116 Report of Schimmel § Co. J922. 



gram of benzene required 1340 calories. As the theoretical quantity of heat required 

 is calculated to be 208 calories 1 ) the thermal efficiency of the still was 15.5 per cent. 

 When other still-heads were employed, for instance copper gauze discs, or thin- 

 walled cylindrical glass beads 4 mm. long and 4 mm. in diameter, the thermal effici- 

 ency 2 ), with a 50 per cent, mixture of both hydrocarbons, was up to 47 per cent. 



L. Smith 3 ) publishes some laboratory notes on the efficiency of still-heads in 

 vacuum distillation. We agree with the author that the circumstances, in vacuum 

 distillation, are not fully comparable to those under atmospheric pressure; in the 

 present case, however, the method employed for testing was not sufficiently sensitive, 

 so that the values derived afforded no evidence towards the question which has been 

 elaborately studied by other authors 4 ). 



Years ago it has been demonstrated by A. Hantzsch 5 ) that it is possible to test 

 the constitution as well as the purity of terpenes by means of the ultraviolet ray 

 absorption. A. Miiller 6 ) employed this method for examining citronellol, geraniol, and 

 their derivatives. As the author communicates, it is sufficient, it is true, for obtaining 

 the pure alcohols and their acetates to make use of the ordinary distillation process, 

 whereas the purification of the cylic alcohols and their esters is said to be difficult. 

 Unfortunately though, he furnishes but insufficiently the constants of the preparations 

 under examination (the refractive index being nowhere recorded, and the optical rotation 

 only in part) from which the purity of the preparations might have been judged. The 

 solutions were prepared by means of optically pure alcohol. A citronellol obtained 

 from Java citronella oil (b. p. 112.5 at 8 mm., di 5 o 0.8612, a D20O 2° 16" 7 ) showed stronger 

 absorption than a citronellol obtained from citronellal by reduction (b. p. 113.2° at 8 mm., 

 diBo 0,8600, « D20O 4° 5'). A sample of geraniol (b. p. 108.2° at 9 mm., di 5 o 0,8836) purified 

 from its calcium chloride compound 8 ) showed a still lower absorption, and that of 

 reuniol lay between that of citronellol and geraniol, but nearer towards the latter. 

 With the acetates of the two alcohols the distance of the absorption curves was even 

 larger. With the cyclic alcohols (cyclisation was performed by treating the esters 

 with phosphoric acid at low temperature) the absorption bands approached each other 

 the closer, the more the esters were subjected to fractional distillation. The purest 

 preparations, ct/do-citronellol (b. p. 97 to 101° at 8Va mm., di 5 o 0.9023, a D20 o2°30' 7 ) 

 and cydo-geraniol (b. p. 96 to 98° at 11 mm., di 5 o 0.9462) showed but a feeble difference 

 in the position of the absorption bands; with the cyclic esters, however, the differences 

 were greater. The hydrogenated alcohols: — dihydrocitronellol (b. p. 113.5° at 15 mm., 

 d 15 o 0.8565) and tetrahydrogeraniol (b. p. 116 to 117.5° at 14.5 mm., d 1BO 0.8621), with 

 which the bands were located more towards the ultraviolet part of the spectrum, 

 possessed nearly the identical absorption. Since likewise the results of the chemical 

 examination indicated that in the hydrogenated alcohols the alkyl group occupied the 

 same position, the alcohols proved to be 2 : tf-dimethyl octanol-8. 



With regard to earlier chemical investigation 9 ), the author, basing on his optical 

 examination, arrives at the conclusion that reuniol is merely a mixture of citronellol 



x ) Journ. Soc. chem. Industry 38 (1919), 38 T; Bericht (German) 1920, 101. — 2 ) Phil. Mag. VI, 42 (1919), 

 633. — 3 ) Journ. f. prakt. Chem. II, 102 (1921), 295. — *) Cf. Bericht (German) 1920, 101. — 6 ) Cf. Report 

 April 1912, 156. — 6 ) Bert. Berichte 54 (1921), 1466. — ') The direction of the rotation is not stated. 

 — 8 ) In a paper published in the Deutsche Parfiimeriezeitung dealing with the identical subject the author 

 believes this calcium chloride compound to have been discovered in our laboratory. This is a mistake. This 

 compound was first obtained by O. Jacobsen (Liehig's Ann. 157 [1871], 234. — 9 ) Cf. Gildemeister and Hoffmann, 

 The Volatile Oils, 2 nd ed., vol. 1, p. 364. Report October 1904, 119. 



