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 linseed 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 



