As is well known,' a natural, all-trans carotenoid is partially converted by heat or iodine into a mixture of its cis-trans isomers. Simultaneously a decrease in the intensities and wave lengths of the extinction maxima takes place in the visible spectral region. These observations are in accordance with the theoretical conclusionzJ that among all stereoisomers of a polyene the all-trans form, possessing the extended coplanar structure, must have the greatest color intensity.It was recently shown,' however, that the bending of the molecule does not necessarily involve a decrease in the extinction in every spectral region. On the contrary, such a spatial change, brought about, e. g., by iodine catalysis, causes the appearance of a new marked maximum which we call the "cis-peak." The latter is located somewhere within the region 320 to 380 m p , e. g., a t 339.5 mp for p-carotene in hexane. The distance between this peak and the longest ,vave length maximum is approximately constant, 142 mp for all CU-carotenoids tested so far.It seemed probable that the different stereoisomers present in the complicated equilibrium mixture would contribute unequally to the total effect observed, the contribution of the sterically symmetrical all-trans form being practically zero. This assumption was first verified for the p-carotene stereoisomeric set,' and in the present paper we report more extensive pertinent rcsults for the y-carotene set and espeaally for the lycopene set.In the investigation of @-carotene it was found6 that neo-p-carotene U, which is adsorbed above natural 8-carotene in the Tswett column, shows a considerably smaller cis-peak than the equimolecular solution of the stereoisomeric mixture obtained with iodine. In contrast, the isomers adsorbed below natural 8-carotene possess a much higher cis-peak than the mixture.In order to obtain a broader experimental basis (1) For literature see our recent paper. A. PolgAr and L. Zrch-(2) L. Pading, Forlschr. Chrm. orgorr. Noburstof#, 8, 203 (1939). (3) R. S. Mullikcn, J . Chrm. Phys., I , 364 (1939); RII. Modorrr (4) L. Zechmebtcr and A. PolgcU, Tma Jownnu,, 66, 1522 (1948). ( 5 ) Pdcrllon 4. Fig. 4. rseister. Tu19 JOURNAL. 64, 1850 (1942). Ply*.. 14,205 (1942).for theoretical work, it is necessary to investigate whether a stepwise trans --* cis change of an alltrans conjugated system will raise continuously the cis-peak, or whether the peak will reach a maximum intensity and then decrease again as the number of cis double bonds in the molecule increases. Particularly suitable materials for such an investigation are offered by nature in the form of pro-y-carotene, CUHW, and prolycopene, CloH'6, which have been isolated from several fruits6but not yet obtained artificially.The positions of the maxima of these isomers dissolved in petroleum ether differ from those of the respective all-trans forms by 31 and 35 mp, respectively. Since the difference between nlltrans carotenoid hydrocarbons and their spectroscopically closest stereoisomers is about 4 to G mp (corresponding ...

Spores of the fungi Rhizopus suinus, Mucor dispersus andAspergillus melleus were tested with respect to their resistance to ultraviolet of wave-length 2650 A. Sigmoid survival curves were obtained for the fungi Rhizopus suinus and the minus strain of Mucor dispersus when spores from 4-day cultures were irradiated. Survival curves describing a logarithmic order of death were exhibited by spores from 4-day cultures of Aspergillus melkeus.The three species of fungi showed marked differences in susceptibility to radiation (2650 A). A combination of the differences in pigmentation, size of the spores and the number of nuclei may account for the differences in susceptibility observed.A trend of increasing resistance to radiation with increased age was observed for spores of Rhizopus suinus.

A study of the solvent effects in the spectra of non-ionic compounds to whose structure a zwitter ion form makes appreciable contribution (particularly in the excited state) has revealed three distinct effects: 1. A shift of absorption bands to greater wavelength with increasing refractive index, as predicted by Kundt's rule. This is ascribed to the effect of electronic polarizability on the zwitter ion structure, and is seen unmixed with the other effects only when the solvents are hydrocarbons or aryl halides. 2. A further shift which appears with most solvents other than hydrocarbons and aryl halides, and is ascribed to orientation of molecules of nonuniform polarizability. 3. The Kuhn-Brockmann effect—a large shift which appears whenever hydrogen bonds between the solvent and solute occur. This is believed to be due to the stabilization of the zwitter ion by the electrostatic nature of the hydrogen bond. No correlations of the spectra of phenolphthalein, p-rosaniline hydrochloride, or iodine with the properties of the solvent were found.

A Method for Standardization of Chromatographic Analysis 1905 temperature when obtained pure. It decomposes at 52°as compared with the crude product which explodes if heated rapidly to 50°. The pure azide does not readily detonate when attacked with a hammer.

A number of streak reagents, used in detecting zones of colorless substances on the chromatographic column, have been studied in regard to their usefulness in the detection of certain compounds. These reagents are all sensitive at concentrations of 0.01 molar.Several new streak reagents have been developed.