INFLUENCE ON LINSEED OIL OF SOURCE OF FLAX, ETC. 5 
this property as carefully as possible. The specific gravity and the 
refractive index, which have much significance as regards the gen- 
eral composition of the oils, were readily determined. 
The chemical properties are perhaps most important from the 
standpoint of the composition of the oils. The acid, saponification, 
and iodin values are the most important chemical constants. The 
acid value of the linseed oils is affected by a number of conditions. 
Factors such as rain or moisture during harvest and the storing 
of the moist flax after harvest, which would tend to produce mold- 
ing of the seed, will modify considerably the acid value of the oil. 
The saponification value representing the sum of the acid and ester 
values is a combined measure of the free acids and glyceryl esters 
contained in the oil. 
Linseed oil consists for the most part of glyceryl esters of lino- 
leic and linolic acids. These unsaturated fatty acids possess the 
property of absorbing iodin. This property is known as the iodin 
value and is perhaps the most important of the chemical constants. 
The iodin value is a direct criterion of the proportion of these fatty 
acids present in the oil, and since these acids determine the drying 
property of linseed oil the iodin value becomes an index of this 
property. 
The usefulness of linseed oil in the industries is based upon the 
property of the oil to dry to a tough elastic film when exposed in 
thin layers to the air. This oil is a typical example of a class of fatty 
oils known as drying oils. Oils of this character are composed 
largely of glycerids of unsaturated fatty acids which possess the 
property of absorbing oxygen when exposed to the air. The absorp- 
tion of oxygen by linseed oil alters its composition and is accompanied 
by the formation of a compound known as linoxyn, which consti- 
tutes the tough elastic skin so familiar when the oil is allowed to 
dry. The usefulness of Unseed oil as a protective coating is due 
entirely to the formation of the compound linoxyn, which is resist- 
ant to the effects of heat and moisture of the outside elements to 
a remarkable degree. 
Coincident with the absorption of oxygen there occurs an increase 
in the weight of the oil, and the more rapid the increase in weight 
the greater is the rapidity of drying, and vice versa. Advantage 
was taken of this property in order to determine the relative drying 
value of the various oils under consideration. 
YIELD AND PHYSICAL PROPERTIES OF THE OILS. 
Two methods were used for the extraction of the flax samples, 
namely, ether extraction and cold expression. The former method 
was applied to determine the actual yield of oil in the seeds, while 
the method of cold expression was employed to obtain working 
samples of the various oils for the determination of the physical and 
