Selenium chloride analysis

In all 28 parameters were individually mapped alkalinity, aluminum, antimony, arsenic, barium, boron, bromide, cadmium, calcium, chloride, chromium, conductivity, copper, fluoride, hardness, iron, lead, magnesium, manganese, nitrate, pH, potassium, selenium, sodium, sulphate, thallium, uranium, and zinc. These parameters constitute the standard inorganic analysis conducted at the DENV Analytical Services Laboratory. 

Chemical vaporisation. Some elements (such as arsenic, bismuth, tin and selenium) are difficult to reduce in a flame when they are in higher oxidation states. For these atoms, the sample is reacted with a reducing agent prior to analysis (sodium borohydride or tin chloride in acidic media) in a separate vessel. The volatile hydride formed is carried by a make-up gas into a quartz cell placed in the flame (Fig. 14.10). 

By the action of hydrazine hydrate on a dilute solution of selenic acid, hydrazine hydrogen selenate may be obtained as a colourless compound which is not decomposed by boiling water, but which, when dry, explodes with great readiness when subjected to heat, to shock, or to fumes of hydrogen chloride. For this reason, before hydrazine hydrate is used in the analysis of selenium compounds (see p. 307), it is essential that selenic acid and selenates should be reduced to selenites by means of hydrochloric acid.3... 

The discoloring is likely to be caused by the photoreduction of silver chloride and/or silver phosphate in the skin. X-ray dispersive analysis of skin and other tissues reveals that the granules consist of silver complexed with sulfur and/or selenium. The photoreduced deposits are not removed by the body, and there are no clinical means of removing them. 

Samarium (III) nitrate, analysis of anhydrous, 6 41 Selenic acid, crystalline, 3 137 Selenides, precipitation of pure metallic, from solutions of hydrogen selenide, 2 185 Selenium, red and gray, 1 119 Selenium (II) chloride, formation of, by selenium(IV) chloride, 6 127... 

Selenium(IV) chloride, 5 125 analysis of, 6 126 compound with aluminum chloride, 5 127... 

Phillips and Timms [599] described a less general method. They converted germanium and silicon in alloys into hydrides and further into chlorides by contact with gold trichloride. They performed GC on a column packed with 13% of silicone 702 on Celite with the use of a gas-density balance for detection. Juvet and Fischer [600] developed a special reactor coupled directly to the chromatographic column, in which they fluorinated metals in alloys, carbides, oxides, sulphides and salts. In these samples, they determined quantitatively uranium, sulphur, selenium, technetium, tungsten, molybdenum, rhenium, silicon, boron, osmium, vanadium, iridium and platinum as fluorides. They performed the analysis on a PTFE column packed with 15% of Kel-F oil No. 10 on Chromosorb T. Prior to analysis the column was conditioned with fluorine and chlorine trifluoride in order to remove moisture and reactive organic compounds. The thermal conductivity detector was equipped with nickel-coated filaments resistant to corrosion with metal fluorides. Fig. 5.34 illustrates the analysis of tungsten, rhenium and osmium fluorides by this method. 

The Methylene (and Ethylene) Blue method has been applied in determinations of sulphur in plants [86], biological materials [87], waters [12,88], air [5,12,16,20], hydrocarbons [89], iron alloys [90,91], cobalt and zirconium [91], titanium [92], thallium and its halides [93], arsenic [94], selenium [95], and various reagents (including barium chloride) [14]. Flow-injection analysis has been applied in the determination of sulphur by the Methylene Blue method [96]. 

One of the more successful co-depositions of GIGS was reported by Cahxto et al. [110], who used a ratio of selenium and copper ions in the deposition bath similar to that employed by Ghassaing et al., but chose a chloride-based supporting electrolyte to stabilize the Ga(III) ions. These authors achieved a Ga/(Ga-n In) ratio of 0.2 in the precursor film as indicated in the XRD analysis of the aimealed semiconductor by the shift of the (112) peak from d = 3.348 to 3.314 A. The best device had an efficiency of 6.2%. Bhattacharya et al. also used similar routes to co-deposit GIGS and incorporated additional Ga into the deposit by non-electrochemical means [111]. 

A wide variety of inorganic materials have been used to precipitate or collect trace metals from solution. The most direct approach is a cementation process, which is one that removes the trace pollutants from solution by reduction with a metal and plating onto that metal surface. Although this process may be slow, the filtration is usually quick, since decantation is often sufficient. Finely divided cadmium extracts copper, selenium, and mercury from nitric and sulfuric acid solutions (66). When copper was used to preconcentrate mercury from water or biological fluids prior to atomic absorption analysis, the detection limit was 1-2 X 10 g (67, 68). Iron (69), zinc (70), and tungsten (71), as metals, have also been used to obtain a deposit of several trace metals from aqueous systems as dilute as 10 ppb for subsequent analysis. Elemental tellurium can be produced in solution by reduction using tin(II) chloride or sulfur dioxide, and coprecipitates silver (72) and selenium (73). Granulated silicon-metal alloys were used to remove metal ions from water and brine by reduction as well (74, 75). 

Precipitation of lead dioxide by anodic deposition on a platinum gauze electrode Is a standard method of separation and determination for lead (H3) In the standard procedure the presence of chloride Ion, mercury, arsenic, tellurium, selenium and phosphorus prevent the complete deposition of lead, while bismuth, tin, antimony, and manganese co-deposit. The use of controlled potential deposition and com-plexlng agents make this separation method much more selective (l4). The eleotroanalytical method has been Important for lead analysis and is discussed In detail In section IV-10,... 

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