Chromium reagents hexavalent

Each substrate was oxidized to the corresponding carbonyl compounds in good yields. Moreover, the coexisting olefin linkage remained intact upon treatment with the oxodiperoxochromium complex and no epoxy compounds were observed in the reaction mixture. Hexavalent chromium reagents such as anhydrous chromium trioxide and pyridinium... 

Oxidation with hexavalent chromium usually leads to complex product mixtures.641 However, certain Cr(VI) reagents [Cr02(00CCCl3)2,642 Cr03 supported on silica,643 bistriphenylsilyl chromate644], and a Cr(V) complex,645 may be used to form carbonyl compounds. 

Liquid wastes containing hexavalent chromium require reduction of chromium to the trivalent state prior to metal removal. Commonly used reducing agents are sodium metabisulfite, sulfur dioxide, ferrous sulfide, and other ferrous ions (ferrous sulfate, ferrous chloride, or electrochemically generated ferrous ion). All of these reagents create some form of chromium sludge, which must be separated and dewatered before disposal. 

The oxidation of benzene to p-benzoquinone is impractical, because benzoquinone is obtained from other compounds [647. Condensed aromatic hydrocarbons are oxidized to quinones by many reagents [429, 758, 802], most frequently by the compounds of hexavalent chromium [1121] (equation 150). 

Chromotropic acid was applied as a reagent for ultraviolet spectrophotometric determination of hexavalent chromium in water [10]. 

Reactions are usually very rapid and design is based on mass transfer and mixing to distribute the reactant. For most precipitation reagents allow 5 min residence time. If secondary reagents are needed to change the oxidation state of the target species before precipitation then example residence times are arsenic 30 min, hexavalent chromium or iron 20 min. 

Applications of RPC include separation of metalloproteins, such as. metallothionein isoforms and superoxide dismutase [7]. The majority of applications use ion-pair reagents like trifluoroacetic acid or tetraalky-lammonium hydroxides in the mobile phase to increase the retention of ionic compounds, for example, selenoamino acids [20], trivalent and hexavalent chromium [21], or Pt-nucleotide complexes [22]. 

The primary raw materials used in the surface finishing process include surface cleaning agents, metals for hot-dip deposition, fluxes, chemicals for plating and anodizing baths, and treatment reagents for process effluents. The use of effluent chemicals is required to reduce hexavalent chromium to trivalent chromium to allow for the precipitation of heavy metal content and to ionize the cyanide content. 

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