
By a careful study of Table II it will be seen that the samples of 
flax bearing Cereal Investigations numbers grown at each station 
during either of the two years vary considerably in yield of oil. This 
variation is apparent at each of the stations. Since each of the 
numbers represents a different variety, the differences in the yield of 
oil may be attributed to the varieties. When the same variety as 
grown at widely separated stations shows differences in yield of oil 
it is probable that climatic and soil conditions play an important 
part. 
In comparing the Cereal Investigations numbers of any one station 
during the two years, the yields of oil in many cases are distinctly 
comparable. While not constant, a certain degree of constancy is 
noticeable among them. 
In order to make a better comparison of the Cereal Investigations 
numbers, not only at each station but at all the stations, the average 
oil yields were calculated and are included in Table II. A glance 
at the average yield of oil from the various Cereal Investigations 
numbers discloses those producing the highest and lowest yields at 
each station. It is noticed that Nos. 3 and 19 occupy a high position 
with regard to oil content, while Nos. 12 and 13 are usually low. 
The stations producing the highest and lowest oil yields are also 
clearly indicated in Table II. 
