THE OIL CONTENT OF FLAXSEED 25 
be in a position to make their price on an oil-content basis, (2) the 
crusher could know within a short time the composition of the raw 
materials, and (3) the crushing plant could be more efficiently oper- 
ated, as frequent tests could be made at short intervals to determine 
just how much oil was being left in the cake by the presses. 
Early attempts have been made by different vegetable-oil chemists 
to simplify the ether-extraction method for making accurate oil 
determinations or to develop some rapid test which, although per- 
haps not so reliable so far as extreme accuracy is concerned, would 
give results sufficiently accurate for routine use in testing raw and 
finished products. As a practical matter only one of the proposed 
short methods has proven worth while. Reasons for lack of prac- 
tical success in the other tests include: (1) Time element not suffi- 
ciently reduced; (2) expense of making the test too great; (3) ac- 
curacy, as compared with the standard methods, not sufficient; or 
(4) method not simple enough for the average analyst to carry out. 
Of all the proposed methods, Wesson's (9) observation that he 
could measure the quantity of oil in cottonseed meal and meats by 
noting the change in the refractive index of a solvent known as 
halo wax (which, chemically speaking, is a substituted naphthalene) 
as it became diluted with cottonseed oil extracted from the sample of 
cottonseed under test, appeared to be the most worth while for con- 
sideration as a general method of study for the determining the 
oil content of many of the oil-bearing substances. Tests were, there- 
fore, made to see if the principle of the Wesson test could be applied 
so as to determine the oil content of flaxseed or linseed. 
Refractive index determinations were made on grade 1007 halowax 
oil and upon a composite sample of ether-extracted linseed oil at 
the grain research laboratory of the Bureau of Agricultural Eco- 
nomics. The refractive index of the halowax oil tested at 25° C. 
was 1.63354. The refractive index of the linseed oil tested was 
1.47878 at the same temperature. The difference in the two read- 
ings was 0.15476 — sufficient in size, it would seem, to make quantitive 
determinations of linseed oil in the presence of halowax oil possible. 
To note to what extent varying quantities of linseed oil would 
change the refractive index of halowax oil, percentage mixtures by 
weight of halowax oil and linseed oil were made and their refractive 
indices read at 25° C, with a new type of Abbee refractometer made 
in this country. This instrument could be accurately read to the 
fourth decimal place, and interpolation could be had to the fifth 
decimal place. 
The results of these tests are given in Table 18. It will be seen 
that as the percentage of linseed oil in the mixture changed, so 
likewise did the refractive index of the halowax oil change. The 
refractive index of the halowax oil without linseed oil present was 
1.63354; with 10.697 per cent of linseed oil present this reading 
changed to 1.61313; and when 14.237 per cent of linseed oil was 
present the refractive index had changed to 1.60636. On the other 
hand, the change in the refractive index of the halowax oil per 1 
per cent of linseed oil present was a constant, namely, 0.001906 per 
every per cent and fraction thereof of linseed oil present. 
