NOTES ON SCIENTIFIC RESEARCH. 83 
in all 5,5 p.c. of isoprene. The fraction boiling at 155 to 156° (pinene fraction) yielded 
8 p.c.; that boiling at from 169 to-175°, 0,5 p.c. and the fraction boiling above 175°, 
0 p.c. of isoprene. As may be seen, the last fractions, which, according to their b. p., 
might contain dipentene, furnished little or no isoprene. Herty and Graham further 
heated in the isoprene lamp the turpentine oil from Pinus serotina*). In accordance 
with its high content of limonene, it yielded 12 p.c. of isoprene. Pine oil, which chiefly 
consists of terpineol, yielded 4 p.c. of isoprene. 
Finally an oil was investigated, which is obtained as a by-product in blowing off 
the digestors in the manufacture of wood pulp from spruce fir. It boiled in the main 
between 171,3 and 174,9° (dis. 0,8639; np 1,4916) and consisted chiefly of cymene. 
Isoprene was not obtained from this product. 
Camphene. Through the action of dilute aqueous hypochlorous acid on camphene, 
G. G. Henderson, I. M. Heilbron and M. Howie?) obtained a chlorohydrin Cio Hig Cl- OH, 
melting at 93°. It reacts with aqueous and alcoholic solutions of potassium hydroxide 
forming isocamphenylanaldehyde, and furnishes camphene dichloride with phosphorus 
pentachloride. When treating the chlorohydrin with zinc and alcohol, isoborneol is 
formed, which shows that the chlorohydrin is identical with chlorozsoborneol. When 
oxidized with chromic acid, it is converted into a crystalline chloroketone, CyoHi; OCI 
(m. p. 132°), which on heating with zinc and alcohol yields camphor. 
Regarding the constitution of fenchene, see page 95. 
Iimonene. On page 137 of our Report of October 1911, we discussed a paper 
by G. Vavon on the reduction of limonene. Detailed communications about this 
investigation have meanwhile been published by the author elsewhere*). The d-carvo- 
menthene (dihydro-limonene) obtained synthetically through the action of water on the 
magnesium derivative of limonene monohydrochloride has a lower rotation (a578 + 59 
and +89°; o4.,+117 and + 175°) than the product (457g + 97,39; G46 + 193°}4), 
resulting from the reduction of d-limonene. Vavon does not say anything as to the 
other properties of the synthetic product. Carvomenthene, obtained by reducing 
limonene, forms with hydrogen chloride a hydrochloride, CioHiyCl, boiling at 85 to 86° 
(13 mm.), 180 to 185° (ordinary pressure, partial decomposition); das 0,934; npo10 1,460. 
In connection with this investigation, Vavon®) reports on the speed of the reaction 
in catalytical hydrogenations with platinum and on the exhaustion of the catalyst. If a 
sufficient quantity is used for reducing the limonene, the speed of the reaction remains 
almost constant during the whole process. If less platinum is taken, the reaction 
proceeds more slowly, and if still smaller quantities are used, the reaction remains 
incomplete, i.e. only the extracyclic double linking is reduced. Heating to a very high 
temperature reduces the activity of platinum, so that only easy reductions can be 
executed with its aid, such as those of the extracyclic double linking of limonene. 
As will be remembered, A. Blumann and O. Zeitschel®) isolated from resinified 
turpentine oil the alcohol verbenol and the ketone verbenone. Both bodies must have 
formed through autooxidation of pinene, which oxidation takes place in an abnormal 
1) Comp. Report November 1908, 120. — 7) Journ. chem. Soc. 105 (1914), 1367. — 3) Bull. Soc. chim. 
IV. 15 (1914), 282, — +4) The rotation refers to rays 7 = 578 and ) = 436 of the mercury lamp. — 5) Bull. 
Soc. chim. 1V. 16 (1914), 287. — %) Berl. Berichte 46 (1913), 1178; Report October 1918, 103. 
6* 
