Crystal chemistry of AB2X4 (X = S,Se, Te) compounds

An attempt is made to correlate the crystal structures of ternary chalcogenides of composition AB₂X₄ with the cationic radius ratio and a pseudo force-constant involving their electronegativities. The resultant diagram adequately resolves structures based on the types K₂SO₄, monoclinic, olivine, MnY₂S₄, Th₃P₄, and CaFe₂O₄ but structure types based on spinel, Cr₃Se₄, and Ag₂HgI₄ are not resolved. Crystal chemical arguments are used to explain these observations and to advance reasons for the successes and failures of this method for predicting structure types.     

Derivatives of unsaturated phosphonic acids

Russian Chemical Bulletin -     

Microwave chemical processing

The chemical industry admits to minimal use of microwave power because of its high capital and operating costs relative to steam, combustion, electrical, and other traditional sources of energy. Other valid historical and persistent reasons for their lack of proper use include: a poor conceptual understanding of microwaves by chemical professionals, their unwillingness to replace existing adequate methods with radically new technology, the infancy of the microwave industrial power supply, and unfamiliarity of microwave power systems manufacturers with the chemical industry. In years past, the North American chemical industry had few competitors and profits were generally large. Environmental regulations were few and product quality was less a concern than production volume. The microwave power industry relied on the government and communications for lucrative sales. Those days appear over. Chemical manufacturers must probe every technology to achieve the edge necessary to stay competitive while meeting environmental stewardship demands. Microwave power has always offered unique advantages in heating materials selectively and/or quickly to high or preselected temperatures with fast control response. In the cases discussed in this paper, novel applications of microwave power afford: faster production, a reduction in product contaminants, reduced downtime, reduced waste, product quality improvements, and better pollution control.     

Catalytic determination of selenium with a picrate-selective electrode

A method is described for the determination of selenium, based on its catalytic effect on the picrate—sulfide reaction. The determination involves a variable-time kinetic procedure using potentiometric monitoring with a picrate-selective electrode and automatic measurement of the time required for the potential to change by a preselected amount (5.0 mV). Selenium in the range 3–30 μg was determined with an average error of about 4% and relative standard deviations of about 2%. The reaction can also be followed spectrophotometrically.     

Liquid-phase oxidation of bromovinyl compounds with molecular oxygen

Liquid-phase oxidation of bromovinyl compounds with the aim to obtain the corresponding α-bromo acids was studied. Original Russian Text R.B. Bayatyan, B.E. Bayatyan, L.A. Saakyan, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 11, pp. 1870–1873.