- 168 — 



According to Sievers the reactions which take place at room-temperature 

 are due to simple absorption, whereas at high temperatures the acid un- 

 questionably attacks the molecule. The same experiments were repeated 

 at atmospheric pressure by heating in a reflux condenser. In both 

 cases the ester value was found to be much higher than in the previous 

 experiments. A few of the values determined by Sievers are given in 

 the table (II) (p. 167) below. 



The findings of Sievers described above made it appear desirable to 

 determine the extent to which acetic anhydride reacts with pinene and 

 limonene under experimental conditions similar to those observed in 

 acetylating essential oils. Several samples of freshly purified and recti- 

 fied terpenes, when treated in this manner, gave an ester value after 

 acetylation of not more than 1,8 = 0,5 °/o Ci Hi 8 O, a value which is negli- 

 gible in practice, and is therefore without effect in the alcohol-determi- 

 nation of essential oils. The values are slightly higher with impure hydro- 

 carbons, or hydrocarbons which are somewhat resinified as a result of 

 prolonged keeping. Where such was the case we observed an ester 

 value after acetylation ranging, according to the age of the sample, up to 

 15 = 4,2 °/o CioHisO; a pinene which was more than four years old 

 registering as much as 38,2= 10,8°/o Ci Hi 8 O. 



Camphene. K. Auwers 1 ) in a paper on the constitution of camphene, 

 refers to the recent work of Aschan and Lipp 2 ) on this hydrocarbon. The 

 progress attained by the researches embodied in that work lies in the 

 proof which has been afforded that, contrary to the opinions of Moycho 

 and Zienkowsky, the camphenes of different origin are in their essentials 

 of a uniform character and represent one and the same hydrocarbon. In 

 the present state of our knowledge however it appears to be impossible 

 to draw positive conclusions with regard to the constitution of the hydro- 

 carbon from the chemical conversions of camphene alftne. But in the 

 case under review it would appear that the spectrochemical behaviour 

 scarcely leaves room for doubt as to the group of hydroaromatic com- 

 pounds to which the hydrocarbon belongs. To obtain useful results it is 

 necessary, when calculating the spectrochemical data, to compare the 

 latter with water at 4°. In comparing the statements of Wallach, Bruhl, 

 Eijkman, and Helle on the refraction and density of camphene, it will be 

 found that they have all been estimated at temperatures ranging froo* 

 40 to 78°, but the estimated values may be converted with sufficient ac- 

 curacy to 50°. Having done this, Auwers ascertained the mean of the cam- 

 phene-values found by the above-mentioned authors to be M a 43,73 and 



*) Liebigs Annalen 387 (1912), 240. 



2) Comp. Report April 1911, 188; October 1911, 132, 135. 



