( 5 ) 
to recover all the oil in the seed, whereas by pressure 
alone it is rarely possible to obtain more than 90 
per cent, of the total oil contfent. 
In general, it may be said that the method of ex- 
pression is invariably followed if the cake is to be 
used as a feeding stuff, as the small amount of oil 
therein forms a valuable constituent. In the case 
of mouldy or damaged seed material, where the 
cake could not be used for this purpose, or where 
the cake cannot be employed on account of some 
poisonous principle, the solvent extraction process 
is to be preferred. 
Application and Uses . — It would be difficult to 
enumerate all the uses of oils, but among the 
chief are the applications which they find in the 
manufacture of butter substitutes (margarine) and 
other preparations for edible purposes, soaps and 
candles, paints and varnishes, linoleum, leather 
and lubricants. To a certain extent the industrial 
application of an oil depends on whether it belongs 
to the drying class of oils. The surfaces of such 
oils, when exposed to air, film over or solidify; and 
this property, which is known as drying, is taken 
into account when selecting an oil for utilisation in 
the manufacture of paints and varnishes, the film 
produced forming the protective coating on the 
material treated. In all these applications, except 
in the case of soap and candles, the oil must be free 
from a large excess of fatty acids ; otherwise it must 
undergo a preliminary refining process or be used 
as soap or candle stock, in which case the presence 
of free fatty acid makes little difference. 
As stated above, the oil cake or meal remaining 
after extraction forms a valuable bye-product, either 
as a cattle food or fertiliser. It is more profitable 
