CHAP. xn. PURITY OF LINSEED CAKES. 201 



there are occasions when a more perfect examination is required, and 

 there are other tests of a more chemical character which I have noticed, 

 but as they are more difficult of manipulation, I thought it hest to 

 remain silent respecting them, pointing out only the simple test which 

 I have given, one that is really very useful, and can be handled by 

 every man. I have given you a brief outline of the method which, 

 after all, I am myself frequently obliged to follow, in addition to the 

 chemical examination to which I submit the cakes when sent to me 

 for that purpose." 



An instructive article on the purity of linseed cakes, communicated 

 by Dr. J. A. Voelcker to Morton's "Farmers' Almanac," suggests 

 some modification of the foregoing. From it the following details are 

 taken : 



" It is unfortunately the case with linseed cakes, that much which in 

 the crude state would stand out boldry by its different appearance, may 

 in the finely ground and crushed state be only too readily made to lose 

 its distinctive character and to supply the place of a more expensive 

 article. Although here and there a so-called 'pure ' cake may be so glaring 

 by the admixture of what is not linseed as to lead to suspicion in the 

 minds of even those who are not experts, by reason, it may be, of a 

 bad or bitter taste, a pungent smell, the presence of a quantity of black 

 husk, or even sometimes by a believed grittiness, these are but the 

 exceptions, and the vast majority would go unnoticed, for the}^ are such 

 as only the practised skill and the special appliances and methods of the 

 expert can detect. And what are these impurities, and how may they 

 be detected? So formidable is the list of them that their description 

 alone would involve space far greater than is at my present disposal. 

 Moreover, the work has already been so fully and ably done by the late 

 Dr. Voelcker in a paper (from which our page 200 is quoted) entitled 

 'Pure and Mixed Linseed Cakes' ('Journal E. A. S. E.,' 2nd series, 

 vol. ix., part 1), that it would be needless to repeat it. I wish rather 

 to confine myself to what may be called the later, most flagrant, and 

 most fashionable developments of the art of ' mixing.' 



" Prominent of late amongst adulterants has been rape-seed from 

 which the oil has been for the most part extracted by chemical means. 

 An analysis of this material is given below : 



Moisture . 7 "98 



Oil 5-54 



'Albuminous compounds (flesh-forming matters) . . . 33 '12 



Mucilage, digestible fibre, &c. . . . . . . 32 - 07 



Woody fibre 13-61 



fMineral matter (ash) 7 '68 



100-00 



'Containing nitrogen 5 '30 



+Including sand 2 '44 



" This material seems to have found special favour, it being offered 

 for sale with the strong recommendation that it is impossible to detect 

 it by analysis. So popular has this particular adulterant become, that 

 its market value, starting\ from 20s. or so per ton, has gradually 

 increased up to 4Z. per torn After procuring some of this material 



