16 BULLETIN 952, U. S. DEPARTMENT OF AGRICULTURE. 
hopper, where a horizontal rotating screw carries the charge forward 
and subjects it to great pressure by discharging it over a cone in the 
throat of the horizontal barrel containing the charge and screw. The 
oil drips from openings in the barrel and the cake or chips are dis- 
charged from the throat. 
Owing to the comparatively low oil content of the seed (13 per 
cent) and also to the very hard seed coat, which tends to cause exces- 
sive wear on the expeller, it is desirable that the seed be first decorti- 
cated. Thus, a large part of the hard hulls may be removed and the 
oil content of the kernels be more readily obtained. The resulting 
cake has also a much lower fiber content than if the whole seeds were 
passed through the expeller. 
In the laboratory a successful decortication was effected by passing 
the seed through a vertical-plate mill set for medium to coarse grind- 
ing. The ground mass of seeds was then passed through a rotary 
sifter (of the flour-sifter type) fitted with No. 20 wire mesh. This 
produced a separation of the coarser particles of the shells or hulls 
from the finer meaty portion of the seeds. The hulls were found to 
constitute 44 per cent of the seeds and the kernels with some of the 
finer particles of shells 56 per cent. The hulls showed an oil content 
of 4.07 per cent and the kernels 19.9 per cent. 
The kernels were now in condition to permit the oil to be readily 
extracted, and the shells were in such small quantity as to have only 
a minimum wearing effect upon the expeller. The yield ef oil 
obtained from the kernels was about 14.5 per cent. This oil was 
of a dark-green color and had a strong nutlike odor and taste. 
After being refined it was straw colored with a shght greenish tint 
and pleasant bland taste and smell. 
Solvent extraction of any oleaginous material depends upon the 
solubility of the oil in some volatile solvent, such as benzol. When 
dry ground grape seeds are treated with a warm benzol solution the 
latter dissolves the oil, which is then separated from the solution by 
distillation of the solvent. ‘The recovery of the solvent from the 
solution is thus effected, enabling it to be used repeatedly. The 
extracted residue is treated with steam to remove the traces of 
benzol. By this method from 11 to 12 per cent of oil may be obtained. 
Such a solvent-extraction plant is shown in figure 10. 
The crude grape-seed oil which was obtained by this method was 
refined and yielded an oil equal in quality to that obtained by 
pressure. 
It will readily be recognized that each of these methods has both 
advantages and disadvantages. The solvent-extraction method pro- 
duces a greater total yield of oil than the pressure method, but the 
oil cake resulting from the pressure method possesses valuable stock- 
feeding qualities which would enable it to be sold to better advantage 
