NOTES ON SCIENTIFIC RESEARCH. 63 
In the experimental part of the paper we find the constants of some bodies that 
come into consideration for our special domain, viz., those of salicylaldehyde, anisalde- 
hyde, methyl and ethyl salicylates. 
When investigating a new range of alkyl and aryl derivatives of methylenecamphor 
for their optical behaviour, H. Rupe’) was able to confirm, as had previously been 
established, that certain laws rule the influence of some groups on the rotatory power. 
On comparing the rotatory dispersive power of the compounds of the methylenecamphor 
group, some hydrocarbons derived from citronellal?), and a number of menthol and 
myrtenol esters, he further found that [«]F — [@]c — const. for homologous compounds. 
This constant may be written as function of the wave-length, in a formula ascertained 
by Hagenbach?). In this way the “characteristic wave-length” is obtained for the 
corresponding range of compounds, and it has proved to be a useful auxiliary for 
estimating the dispersion curves. Availing himself of the characteristic wave-length, 
Rupe established the term of “relative anomalous rotatory dispersion”. Some of the 
compounds prepared by Rupe have such a dispersion. 
In the ninth publication by J. Kenyon and R. H. Pickard*) on the investigation 
on the dependence of rotatory power on chemical constitution, entitled, “The co- 
ordination of the rotatory powers of menthyl compounds, of the menthones and of 
the borneols”, the constants or the optical behaviour of numerous derivatives of 
these terpene bodies are described. Among others, the following were examined: 
d,l-menthyl oxalate, and numerous I-menthyl esters of substituted benzoic acids, 
I-menthyl hydrogen succinate, l-menthyl 2-methoxynaphthoate, I-menthyl phenylcarbamate, 
di-l-menthyl sulphite, and a great number of ureas and derivatives of carbamic acid. 
On account of observations of the rotatory powers, refractivities and molecular 
solution-volumes of borneol, cinchonicine and benzoyl cinchonicine in certain solvents, 
D. H. Peacock®) arrives at the conclusion that modifications of [@] according to con- 
centration are not caused by changes of the active molecules, but by alteration of 
the speed of light rays in the solvent. As regards the theoretical considerations 
which bring the author to this idea, we must refer to the original. 
Having continued former investigations, W. P. Jorissen and J. A. Vollgraff*) report 
on the electric conductivity of mixtures of oxygen and autoxidising vapours of benz- 
aldehyde and pinene. They this time used oxygen from the air and increased the 
surface of vaporization. The vaporization was accelerated by keeping the oxygen in 
motion along the surface of the liquid, a uviol lamp being employed for irradiation. 
The authors found that under the influence of irradiation the autoxidation- of both 
compounds increases the electric conductivity of oxygen. The electric conductivity 
of carbon dioxide is not increased by the presence of benzaldehyde or pinene. 
Re polymerization of styrene see p. 78. 
As to the products obtained from citronellal through exposure to the light, see p. 81. 
: 
1) Liebigs Annalen 409 (1915), 327. — 7%) Comp. Report April 1914, 130. — %) Zeitschr. f. phystk. Chem. 
89 (1915), 582. — *) Journ. chem. Soc. 107 (1915), 35. — 5) Ibidem 105 (1914), 2782. — *%) Chem. Weekblad 
12 (1915), 93; Chem. Zentralbl. 1915, I. 1049. See likewise Ibidem 1906, Il. 295. 
