Chromium , hydrogen peroxide

Addition of dilute potassium dichromate(VI) solution, K2Cr207, to a solution of hydrogen peroxide produces chromium peroxide, CrOj, as an unstable blue coloration on adding a little ether and shaking this compound transfers to the organic layer in which it is rather more stable. 

Ammonia, anhydrous Mercury, halogens, hypochlorites, chlorites, chlorine(I) oxide, hydrofluoric acid (anhydrous), hydrogen peroxide, chromium(VI) oxide, nitrogen dioxide, chromyl(VI) chloride, sulflnyl chloride, magnesium perchlorate, peroxodisul-fates, phosphorus pentoxide, acetaldehyde, ethylene oxide, acrolein, gold(III) chloride... 

Hydrogen peroxide Copper, chromium, iron, most metals or their salts, alcohols, acetone, organic materials, flammable liquids, combustible materials... 

Make acid yields coumaUc acid when treated with fuming sulfuric acid (19). Similar treatment of malic acid in the presence of phenol and substituted phenols is a facile method of synthesi2ing coumarins that are substituted in the aromatic nucleus (20,21) (see Coumarin). Similar reactions take place with thiophenol and substituted thiophenols, yielding, among other compounds, a red dye (22) (see Dyes and dye intermediates). Oxidation of an aqueous solution of malic acid with hydrogen peroxide (qv) cataly2ed by ferrous ions yields oxalacetic acid (23). If this oxidation is performed in the presence of chromium, ferric, or titanium ions, or mixtures of these, the product is tartaric acid (24). Chlorals react with malic acid in the presence of sulfuric acid or other acidic catalysts to produce 4-ketodioxolones (25,26). 

Chromium (ITT) can be analy2ed to a lower limit of 5 x 10 ° M by luminol—hydrogen peroxide without separating from other metals. Ethylenediaminetetraacetic acid (EDTA) is added to deactivate most interferences. Chromium (ITT) itself is deactivated slowly by complexation with EDTA measurement of the sample after Cr(III) deactivation is complete provides a blank which can be subtracted to eliminate interference from such ions as iron(II), inon(III), and cobalt(II), which are not sufficiently deactivated by EDTA (275). 

When hydrogen peroxide is added to an acid solution of Cr(VI), a deep blue color, iadicating the formation of chromium (VI) oxide diperoxide [35262-77-2] is observed. This compound is metastable and rapidly decomposes to Cr(III) and oxygen at room temperature. The reaction... 

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

The final solution should be checked for absence of free cyanide. The hypochlorite or CI2 + NaOH method is by far the most widely used commercially (45). However, other methods are oxidation to cyanate using hydrogen peroxide, o2one, permanganate, or chlorite electrolysis to CO2, NH, and cyanate hydrolysis at elevated temperatures to NH and salts of formic acid air or steam stripping at low pH biological decomposition to CO2 and N2 chromium... 

Concentration Effects. The reactivity of ethyl alcohol—water mixtures has been correlated with three distinct alcohol concentration ranges (35,36). For example, the chromium trioxide oxidation of ethyl alcohol (37), the catalytic decomposition of hydrogen peroxide (38), and the sensitivities of coUoidal particles to coagulation (39) are characteristic for ethyl alcohol concentrations of 25—30%, 40—60%, and above 60% alcohol, respectively. The effect of various catalysts also differs for different alcohol concentrations (35). 

Again, as with pyridopyrimidines, the main reaction is oxidation of di- or poly-hydro derivatives to fully aromatic structures, often merely by air or oxygen. In some cases the reagent of choice is mercury(II) oxide, whilst other reagents used include sulfur, bromine, chloranil, chromium trioxide-acetic acid, hydrogen peroxide, and potassium ferricyanide, which also caused oxidative removal of a benzyl group in the transformation (306) (307)... 

Ammonia can also react violently with a large selection of chemicals including ethylene oxide, halogens, heavy metals, and oxidants such as chromium trioxide, dichlorine oxide, dinitrogen tetroxide, hydrogen peroxide, nitric acid, liquid oxygen, and potassium chlorate. 

