— 139 — 



oil, in some of their reactions, show a certain resemblance to pine-tar 

 oils and resin essences. Grimaldi, however, asserts that Halphen's reagent 

 (phenol in carbon tetrachloride in the presence of bromine vapours), 

 which he recommended some years ago 1 ), and which at that time was 

 used specially for the detection of resin spirit, can be readily employed 

 to differentiate between the three oils. Turpentine oils, he says, remain 

 uncoloured, or, at the most, assume a faint yellowish-pink tint under pro- 

 longed action of the bromine vapour, while pine-tar oils turn carmine- 

 pink to violet and resin spirit becomes yellow to malachite -green. 

 So far, however, this reaction has only been applied to the three oils 

 mentioned, not to their admixtures with petroleum, benzene, §c, and the 

 absence of the latter should therefore be first ascertained. For testing 

 varnishes to find out the character of their solvent, 25 to 30 g. of the 

 varnish is shaken up with 50 cc. water and distilled with steam. The 

 oil which has passed over, after being dried with calcium chloride, is 

 fractionated and the parts which have passed over up to 170° are examined 

 by the familiar process. 



In our opinion this method (assuming colour reactions to be of any 

 value whatsoever) does not admit of the identification beside each other 

 of several of the oils referred to. 



Among the physical methods proposed for testing turpentine oil the 

 one based upon the determination of the curves of miscibility, to which 

 we referred in our last Report 2 ), has since then been recommended for 

 the same purpose by Louise 3 ), who found that the addition of even so 

 small a proportion as 5°/o white spirit gives rise to a perceptible deviation 

 from the normal course of the curve, and that when 20°/o white spirit 

 is added, this deviation is very largely increased. The curves of resin 

 oil also differed greatly from those of pure turpentine oil, but were on 

 the opposite side of the ordinates as compared with the white spirit curve. 

 Vezes 4 ), in commenting upon Louise's suggestions, points out that the 

 method based upon the determination of the curves of admixture was 

 first applied to turpentine oil in his (Vezes') laboratory by Queysanne, and 

 calls attention to a series of inexactitudes in Louise's paper. For instance, 

 the fact must be taken into account that the various kinds of white spirit 

 give different curves and also that the presence in the turpentine oil of 

 resin acids and other products of resin distillation 5 ) affects the temperature 

 coordinates of the curve, owing to the basic properties of the solvent, 

 aniline. Where 5°/o neutral resin oil is present the extent of this influence 



!) Comp. Report April 1908, 105. 



2 ) Report April 1910, 116. 



3 ) Compt. rend. 150 (1910), 526. 



4 ) Ibidem 698. 



5 ) Comp. Report October 1909, 121. 



