Comparative substoichiometric extraction of silver with potassium salts of ethyl, propyl, butyl, pentyl and benzyl xanthates

A rapid and sensitive substoichiometric radiochemical method has been developed for the comparative extraction and quantification of silver with potassium salts of ethyl, propyl, butyl, pentyl and benzyl xanthates from hydrochloric, nitric and sulfuric acid media into chloroform. The effect of 0.1–4M H⁺ ion concentration of the respective acid on the substoichiometric extraction of silver was critically studied. The efficiency of the method developed was tested by the determination of 10–100 g silver in standard solutions with an average percentage of error better than 2. The methods developed have been utilized to determine silver content in photofilm washing collected from various photostudios in Tirupati, India.     

Crystal structure of N-m-tolyl phthalimide

N-m-tolyl phthalimide, C₁₅NO₂H₁₁ crystallizes in the space group Cc with unit cell dimensions,a=8·54(1),b=19·89(2),c = 7·59(1)A, β=114·53(1)° andZ=4.V=1173(2)A³,D _m =1·35(1),D _c = 1·344 mg.m⁻³,M _r =237 λCoK_a=1·7903A. The structure was solved byMULTAN and refined to an R-factor of 0·116 for 632 counter reflections. The molecules are held together by van der Waal’s forces. The angle between the tolyl plane and the plane through the phthalimide group is 53·4(4)°. Contribution No. 607.     

New synthesis of flavanones catalyzed by l-proline

l-Proline is utilized as an efficient organocatalyst for the synthesis of substituted flavanones and chalcones in good yields. The efficiency of the catalyst was proved with a variety of substrates ranging from electron-deficient to electron-rich aryl aldehydes and 2-hydroxyacetophenones.     

NDDO MO calculations

Three valence-only schemes based on the Roby version of NDDO MO theory, which differ only in the core-valence treatment and the choice of the basis set, have been applied to the study of molecules containing first-row atoms. Orbital energies, charge distribution, dipole moments, field gradients, and a few other one-electron molecular properties are calculated to satisfactory accuracy. The schemes appear unreliable in the prediction of barriers to internal rotation in molecules, presumably due to errors in the core contribution to the total energy. An alternative treatment is suggested.     

A study of blanketing sporadic E in the Indian equatorial region

The paper describes the nature of the sporadic E layer of blanketing type observed at Kodaikanal (Lat. 10°·2 N; Long. 77°·5 E; dip: 3°·5 N). It is shown that in the Indian equatorial region, the frequency of occurrence of this type of E _s is abnormally large when compared to similar latitudes in the west and that changes of large magnitudes occur in the F2 layer of the ionosphere as well as in the horizontal force of the earth’s magnetic field simultaneously with the appearance of the blanketing E _s . Lunar effects have also been shown to exist both in the time of appearance of blanketing E _s and in its strength. Some evidence exists to show that blanketing E _s as well as the blanketing frequency,f _b E _s , have a biennial maximum. These characteristics are discussed as part of the Far East Anomaly.     

The superconducting penetration depth from the semiclassical model

The semiclassical approach of Onsager and Pippard has been very successful in relating the electronic properties of a normal metal to its band structure and fermi surface. This paper extends the method to a superconductor. A generalized London equation relating the supercurrent density to the vector potential is obtained, in terms of band and fermi surface parameters and an energy gap which may be anisotropic. The results allow an interpretation of measured penetration depths directly in terms of the electronic and gap structures of the superconductor. They lead to easy physical visualization of the origin of anisotropies and other features of measured penetration depths.     

Alternative mechanisms for cyanide anion exchange with acetonitrile

Mechanisms for the recently observed exchange of cyanide anion in acetonitrile have been investigated by means of semi-empirical MNDO molecular orbital calculations. A prototropic type mechanism $\text{via}$ a cyclopropane intermediate is the most likely candidate. The previously proposed concerted migration is indicated to be the least favourable reaction pathway.