330 Wisconsin Academy of Sciences , Arts and Letters. 
fact that Thenard recognized that the hydrochloric acid was added 
without causing a decomposition of the molecule adds to the interest of 
the discovery. 
In 1820 Saussure 1 prepared dipentene dihydrochloride in pure form 
and described the same. He calls attention to the physical differences 
between this “ muriate citre ” and the “ muriate terebinthine.” From it 
he also regenerated the hydrocorbon. 
J. Dumas, 2 in 1833, accepts the formula C 5 H 4 -f- y 2 H 3^ Ch for the 
“ camphre de citron.” 
In the same year Blanchet and Sell 4 characterize the “salzsaure 
Citronenol” as follows: “From ether it crystallizes in laminae with a 
silver lustre and of tuberose-like odor. It melts at 43° and sublimates 
at 50° without decomposition,” etc. Percentage of chlorine 33.5 p. c.; 
formula C 5 H 8 + Cl H. Thenard has tried to ascertain the composition 
of the compound by noting the quantity of hydrogen chloride absorbed 
by the oil. Saussure destroyed the substance with nitric acid and pre¬ 
cipitated the chlorine as silver chloride. He obtained 27.6 p. c. chlorine. 
Blanchet and Sell employed the lime method. These chemists also sup¬ 
posed that by the action of hydrogen chloride upon lemon oil two solid 
compounds are formed, the one of which decomposes into hydrochloric 
acid and oil when recrystallized from warm alcohol, the other being 
more stable. The latter is termed “ salzsaures citronyl ” (the substance 
under consideration), the other “ salzsaures Citryl.” 
Himley 21 (1835) obtained “ Salzsaures Kautschin” by passing hydrogen 
chloride into “Kautschin ” (dipentene) and regenerated the hydrocarbon 
by distillation with lime and rectification over potassium. 
Soubeiran and Captain 8 (1840) mention the readiness with which 
dipentene dihydrochloride decomposes: “II sufELt meme d'evaporer une 
dissolution alcoolique de ce camphre pour qu’il soit detruit en partie,” 
etc. They do not accept Blanchet and Sell’s view regarding the mixture 
of two isomers. They recognize the fact that the “ camphre de citron ” 
and also the regenerated “ citrene ” are optically inactive. 
Schweizer 9 (1840) assigns to his “ chlorwasserstoffsaures Carven,” the 
formula C 10 H 16 + Cl s H 2 . He regards it as isomeric with the solid 
compound obtained by the action of hydrogen chloride upon lemon oil, 
copaiva oil, and orange oil, with which it corresponds more or less in 
some of its properties. 
List 10 (1848) regards the chlorhydrate “Co 0 H too Cl 3 ” obtained from the 
terpin as isomeric with the one obtained by Blanchet and Sell and by 
Dumas. He claims cyrstallographic differences, also differences in 
melting points and solubility. 
Deville’s observation of 1849 is of some interest : “Les hydrates de 
terebenthine donnent avec l’acide chlorhydrique de 1’eau et du cam¬ 
phre de citron dont on peut retirer une huile qui par ut identique 
