— 138 — 



to serve as a means of distinguishing between them. In the result the 

 authors recommend their method, which has been specially worked out 

 for pure turpentine oils and their sophistication with petroleum and ben- 

 zene (not with sangajol $c.) on the ground of its accuracy and the rapi- 

 dity with which it can be carried out. 



So far the only method applicable to the detection of petroleum 

 distillates in turpentine oil has been that of Burton 1 ), but Nicolardot and 

 Clement 2 ) propose to carry out this determination by converting the con- 

 stituents of turpentine oil into non-volatile compounds by the action of 

 oxidising agents and then carrying off the unattacked oils by steam. Acetic 

 acid is recommended as a convenient, stable, and cheap solvent for the 

 oil. Chromic acid, nitric acid and the two acetates of mercury were 

 used as oxidising agents. Pure oils gave a volatile residue of 4°/o by 

 volume with chromic acid and 7°/o by volume with nitric acid; any ex- 

 cess on these figures indicates a corresponding sophistication. Pure 

 oils gave 10°/o resinous residue with nitric acid; if this percentage is ex- 

 ceeded excessive resin-content of the oils is indicated, due either to age, 

 imperfect distillation, or the addition of resin. Of the two mercury acetates 

 the authors prefer mercurous acetate, as against the mercuric salt used by 

 Balbiano and his collaborators. In conclusion the following method of 

 determination is recommended: Dissolve 70 g. mercurous acetate in 150 cc. 

 acetic acid, pour 50 cc. of the oil to be examined into the flask and heat 

 the whole for 30 minutes on the water bath, using a reflux condenser. 

 Then distil with steam and ascertain the volume of the oil which 

 has passed over. Pure turpentine oil is completely oxidised by the agent 

 mentioned without leaving any volatile residue; any volatile portion, 

 therefore, indicates adulteration. White spirit is not wholly driven over, 

 as a portion of this substance is attacked by the acetates of mercury, 

 but the proportion in this case is only very small. 



Of the various colour-reactions (reaction with pieces of caustic potash, 

 with nitrazol for the detection of phenols, with sulphurous acid, and others), 

 which have been recommended to differentiate between those three re- 

 latively closely-allied substances, turpentine oil, pine-tar oil, and resin 

 spirit ("turpentine essence") of which the two latter are often added to 

 the first on account of their resemblance to it, hardly any one, in Gri- 

 maldiV) opinion, is practicable. None of the various turpentine oils, pine- 

 tar oils and resin essences showed any characteristic behaviour towards 

 the said reagents; in fact, pine-tar oils and resin essences generally react 

 either in the same way or closely alike, and many samples of turpentine 



x ) Compare the preceding statements. 



2 ) Bull. Soc. chim. IV. 7 (1910), 173. 



3 ) Chem. Ztg. 34 (1910), 721. 



