Showing papers in "Analytical Chemistry in 1964"

Theory of Stationary Electrode Polarography. Single Scan and Cyclic Methods Applied to Reversible, Irreversible, and Kinetic Systems.

Abstract: was developed for solving the integral equations obtained from the boundary value problems, and extensive data were calculated which permit construction of stationary electrode polarograms from theory. Correlations of kinetic and experimental parameters made it possible to develop diagnostic criteria so that unknown systems can be characterized by studying the variation of peak current, half-peak potential, or ratio of anodic to cathodic peak currents as a function of rate of voltage scan.

Direct Titration of Epoxy Compounds and Aziridines.

Abstract: SIR: The determination of the oxirane ring in organic compounds has generally involved reaction with excess hydrochloric acid in a vayiety of solvents. Because the reaction LS slow, a t least a 15-minute reaction time is generally allowed before back titrating the excess acid. The determination of aziridines also requires back-titration techniques (1, 4) . Durbetaki (2) described a direct titration of epoxies with anhydrous hydrogen bromide in acetic acid. While this method is rapid and capable of good results, the reagent, which fumes profusely in air, requires special handling and freque it restandardizations for accurate analyses, The following method employs a stable, readily available, titrant which can be used for the direct titration of oxiranes and certain aziridines. The sample is dissolved in chloroform and titrated to a crystal violet end point with standard perchloric acid (in acetic acid or dioxane) in the presence of an excess of a soluble quaternary ammonium bromide or iodide. For epoxides eithereagent can be used, but the quaternary bromide is satisfactory for virtually all the materials usually encountered and is recommended over the iodide because of economy and better cd,orability. With aziridines, however, the iodide is preferred as it gives more rapid reactions and sharper end point3.

Infrared Spectra of Transition Metal Alkoxides.

Abstract: : The infrared spectra of a number of transition metal isopropoxides and tetra tertiary butoxides were obtained from 5000 cm-1 to 285 cm-1 for the first time. The spectra were compared to existing infrared data on these classes of compounds. Characteristic absorptions for the isopropoxy group have been found at 1160 to 1175 cm-1 and at 1120 to 1140 cm-1. They are assigned to isobranching vibrations. The isopropoxides exhibit a doublet at about 1375 cm-1 and 1365 cm-1 characteristic of the gem-dimethyl structure. The major feature of the spectra is a very strong band in 1000 cm-1 region assigned as the C-O stretch vibration, which is shifted by the influence of the specific metal atom on the C-O vibration. The butoxides have four characteristic absorptions at about 785 cm-1, 900 cm-1, 1010 cm-1, and 1190 cm-1. The band in the 1000 cm-1 region appears to be the C stretch vibration, the other bands are attributed to skeletal vibrations of the tert-butyl group. The typical C-H deformation of the tert-butyl group is observed at about 1360 cm-1 with a weaker band at 1380 cm-1. In the medium infrared region to 285 cm-1 a small number of very strong absorption bands are found for the tert-butoxides. The results suggest the region would be very satisfactory for characterizing tert-butyl compounds. (Author)

Simultaneous Determination of Mercury and Arsenic in Biological and Organic Materials by Activation Analysis.

Abstract: A method was developed to determine quantitatively nanogram amounts of mercury and arsenic in biological and organic base materials. After neutron irradiation of the sample in a nuclear reactor, followed by a chemical separation based mainly on distillation of volatile compounds of the elements, mercury and arsenic are determined by gamma spectrometry. The sensitivity limits are about 5 x 10/sup -4/ ppm for mercury and 10/sup -3/ to 10/sup -4/ ppm for arsenic when a sample weighing about 0.5 gram is irradiated for 2 to 3 days in a thermal neutron flux of about 10/sup 12/ n/cm/sup 2/second. The samples produced after the chemical separation are usually of high radiochemical purity. It is therefore possible to predict a sensitivity of about 10/sup -5/ ppm for mercury and 10/sup -4/ to 10/sup -5/ ppm for arsenic if the neutron irradiation is performed in a higher flux, say a few times 10/sup 13/n/cm/sup 2/-second, and if certain improvements in the radioactivity measurement technique are introduced. (auth)