103 Mr. F. C. Calvert on the Adulteration of Oils. 



their application to enable me to obtain satisfactory results. To 

 this class belong the delicate process recommended by M. F. 

 Boudet, principally for the detection of drying oils in olive by 

 the action of hyponitric acid; and M. Rousseau's diagometer, 

 which is based on the very inferior conducting power of olive oil 

 as compared with that of the others. 



For distinguishing one class of oils from another we have 

 M. Faure's method, which consists in the brown or black tinge 

 which fish oils exclusively assume when a stream of chlorine gas 

 is passed through them ; and M. Maumeue's, by which the drying 

 oils may be distinguished from the non-drying ones, owing to the 

 fact that the latter, when mixed with strong sulphuric acid, give 

 rise to a much higher temperature ; but although M. Fehling 

 has endeavoured lately to give more precision to M. Maumene's 

 researches, it is far from being satisfactory. 



There are other processes the characters of which arc not suf- 

 ficiently distinct to be employed with any degree of certainty ; 

 such is M. Faure's, which consists in adding a given quantity of 

 caustic ammonia to oils, and noticing after they have been mixed 

 the peculiar appearance which the white or yellow thick fluids 

 present. The same may be said of the process proposed by 

 M. Heideni'eich with monohydrated sulphuric acid, or that of 

 M. Diesel with concentrated nitric acid ; for the chemical actions 

 are so violent, that the characteristic colorations, which are at 

 first produced, rapidly disappear in consequence of the destruc- 

 tion of the oils. 



These facts induced me to examine what would be the action, 

 on oils, of the above acids when diluted, and the satisfactory 

 results obtained are described in this paper. 



The marked colorations produced may be considered as derived 

 from two distinct chemical actions: — first. They appear due to 

 certain foreign matters which are dissolved in the oils, and which 

 existed in the substance from which they were extracted; 

 secondly : The diluted acids have probably an action on the 

 component parts of the oils themselves ; for if caustic soda be 

 added to oils so acted upon, a different result is obtained than 

 when no acid has been previously applied ; this fact being cleai'ly 

 illustrated with French nut oil, as it gives a semi-saponified fluid 

 mass when caustic soda of spec. grav. 1"340 is alone mixed with 

 it, and a fibrous mass when treated by dilute nitric acid previous 

 to the addition of the alkali. 



It may be interesting here to remark, that fish oils have pre- 

 sented distinct reactions from other animal or vegetable oils; 

 consequently, in my opinion, not only has cod-liver oil a different 

 composition to that of other oils, as shown by the researches of 

 M. Winckler, but also probably sperm and seal oils. 



