DETECTION OF ADULTERATIONS. 323 



wrong; but, on the other hand, adulterating substances 

 may be used which fail to give any indications with 

 potass. While attention to these points will enable the 

 observer in many instances to detect the inferiority of an 

 oil-cake, it is no unfrequent occurrence to find specimens 

 in which the eye detects nothing amiss, but which ana- 

 lysis shows to be inferior. Not long since I examined 

 a sample which was particularly well pressed, was in 

 remarkably neat cakes, and showed to the naked eye not 

 the slightest appearance of foreign seeds, but analysis 

 proved its composition to be as follows : 



Albuminous compounds, 21*35 



Oil, 9-01 



Mucilage, sugar, &c., 39'96 



Fibre, 9'36 



Ash (mineral matter), 9 '51 



Water, 10-81 



100-00 



The small proportion both of oil and albuminous com- 

 pounds in this sample is remarkable, the latter being as 

 much as 7 per cent, below the average. It was afterwards 

 so far explained by information I received, that, at the 

 mill where it was made, it was the practice to mix with 

 the linseed a small quantity of bran or ' thirds/ not as 

 an adulteration, but because it had been found that the 

 seeds pressed better and gave a larger yield of oil. On 

 examination with the microscope, I found that it did con- 

 tain some granules of starch, apparently of wheat, but the 

 quantity was not large; and I can scarcely imagine that 

 this was the sole cause of the small proportion of albu- 

 minous compounds." 



In reference to the chemical investigation of linseed- 

 cake, Dr. Voelcker tells us that the ash which remains 

 behind on burning should not create much effervescence 

 when mixed with an acid. If a strong action takes place, 



