Notes on scientific research. 117 



and geraniol (with at least 60 per cent, of geraniol), and that it must be struck off from 

 chemical literature. 



The absorption power of ultraviolet rays by various phenols and phenol ethers 

 has been studied by Th. H. Durrans 1 ). Jsoeugenol proved to absorb ultraviolet rays 

 much more than eugenol, and by methylating a phenol hydroxyl,. e. g., in isoeugenol, 

 the absorption power for ultraviolet light is doubled. The absorption is likewise 

 raised, in a still higher degree, by introducing the allyl side-chain, whereas by the 

 propenyl side-chain the power of absorbing ultraviolet light becomes very small, as 

 was shown by comparison of anisole, anethole, and methyl chavicol. 



The investigation started by Rupe on the influence of the constitution on the 

 optical rotation of active substances has been continued by A. Krethlow and K. Lang- 

 bein 2 ). In order to obtain further insight into the relation between rotatory dispersion 

 and spectral absorption the authors examined such optically active substances as 

 show marked or at least incipient, selective absorption of light in the neighbourhood 

 of the visible spectrum as to their abnormal rotatory dispersion. Of 19 optically active 

 bodies examined, six were perfectly normal in their optical behaviour, as they showed 

 neither abnormal rotatory dispersion nor any selective absorption of light (amongst 

 then camphorylidene-3-acetic acid methyl ester and camphoryl-3-acetic acid). Seven 

 substances manifested anomalies in rotatory dispersion, amongst which were various 

 menthyl esters, e. g., of diacetoacetic and of pyruvic acids. Benzalcamphorylidene 

 acetone and styrylbenzoylacetic acid menthyl ester behaved polarimetrically normal, 

 but showed beginning spectral absorption. 



The authors deduct from their investigations that a parallelism between abnormal 

 rotatory dispersion and selective spectral absorption does not appear to exist. Amongst 

 33 bodies, only three (the white diphenylmethylacetoacetic and phenylbenzoylacetic 

 acid menthyl esters, besides the pale yellow diphenylmethylal camphor) were found 

 which showed both anomality in the rotatory dispersion and selective absorption of light 3 ). 



F. Eisenlohr 4 ) reports on the molecular refraction of higher-melting bodies, and how 

 the corresponding refractive indices are recalculated on the standard temperature of 20°. 



A. Muller 5 ) observed anisotropism in the melting point of dianisalc^cZohexanone 

 (prepared from pure c^/cZohexanone and anisic aldehyde). At 160 to 161°, the body 

 liquefied into an opaque mass which clarified suddenly at 1/1 °. The phenomenon of 

 voluntary spreading-out on water in a very thin film (long known with oleic acid and 

 other bodies) has been observed by A. Marcelin 6 ) with a series of other substances. 

 The experiments were carried out in the following manner: — When a small piece of 

 camphor is floated on water, the surface of which was sprinkled with talc powder, 

 one could observe how the talc grains were driven away from the camphor piece so 

 that an empty circle was formed round the latter. The diamete'r of this "halo" reached 

 a maximum depending upon the equilibrium ruling between the velocity of the dissolving 

 of the thin camphor layer formed, and of the re-formation from the camphor piece. 

 A series of photographs of this process was taken. From the area of the circle and 

 the loss in weight of the camphor piece the thickness of the layer was calculated. 

 Solid benzene (below 3° C.) showed the same phenomenon when floating on water. 



*) Rerfum. Record 12 (1921), 370. — 2 ) Liebig's Ann. 423 (1921), 324. — 3 ) Cf. Report 1918, 96. 

 4 ) Btrl. Her. 54 (1921), 2857. — 8 ) Ibidem 1481. — 6 ) Compt. rend. 173 (1921), 79. 



