Commercial and scientific notes on essential oils. 47 



literature on the examination of oil of turpentine. His own experiments lead the 

 author to the conclusion that the oxidation method with mercury acetate according 

 to Tausz 1 ), the bromination method according to Allina-Salvaterra 2 ), and the iodine- 

 addition method as modified by the author will answer their purpose and will mutually 

 supplement one another. With pine tar oil, about 10 per cent, will separate from the 

 steam distillate by the mercury acetate method. Since such a separation does not 

 occur with the other methods, any addition of that oil can be discovered by mul- 

 tiplying the difference obtained in the separations according to Tausz and to Allina- 

 Salvaterra by 10. In the presence ot tetrahydronaphthalene this pine tar oil determination 

 is not possible, since tetralin reacts partly with the halogen. 



A. Allina and H. Salvaterra 3 ) have also published an extensive research on the 

 determination of light petroleum in oil of turpentine. The methods of H. Herzfeld and 

 }. Marcusson 4 ), so far applied for this determination in oil of turpentine and in pine 

 tar oils, are based upon a violent destruction of the terpene hydrocarbons and do not 

 always give satisfactory results. The method recommended by Allina and Salvaterra 

 renders it possible to separate oil of turpentine and light petroleum and to determine 

 the light petroleum contents without any' destructive reaction. According to this 

 method the physical properties of the sample are so altered by the bromination of 

 the oil that only the non-brominated light petroleum will pass over in the steam 

 distillation and can then easily be determined. 



The authors recommend a few preliminary tests which are based upon the following 

 observations: — (1) rise of temperature of the sample on addition of sulphuric acid of 

 the concentration 2:1 (2 -j- 1 ?) ; (2) determination of the expansion coefficient; (3) increase 

 in' the specific gravity by the bromination; (4) determination of the quantity of bromine 

 taken up, by means of the weight of hydrogen bromide required for the bromination. 



These preliminary tests do not, it is true, admit of an exact determination of the 

 petrolether percentage, but they are valuable for the recognition of the adulterations 

 and also for the rapid distinction between oil of turpentine and so-called patent oil 

 of turpentine, such as the Customs Authorities require, or for the distinction between 

 oil of turpentine and pine tar oil. 



In the bromination of oil of turpentine no analytical value must be attached to 

 the absolute quantity of the bromine consumed even when the analyses are performed 

 under constant conditions, because the reactions may be extremely complex and involve 

 addition and substitution and breaking-up of the ring. 



On the other hand it is a valuable fact that the boiling points of all the terpenes 

 are raised by the bromination so that a separation of the light petroleum by distillation 

 becomes easily possible. The bromination is best effected by bromine in statu nascendi.. 

 by the decomposition of bromic acid by means of hydrogen bromide. In this reaction 

 pine tar oils and oils of turpentine do not behave in the same way, because the 

 attack by bromine of the pine tar oil is much more sluggish than in the case of the 

 oil of turpentine. Bromination by hypobromous acid does not offer any advantage 

 over the just described method. 



As regards the determination of oil of turpentine in the oil of the Siberian fir, 

 J. W. Howorth 3 ) describes a method, according to which he recognises adulteration 

 by the oxidation of oil by means of air under addition of j^ potassium iodide solution 



*) Chem. Ztg. 42 (1918), 349. — 2 ) See next reference. — 3 ) Chem. Ztg. U (1920), 673 and 697. 

 *) Cf. Report April 1910, 114. — 5 ) Pharmaceutical Journ. 101 (1920), 345. 



