— i3i — 



its chemical and physical properties from pure pinene; its constants are 

 as follows: b. p. 152 to 153,5°; ^000,8598; n D20O i,47 2 99; Md — 47> 2 °- 

 Firpene hydrochloride melted after repeated recrystallisation from alcohol 

 at 130 to 13 1 °, and has consequently the same melting point as pinene 

 hydrochloride according to Long. It is, however, more volatile and 

 more readily soluble than the latter, and has a somewhat different odour. 

 But the principal difference lies in its totally different behaviour towards 

 chlorine. Whereas pinene hydrochloride shows no inclination to form 

 a dichlorohydrochloride, firpene hydrochloride yields such a product; 

 on the other hand, no crystalline higher chlorides could be produced. 

 The hydrobromide of firpene melts at 102°, pinene hydrobromide 

 at 90°. The feathery crystals of the former are very volatile, and 

 soluble in almost all organic solvents. 



Pinene and firpene also behave differently towards nitrosylchloride. 

 The former, as is well known, yields without difficulty a beautifully 

 crystallising nitrosochloride. From firpene, however, no crystallising 

 nitrosochloride could be obtained with nitrosylchloride. This reaction 

 is clearly the characteristic distinguishing feature between the two 

 terpenes, 



Dipentene. The boiling point of dipentene had long ago been 

 given by Wall a ch 1 ) as 178 to 180°. Semmler 2 ) attributes this high 

 boiling point to the presence of terpinene, and is of opinion that under 

 all circumstances, according to every experience, dipentene must boil 

 at the same point where active limonene boils, i. e. 174 to 175°. 

 Wallach 3 ) replies to this, that he has never stated that he had obtained 

 forthwith pure dipentene, and he then indicates a detailed method for 

 the production and purification, which yields the purest dipentene 

 which it has up to the present been possible to produce. It boils 

 from 177 to 1 78°, that is to say about 2° higher than active limonene, 

 or inactive limonene obtained by mixing the active bodies. For the 

 purpose of comparison the tetrabromides of dipentene and of inactive 

 limonene were employed. From 10 g. of the former 10 g. bromide 

 were obtained, from 10 g. of the latter 8,5 g. bromide. In these 

 8,5 g. the bromide of any other terpene could not be detected. From 

 the higher - boiling portions (180 to 185°) of crude dipentene also, 

 only dipentene tetrabromide could be obtained, and no terpinolene- 

 bromide. No fraction of the crude dipentene used (50 g.) gave the 

 terpinene reaction. On the strength of this experiment Wallach 

 concludes that in the dipentene fraction (b. p. 177 to 17 8°) a terpene 

 which can be detected by the reactions hitherto known could hardly be 



') Liebig's Annalen 227 (1885), 239, 301; 239 (1887), 12. 



2 ) Semmler, The Volatile Oils, vol. II, 309; Berl. Berichte 39 (1906), 4427. 



3 ) Berl. Berichte 4:0 (1907), 600. 



9* 



