- 84 - 
The property which many terpenes possess of forming xanthogenic 
acid esters, which on being heated yield the original hydrocarbon, 
lends itself, according to Tschugaeff, especially to the isolation of 
terpenes and the production of those bodies in the pure state, as, in 
consequence of the absence of acids and alkalis, a rearrangement and 
formation of isomeric hydrocarbons is improbable. 
Kondakow^), however, starting from anomalies which had been 
observed in regenerating bornylene from the xanthogenic acid ester, 
concluded that by this method no uniform bornylene is obtained, but 
that a portion passes over into camphene, as, contrary to pure bornylene, 
it yielded an ester w^hen boiled with zinc chloride and glacial acetic 
acid, and also, when treated with hydrochloric acid gas in a solution 
of petroleum ether and of glacial acetic acid, yielded a mixture of the 
hydrochlorides of bornylene and pinene. Kondakow and Skworzow^) 
observed similar conditions when regenerating thujene according to 
Tschugaeff's method. The crude hydrocarbon boiled within very 
wide limits, and could be separated by methodical fractionating into 
portions of widely differing rotatory powers. Tschugaeff^) does not 
accept Kondakow's view that the high decomposition - temperature 
of the bornyl and thujyl xanthogenates favours the formation of 
isomeric forms, and he attributes the formation of the camphene or 
of the isobomyl acetate from the bornylene, to the esterification method 
employed. In opposition to these statements Kondakow maintains 
his opinion, and he points out many discrepancies in Tschugaeff's 
arguments. The controversy appears to show- that the production of 
terpene hydrocarbons by the xanthogenate method, which at first 
appeared quite plain, does not lead to the uniform products which its 
discoverer assumed. 
Pinene. The behaviour of pinene towards bromine, which had 
already been examined repeatedly, has once more been studied by 
P. Genvresse and P. Faivre^). Wallach^) as long ago as 1891 
had conclusively settled the question of the addition-capacity of pinene 
for bromine, by converting the pinene in the then still unknown crystal- 
lised pinene dibromide of the melting point 169° to 170°. This 
reaction, conducted by Wallach in a dry solvent, proved the divalent 
character of -pinene as compared with halogens. Genvresse and 
Faivre arrived at the same result when they allowed bromine 
^) Journ. f. prakt. Chemie II. 67 {1903), 280. 
2) Journ. f. prakt. Chemie II. 67 (1903), 573. 
^) Report of the proceedings of the Russian Phys.-chem. Soc. 1903, No. 4, 81. 
Compt. rend. 137 (1903), 130. 
^) Liebig's Annalen 263 (1891), i. 
