摘要:

AbstractAccording to Raper's hypothesis, the quinone of 5:6‐dihydroxy‐2:3‐dihydroindole‐2‐carboxylic acid is the red coloured precursor of melanin, obtained by the oxidation of tyrosine with tyrosinase. This paper deals with some derivatives of this “red substance”, the structure of which is still unknown, with phenylhydrazine and substituted phenylhydrazines. No reaction products could be isolated, however, with hydroxylamine, or with semicarbazide. In connection with observations of Jacobs and of Breijer attention is drawn to the fact, that the “red substance” may be of importance as an anti‐pernicious principle and that premelanin of the skin‐epidermis possibly plays a r

ISSN:0165-0513    

DOI:10.1002/recl.19390581102

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

摘要:

AbstractIt is shown that inosose, a cyclose prepared fairly recently by Posternak by oxidation of meso‐inositol with concentrated nitric acid, can be obtained in a much higher yield by the biochemical oxidation of the said cyclic polyalcohol with the aid of the acetic acid bacteriumAcetobacter suboxydan

ISSN:0165-0513    

DOI:10.1002/recl.19390581103

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

摘要:

AbstractAn investigation of the influence of the halides of four alkali metals on the lowest temperature at which a reaction between methane and oxygen can be observed.

ISSN:0165-0513    

DOI:10.1002/recl.19390581104

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

摘要:

AbstractBeschreibung einer Apparatur, mit welcher in 10 Minuten die Mikro‐Analyse von Edelgas‐Stickstoffmischungen durchgeführt werden kann.Beschreibung einer Apparatur, mit der die Mikrogasanalyse von Edelgas‐Stickstoffmischungen in 10 Minuten durchführbar ist. Die Absorption des Stickstoffs wird mit Hilfe flüssigen Lithiums durchgeführt. Genauigkeit ± 0.2% N2. Minimalgasmenge etwa 1

ISSN:0165-0513    

DOI:10.1002/recl.19390581105

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

摘要:

AbstractTitanium and zirconium, both in their hexagonal and in their regular forms, form a continuous series of solid solutions with a transition point minimum for the atomic ratio 1:1. In this composition, transition from the hexagonal close‐packed to the body‐centred cubic modification takes place at 545° C, i. e. at a temperature more than 300° C below the transition temperatures of the pure components (fig. 6). The transition point of pure titanium was newly determined and found to be 885° ± 10° C. In the melting point diagram there is again a minimum which is probably located at the atomic ratio Ti: Zr = 2 : 1 and at a temperature of about

ISSN:0165-0513    

DOI:10.1002/recl.19390581106

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

摘要:

AbstractWhen sheets of iron are brought into contact with aqueous solutions of definite pH‐values, a diffusion of hydrogen through the iron takes place in all cases where the liquid dissolves iron under development of hydrogen. No diffusion takes place if the pH‐value of the liquid is such, that there is no evolution of nascent hydrogen. This proves that atoms of hydrogen formed by the chemical reaction may enter the iron but that the hydrogen ions contained in the solutions are unable to do so.In accordance with these results it was found that hydrogen atoms formed in hydrogen gas by means of an incandescent tungsten coil may enter readily into iron plates at room temperature. A vessel, having a wall of iron and filled with hydrogen can be evacuated in this way. As hydrogen can only diffuse through the iron from the side where atoms are produced, it accumulates on the other side of the iron wall and diffusion takes place against an atmosphere of hydrogen of any press

ISSN:0165-0513    

DOI:10.1002/recl.19390581107

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

摘要:

AbstractThe bromination of 2,6‐dibromopyridine in the gaseous phase and in the presence of pumice as a contact substance has been reinvestigated in the temperature range of 500‐580°; besides 2,4,6‐tribromopyridine, which is the main product of the reaction as already found by den Hertog and Wibaut1), a tetrabromopyridine of melting point 105‐106° is formed; this compound is 2,3,4,6‐tetrabromopyridine. A very small quantity of pentabromopyridine is

ISSN:0165-0513    

DOI:10.1002/recl.19390581108

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19390581109

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19390581110

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19390581111

出版商:WILEY‐VCH Verlag    

年代:1939

数据来源: WILEY