The numbers of chiral and achiral alkanes and monosubstituted alkanes

Whereas the theory for the enumeration of the optical isomers of the lakyl radicals and the alkanes has long been understood, this is not the case for the corresponding archiral isomers. We present for the first time recurrence formulae for counting the number of archiral isomers of the alkyl radicals and the alkanes. For chiral and archiral alkanes and monosubstituted alkanes, numerical results up to C₁₄ are tabulated.After presenting the history of the problem and the necessary definitions, we proceed to derive functional equations on the various generating functions, which readily yield the more explicit recurrence formulae usefule for numerical calculations. In the process, we first re-derive Pólya's expression for planted steric trees using his classical enumeration theorem. This result is then extended to the enumeration of free steric trees using the now standard tree-counting method due to Otter and known as a dissimilarity characteristic equation.By definition, a steric tree is a quartic tree (all points having degree 1 or 4) in which the four neighbors of every carbon point are given a tetrahedral configuration. Building on the methods of the first two authors for counting chiral and archiral trees in the plane, we obtain the formula for counting achiral steric trees, thus setting a problem first enunciated by van't Hoff and Le Bel in 1874.     

Thermal behaviour of chromium (III) perchlorate hexahydrate

Thermal behaviour of intimate mixtures of chromium(III) oxide and lithium¹, potassium², rubidium³, cesium³ and thallium(I)⁴ perchlorates revealed that chromium(III) oxide not only catalyses the decomposition by lowering the decomposition temperatures of the pure metal perchlorates but also chemically interacts resulting in the formation of metal dichromate. The oxidation of chromium(III) into the hexavalent state is attributed to the abstraction of oxygen from the perchlorate moiety during the decomposition. In this context, it was thought interesting to study the thermal behaviour of chromium(III) perchlorate and to identify the decomposition products in order to find out whether chromium(III) is oxidized into chromium(VI) by the perchlorate group. Except for a report⁵ on the preparation of chromium(III) perchlorate with different molecules of water of hydration no work seems to have been carried out on the thermal decomposition of this compound. In the present study, the decomposition characteristics are followed by TG and DTA techniques and the decomposition products have been examined by chemical analysis, X-ray powder diffraction patterns and infrared spectral measurements.     

Alkaloids ofPetilium raddeana II. Structures of petisine and petisinine

The alkaloids imperialine, imperialone, peumisine, petiline, petilidine, and the new bases petisine (I) and petisinine (III) have been isolated from bulbs ofPetilium raddeana (Regl.) Vved. On the basis of spectral characteristics and passages to a known compound, the structure of 3β-hydroxy-Δ²²(N)-22,26-iminocholestane-6,23-dione has been established for (I) and petisine 3β-glucopyranoside for (III).     

The dipole moment of HNO in its ÃA″ excited state determined using optical—optical double resonance stark spectroscopy

The Stark splittings and rotational asymmetry splittings of a number of levels of the ùA″ excited state of HNO have been measured using the sub-Doppler technique of optical—optical double resonance, μ_a is found to be 1.08 ± 0.01 D for the 100 vibronic state, and 1.05 ± 0.01 D for the 020 vibronic state. These values are to be compared with a recently determined ground state value of μ_a = 0.996 D. The asymmetry splittings of some of the levels studied are considerably larger than predicted from the known rotational constants, indicating minor rotational perturbations.     

Transient analysis of a vibrating reed: Error analysis

The error analysis for the transient vibrating reed test is developed based on a linearized approximation. Tables are given for the efficient utilization of the equations in evaluating the accuracy range of test data.     

An automatic absorptiometric method for the determination of nitrate

A method has been developed for the determination of nitrate with the Technicon Autoanalyser in the range 2–10 p.p.m. The method depends on the reduction of nitrate to nitrite by hydrazine in alkaline solution, with copper as a catalyst. The nitrite produced diazotises sulphanilamide and the product is coupled with N-(1-naphthyl) ethylenediamine, to give a red dye, the absorbance of which is measured at 550 mμ. A relative standard deviation of 3–4% is obtained.     

The extraction of elements with cyclic solvents and its application to geochemical analysis

The extraction of the elements Zn, Cd, Hg, Ga, In, Tl, Sn, Pb, As, Sb and Bi into the solvents cyclohexanone, cyclohexanol, and cyclohexane from hydrochloric acid solutions, has been studied. Cyclohexanone is a more efficient but less selective extracting agent than cyclohexanol while cyclohexane has little extracting power. Solvent extraction of hydrochloric acid solutions of materials of geochemical interest into cyclohexanone has been used to enrich trace elements prior to spectrochemical analysis.     

Metallfällungen mit Nitropnenylarsinsäuren

Zusammenfassung Die qualitative Fällung von Metallionen mit den drei isomeren o-, m- und p-Nitrophenylarsinsäuren wird beschrieben und auf Unterschiede der p_h-Werte des Fällungsbeginnes hingewiesen. Die Beeinflussung des Fällungsbeginnes durch die Stellung der Nitrogruppe wird hervorgehoben.

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Summary The precipitation of metal ions by means ofo-, m-, andp-nitrophenyl arsonic acids is described. The differences of the p_H values of the start of the precipitation are pointed out. The effect of the position of the nitro group on the beginning of the precipitation is stressed.

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Résumé On décrit la précipitation qualitative d'ions métalliques par les trois isomèreso., m. etp. de l'acide nitrophénylarsonique et l'on donne des indications concernant les différences de valeur du p_h lors du commencement de précipitation. On met en évidence l'influence de la position du groupe nitro sur le commencement de précipitation.

     

Application of multiparameter equations to calculation of the mutual solubility in water-organic solvent binary systems

The solubility of organic liquids in water and of water in organic liquids is primarily determined by the capability of organic liquids for hydrogen bonding. Adequate generalization of the solubility data is possible only with multiparameter equations taking also into account other properties of organic components, including the cohesion and molar volume.