Selenium gaseous metal

Certain elements (such as arsenic, antimony, mercury, selenium, and tin) can, after producing the soluble digest of the polymer, be converted to gaseous metallic hydrides by reaction of the digest with reagents such as stannous chloride or sodium borohydride ... 

We have already noted that the properties of the elements in Group VI show the characteristic trends that we have come to expect on descending a Group. The elements become more metallic in character oxygen is a covalently bonded gaseous diatomic molecule sulfur is a solid containing Sg molecules and is an insulator selenium (non-metal) and tellurium (semi-metal) are semiconductors with polymeric structures polonium is a metal. The compounds of selenium, tellurium and pollonium also illustrate the inert pair effect and a tendency to higher coordination numbers. 

Dry chlorine reacts with most metals combustively depending on temperature alurninum, arsenic, gold, mercury, selenium, teUerium, and tin react with dry CI2 in gaseous or Hquid form at ordinary temperatures carbon steel ignites at about 250°C depending on the physical shape and titanium reacts violendy with dry chlorine. Wet chlorine is very reactive because of the hydrochloric acid and hypochlorous acid (see eq. 37). Metals stable to wet chlorine include platinum, silver, tantalum, and titanium. Tantalum is the most stable to both dry and wet chlorine. 

Gas chromatography and mass spectroscopy (GC/MS) of inorganic and organometallic compounds, 18 273-276 Gaseous hydroxides, 5 215-258 dimerization of, 5 224 mass spectrometric study of, 5 220-225 metalic, 5 220 nonmetallic, 5 217-220 study of in oxyhydrogen flame, 5 225-226 types of, 5 215-217 Gases, see also specific substances high ternperamre species from, 14 137-139 thermal decomposition of, 17 90-93 Gas phase electron resonance spectra, of sulfur and selenium fluorides, 24 190... 

Sulphur and selenium unite when warmed with the metal 51 when sulphur is triturated with sodium, the reaction proceeds with explosive violence which can be moderated by dilution with common salt. Under boiling toluene, sulphur forms the trisulphide Na2S3. Selenium forms the monoselenide, Na2Se, when heated with sodium. Sodium is attacked by hydrogen sulphide at ordinary temp., and at the fusion point the metal bums in the gas. Gaseous ammonia reacts readily with sodium, and liquid ammonia forms blue soln.—the so-called alkali-ammoniums. 

The metal balance for all the elements analyzed by mass spectrometry is good, but on the average shows a negative imbalance of 20%. Metals showing high imbalance, i.e., mercury, arsenic, and selenium, probably were in the gaseous state at the sample points. For example, a precipitator outlet sample of mercury showed a flow of 0.02 g min"1. At this sampling point the particulates are much cooler than the fly ash at the precipitator inlet. 

Some metals, for example, arsenic and selenium, are difficult to analyze by atomic absorption because their analytical wavelengths are subject to considerable interference. These metals, however, are readily converted to gaseous hydrides by treatment with strong reducing reagents such as sodium borohydride. Since the hydrides can be readily separated from the sample matrix, interferences are much reduced. A typical hydride generation AAS is... 

A somewhat similar theory10 postulates the formation of colloidal lead by the decomposition of lead tetraethyl, which deposits on sharp points, edges, and projections in the cylinder which would otherwise aid reaction to an extent that a detonation wave would result. The theory fails to explain the action of organic amines, of di- and tetravalent. selenium, of the colloidal metal sols, and fails to account for the immediate recurrence of knocking when the antiknock dope is discontinued in the gasoline feed. However, tubes coated with lead oxide have been found to reduce the oxidation of hexane more than lead tetraethyl vapors.1158 On the basis of this finding the hypothesis was advanced that oxidation occurs to some extent prior to compression and at the first contact of the gaseous mixture with the hot walls, aud that in the presence of the lead... 

Chromium trioxide and certain other chromium(VI) compounds are useful as strong oxidizing agents in the laboratory, but appropriate precautionary measures should be taken when conducting these reactions. Chromium trioxide has been reported to react violently with a variety of substances, including readily oxidized organic compounds such as acetone, acetaldehyde, methanol, ethanol, diethyl ether, ethyl acetate, acetic acid, and DMF, and violent reactions may also occur on reaction with alkali metals, gaseous ammonia, phosphorus, and selenium. 

Using sodium borohydride, selenium ions are reduced to selenium hydride, transferred to a heated quartz cuvette with the aid of a current of inert gas, decomposed thermally, and the absorption of the atoms is measured in the beam of an atomic-absorption spectrometer. In the hydride technique, the element which is to be determined is volatilized as a gaseous hydride and separated off from the matrix. Interferences may occur if there is a considerable excess of elements such as antimony, arsenic, tin, bismuth, mercury, or tellurium, which may also be volatilized using this technique. Above all, heavy metals such as copper and nickel have a disturbing effect during the hydride formation itself. These interferences may be diminished by adding 300 mg of solid 2-pyridine aldoxime to the solution for measurement. 

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