The Limonene Group of Terpeyes. 
329 
The hydrogen chloride is not easily removed and traces of chloride 
are apt to remain. The regenerated hydrocarbon is a mixture of limo¬ 
nene and dipentene 19 . 
Preparation. 
When dry hydrogen chloride is passed into a dry solution of limonene 
or dipentene in carbon disulphide the monhydrochloride alone results. 
For technical details compare the original. 20 Dipentene monhydro¬ 
chloride can also be prepared by splitting off a molecule of hydrogen 
chloride from dipentene dihydrochloride 21 . 
Identification. 
The monhydrochlorides can easily be identified by means of the 
hydrochlornitrolaminebases. The preparation and purification of the 
hydrochlornitrolbenzylaminebase is easily carried out 22 . 
Dipentene-dihydrochloride. 
Synonyms. 
Muriate Citre — Th. de Saussure, 1820. 
Camphre de Citron — J. Dumas, 2 1833. 
Citrene chlorhydrate — J. Dumas, 2 1833. 
Festes salzsaures Citronenoel — Blanchet & Sell, 4 1833, 
Salzsaures Kautschin — Himly, 5 1835. 
Hydrochlorate de Citrene — Laurent, 6 1837. 
Camphre solide 7 de citron — Soubeiran and Capitain. 8 1840. 
Chlorwasserstoffsaures Carven — Schweizer, 9 1840. 
Chlorwasserstoff Terpin — List 10 1848. 
Bichlorhydrate d’essence de Terebenthine — Berthelot, 11 1852. 
Dichlorhydrate de terpilene — Berthelot, 12 1861. 
Zweifach chlorwasserstoffsaures Terpilen — Oppenheim, 14 1864. 
Dihydrochloride of citrene — Yoshida, 15 1885. 
Cynen dihydrochlorid—Hell& Ritter, 16 1884. 
Dipenten-Dihydrochlorhydrat — Wallach, 17 1884. 
Chlorhydrate de terpelene — Bouchardat & Lafont, 18 1886. 
Dipenten-Dihydrochlorid — Wallach 17 1887. 
History: 
Dipentene dihydrochloride is one of the oldest characteristic terpene 
derivatives. The so-called artificial camphor, the pinene monhydro¬ 
chloride alone has claim to priority. 19 In an article “ Sur la combinaison 
des acides avec les substances vegetales et animales.” Thenard in 1807 
mentions a crystalline substance which resulted upon the absorption of 
hydrogen chloride by lemon oil. There can scarcely be any doubt as to 
the identity of this substance. At least Blanchet and Sell 4 mention 
Thenard as the discoverer of the compound under consideration. The 
