[dymond] elevator SCREENINGS 89 



The difficulty of grinding the screenings containing all of the weed 

 seeds is due to the hard flinty seed-coat of some, such as lamb's 

 quarters, and the very small size of others, as tumbling mustard. 

 These two seeds, it will be noticed, make up over 95 per cent of the 

 unground seeds in the feed cited above. Screenings carefully re- 

 cleaned over a screen with perforations one-fourteenth of an inch in 

 diameter to remove the black seeds may be satisfactorily ground by 

 an ordinary chopper. 



Uses for Black Seeds 



Many of the seeds making up the material known as "black 

 seeds" have a comparatively high content of oil and it has been 

 suggested that they might be used profitably in making oil. 



Brassica. The seeds of a number of varieties of Brassica campest- 

 ris are used in the manufacture of an oil to which the names rape or 

 colza are commonly applied.^ Rape oil is a semi-drying oil and is 

 characterized by a high viscosity and a saponification value lower 

 than that of any of the common oils of commerce. Rape oil was 

 formerly used in Europe and elsewhere to a very large extent as a 

 burning oil. The principal use of the oil at the present time is as a 

 lubricant; its high viscoscity, which can be increased by blowing hot 

 air through it, rendering it particularly suitable for this purpose. 

 Smaller quantities of rape oil are used for soft soap manufacture. In 

 India the oil is largely used as an edible oil, in fact, it is said to be the 

 chief oil for cooking purposes. In Europe refined rape oil is said to be 

 used as a "bread oil," i.e. for greasing the ends of loaves before baking. 

 Large quantities of rape oil are also used in steel-plate manufacture, 

 the heated steel plates being dipped in the oil in order to harden them. 

 Most of the varieties of Brassica campestris resemble Brassica nigra 

 in that they yield ethereal mustard oil to which the pungency of mus- 

 ard is due, but in much smaller quantities. 



The residues remaining after the expression or extraction of oil 

 from rape seed have a fairly high nutritive value. Rape-seed cake is 

 now used as a feeding stufï to a less extent than formerly. This is due 

 partly to disrepute owing to adulteration, especially to the fact that 

 rape cake is liable to contain mustard seed which produces injurious 

 efïects when fed to animals, owing to the presence of ethereal mustard 

 oil. The principal use of rape-seed cake is as a manure, generally 

 in the form of a meal from which almost all the oil has been extracted 

 by means of solvents. Rape-seed meal contains about 4-9 per cent of 

 nitrogen, 2-5 per cent of phosphoric acid, and 1 -5 per cent of potash. 



iBulI. Imp. Institute, 1915. 



