Development and publication of new gravimetric methods of analysis.

A review is made of the factors affecting the accuracy of gravimetric methods, and which need to be investigated in the development of new methods. Recommendations are made for writing up such investigations for publication.

Determination of trace contaminants in hydrogenation catalysts by neutron-activation analysis.

A neutron-activation method has been developed for the determination of the active constituents and contaminants in hydrogenation catalysts. The active constituents of palladium and nickel catalysts (Pd and Ni) and Zn and Co contaminants present in small amount were determined by a direct instrumental method. A NaI(Tl) scintillator and a Ge(Li) semiconductor connected to a multichannel analyser were used for the measurements. A computer was used to evaluate the gamma-spectra. Contaminants present in small amount were also determined by means of a radiochemical separation method based on heterogeneous isotopic exchange on mercury(II) sulphide and zinc sulphide precipitates.

Application of displacement reactions in flame photometry-I: the determination of phosphate by a flame emission method.

Phosphate ions decrease the flame emission of calcium, but this effect can be partly offset by adding a second metal which partly displaces calcium from the non-excitable species. For the determination of phosphate the sample solution is divided into four equal parts; to each of these, various amounts of calcium and barium ions are added such that the total (molar) concentration of the metals is constant. Plotting the intensity measured at 630 nm vs. the calcium content of the solution gives a straight line, the slope of which depends on the concentration of phosphate ions present. The method is suitable for rapid determination of phosphate. Accuracy and precision are within the usual limits characteristic of flame photometric methods.

Studies on the melts of alkali metal acetates.

The density, viscosity, and electrical conductivity of alkali metal acetates were measured over the temperature interval between melting and decomposition. The apparent activation energies of the equivalent conductivities and viscosities were calculated. It has been concluded from the results that alkali metal acetates, similarly to alkali metal benzenesulphonates studied earlier, exhibit properties quite unlike those of alkali metal halides. In the dependence of equivalent conductivity on the nature of the cation, the anomalous behaviour of lithium salts appears to be due to association prevailing in the melt phase.

Spectrochemical analysis of hard metals by a rotating disc technique: effect of impregnation and complexing agents.

A spectrographic method has been developed for the simultaneous determination of the constituents W, Co, Ti, Ta and Nb and contaminants Fe, Ni, Or, Mn, Mg and Ca in hard metals. The samples were dissolved in hydrofluoric acid and nitric acid and the solutions stabilized with citric acid. Graphite discs were waterproofed in order to ensure control of the introduction of solution into the source. For the five types of hard metal samples studied no inter-element effect was observed. Titanium has also been determined by means of a double-beam optical spectrometer.

Investigation of alkali metal and ammonium tetraphenylborates by infrared spectrophotometry.

The infrared spectra of alkali metal and ammonium tetraphenylborates have been studied and an infrared spectrophotometric method developed for the determination of ammonium ions in the form of the tetraphenylborate. The N-H deformation vibration band appearing at 1405 cm(-1) in the spectrum of ammonium tetraphenylborate has been utilized for quantitative evaluation; the tetraphenyl-borates of the alkali metals do not exhibit absorption at this frequency. Thus ammonium ions can be determined as the tetraphenylborate in the presence of alkali metal ions without preliminary separation.

Application of direct thermometric analysis in iodometry.

Elementary chlorine was determined by a thermometric method using potassium iodide as reagent. The temperature rise corresponding to the heat of reaction was proportional to the chlorine content. Iodine formed in the reaction was also determined with sodium thiosulphate. The heat of the chlorine-iodide reaction is about five times that of the iodine-thiosulphate reaction. Direct determination with potassium iodide is simpler and more rapid than the indirect one.

Determination of nickel and copper by precipitation from homogeneous solution as their salicylaldimine complexes.

A method has been developed for the gravimetric determination of copper and nickel as their salicylaldimine complexes, by precipitation from homogeneous solution. The complexes are crystalline precipitates which are very easy to filter off and wash. The accuracy of the determinations is higher than that of the conventional precipitation method.

Application of chemiluminescent indicators in EDTA titrations.

The chemiluminescent indicators lucigenine and luminol are readily applicable to end-point detection in the EDTA titration of cadmium, zinc and nickel ions. Back-titration with copper(II) gives reproducible results. The end-point is indicated by the disappearance of the green chemiluminescence of lucigenine, or by the appearance of the bluish luminescence of luminol.

Determination of microgram amounts of metals by chronometric analysis.

The reaction between peroxidisulphate and iodide, modified by the addition of thiosulphate to show the Landolt effect, has been used for the determination of copper and iron in the range 1-100 mug ml , based on the catalytic effect of these ions. The procedure is rapid and simple, and the errors are less than 10%. The interference from iron in the determination of copper may be overcome by the addition of a masking reagent such as fluoride.

Precipitation of manganese ammonium phosphate from homogeneous solution.

Precipitation of manganese, zinc and cadmium ammonium phosphates from homogeneous solution by decomposition of metal EDTA complexes by boiling with hydrogen peroxide in presence of phosphate has been investigated. Precipitation of Cd is not quantitative, but of Mn is complete in 2 hr, and of Zn in 6 hr.

Radiometric acid-base titrations.

Acid-base titrations can be performed with radiometric end-point detection by use of labelled metal salts (e.g., ZnCl(2), HgCl(2)). Owing to the formation or dissolution of the corresponding hydroxide after the equivalence point, the activity of the titrated solution linearly increases or decreases as excess of standard solution is added. The end-point of the titration is determined graphically.

Thermoanalytical properties of analytical grade reagents V. Sodium halates.

The thermoanalytical properties of sodium halates have been investigated by means of a derivatograph and a visual DTA instrument. The thermal decomposition of the compounds studied was found to proceed only in the melt phase to a measurable extent, while the corresponding sodium halides were being formed. For sodium chlorate the formation and decomposition of sodium perchlorate could also be observed. The comparison of the results of thermal investigations with results of X-ray measurements has shown that the ionic character of the chemical bonds is highest for sodium iodate and lowest for sodium chlorate.

Gravimetric determination of copper(II) with p-aminobenzoic acid.

A method has been developed for the gravimetric determination of 20-100 mg of copper(II) with p-aminobenzoic acid. Ag, Hg(II), Pb, Al, Fe(II), Bi, Sb(III) and Sn(II) interfere, but Zn, Co(II), Ni and Cd do not. The precipitate can be weighed after drying at 80-100 degrees , or can be ignited to copper(II) oxide at temperatures above 400 degrees , and weighed in this form.

Electron spin resonance analysis of the redox indicator variamine blue II.

The oxidation of the redox indicator Variamine Blue in an aqueous medium has been studied by the ESR method. The optimum conditions for the formation of the radical have been determined. The spectra have in some cases shown hyperfine splitting, from which conclusions could be drawn for the nature of the oxidation reaction and structure of the oxidized product. The coupling constants have also been determined for the radicals. The correctness of the assumptions for the structure of the radicals has been supported by the simulation of spectra and the investigation of deuterated derivatives.