Two combinatorial problems in the plane

The authors discuss two problems involvingn points in the plane and thet lines they form.     

The atomic absorption spectroscopy of chromium

Conditions were studied for the determination of trace amounts of chromium by atomic absorption spectroscopy. Solution matrix, flame composition, and extraction procedures were the variables studied. A detection limit of 0.006 p.p.m. of chromium was observed with an air-hydrogen flame and methyl isobutyl ketone as the solvent.     

Investigation of materials for making a carbon-support zinc-selective electrode

The usefulness of zinc orthophosphate and zinc mercuric thiocyanate to make a carbon-support electrode responsive to zinc was investigated. The best results were obtained with zinc orthophosphate, which produced a Nernstian response to zinc in the concentration range from 10(-5) to 10(-2)M. The electrode response was lowered by the formation of acidic oxides on the surface of the electrode. Different ways of minimizing this problem are discussed. Interference effects from copper(II) (K(pot)(Zn.Cu) = 1.0), cadmium (K(pot)(Zn.Cd) = 8.9) and lead (K(pot)(Zn.Pb) = 10) were observed.     

Voltammetry in dimethylsulphoxide-a review

A review is given of voltammetric studies using dimethylsulphoxide as supporting electrolyte, and includes details of inorganic and organic systems studied and of the reference electrodes developed for use in this medium.