Mr Davidson on the Adulteration of Fixed Oils. 255 



gow at that period, and which rendered them inferior in the 

 manufacture of soap. I found, however, that the acid nitrate 

 of mercury gave no indication whatever"; for its action on 

 linseed oil is very similar to its action on these fish-oils, viz. 

 whale, cod, and pale seal oils. 



The following experiments were then made in order to dis- 

 cover some test for the presence of the ordinary commercial 

 linseed oil. Equal bulks of alcohol of sp. gr. 0.815 and lin- 

 seed oil were mixed together in a phial and well agitated for 

 a few minutes, the alcohol separated in a short time from the 

 oil, and acquired a gi'eenish-yellow colour of considerable in- 

 tensity. In order to ascertain if other fixed oils gave any in- 

 dications of a similar nature, I submitted the following, pro- 

 cured from the most respectable sources, to the same treat- 

 ment ; viz. four varieties of olive oil, Gallipoli, Levant, Cala- 

 bria, and Sicily, also rape oil, almond oil, sperm oil, dolphin 

 oil, whale oil, cod oil, and pale seal oil. None of these, how- 

 ever, communicated any perceptible colour to the alcohol ; but 

 10 per cent, of linseed oil, added to whale oil, gave a very per- 

 ceptible greenish-yellow tint to the alcohol that was made to 

 act upon it. This method I have used practically, in one or 

 two instances, for detecting the adulteration of whale oil with 

 linseed oil. It is proper to state, that the linseed oil employ- 

 ed in these experiments, was the brownish-yellow variety used 

 universally for commercial purposes in Scotland, and which is 

 always employed for the adulteration of fish-oils. There is 

 also a pale yellow variety of linseed oil, which is very rarely 

 to be met with, and which is only used in very small quanti- 

 ties, but which does not give the same precise indications with 

 alcohol as the ])rownish-yellow oil. 



I lately, however, met with a specimen of whale oil, repre- 

 sented to 1)0 genuine,* that communicated a slightly brownish 

 tint to alcohol. 



71 West Nile Street, Gla.sgow, !!)(/* April 18.'J8. 



* It may be proper to state tliat the alcohol omploycd in the specimens 

 sonttf) the Soci(!ty of Arts, was rectified with sub-carbonate of pota.ss without 

 •listlllation, and that, in consoquenco, the oil has a. milky iippearnnce. In all 

 the former cxperiiucnts, the alcohol ha4becn afterwardu distilled. 