Fora filter colorimeter use a blue filter (maximum transmission 400-420 nm) a wavelength of 410 nm is employed for a spectrophotometer. In the latter case, the effect of iron, nickel, chromium(III), and other coloured ions not reacting with hydrogen peroxide may be compensated by using a solution of the sample, not treated with hydrogen peroxide, in the reference cell. 

Chromium causes various accidents with sulphur dioxide or nitrogen oxide (incandescence), carbon dioxide (with which it forms explosive suspensions), hydrogen peroxide (with which it detonates at ambient temperature) and ammonium nitrate (with which it detonates when it is heated to 200 C). 

Note that in these three examples involving hydrogen peroxide, chromium trioxide and sodium nitrite, dangerous reactions have been described for carboxyiic acids (see on p.316-317). They all referred to the three following systems acetic acid-/hydrogen peroxide, acetic acid/chromium trioxide and o-phthalic acid/sodium nitrite. One can ask oneself whether the same reactions did not take place after the acetic and phthalic anhydride hydrolysis. 

Chlorine dioxide Copper Fluorine Hydrazine Hydrocarbons (benzene, butane, propane, gasoline, turpentine, etc) Hydrocyanic acid Hydrofluoric acid, anhydrous (hydrogen fluoride) Hydrogen peroxide Ammonia, methane, phosphine or hydrogen sulphide Acetylene, hydrogen peroxide Isolate from everything Hydrogen peroxide, nitric acid, or any other oxidant Fluorine, chlorine, bromine, chromic acid, peroxide Nitric acid, alkalis Ammonia, aqueous or anhydrous Copper, chromium, iron, most metals or their salts, any flammable liquid, combustible materials, aniline, nitromethane... 

See Bromine pentafhioride Hydrogen-containing materials Chromium trioxide Acetic acid Hydrogen peroxide Acetic acid Potassium permanganate Acetic acid Sodium peroxide Acetic acid... 

Bromine trifluoride Solvents Chromium trioxide Acetone Chromyl chloride Organic solvents Dioxygen difluoride Various materials Hydrogen peroxide Acetone... 

See Chromium trioxide Acetic anhydride Hydrogen peroxide Acetone, etc. 

MRH Ammonium nitrate 3.97/84, chromium trioxide 3.01/81, hydrogen peroxide 6.36/68, nitric acid 5.84/61, potassium dichromate 1.59/tr., sodium chlorate 6.07/69, sodium nitrate 3.18/68... 

Except for Prussian blue activity in hydrogen peroxide, reduction has been shown for a number of transition metal hexacyanoferrates. The latter were cobalt [151], nickel [152], chromium [150], titanium [153], copper [154], manganese [33], and vanadium [28] hexacyanoferrates. However, as was shown in review [117], catalytic activity of the mentioned inorganic materials in H202 reduction is either very low, or is provided by impurities of Prussian blue in the material. Nevertheless, a number of biosensors based on different transition metal hexacyanoferrates have been developed. 

M.S. Lin, T.F. Tseng, and W.C. Shih, Chromium(III) hexacyanoferrate(II)-based chemical sensor for the cathodic determination of hydrogen peroxide. Analyst 123, 159-163 (1998). 

Dubovenko et al. [180] used chemiluminescence to determine total chromium in brines. The method is based on the enhancement of the chemiluminescence by chromium in the reaction of 4-(diethylamino) phthalhydrazide with hydrogen peroxide. The detection limit is 0.025 pg/1 of chromium, and the chemiluminescence is directly proportional to chromium concentrations in the range 5 x 10 10 to 10 6 M. 

Copper(II) sulfate Cumene hydroperoxide Cyanides Cyclohexanol Cyclohexanone Decaborane-14 Diazomethane 1,1-Dichloroethylene Dimethylformamide Hydroxylamine, magnesium Acids (inorganic or organic) Acids, water or steam, fluorine, magnesium, nitric acid and nitrates, nitrites Oxidants Hydrogen peroxide, nitric acid Dimethyl sulfoxide, ethers, halocarbons Alkali metals, calcium sulfate Air, chlorotrifluoroethylene, ozone, perchloryl fluoride Halocarbons, inorganic and organic nitrates, bromine, chromium(VI) oxide, aluminum trimethyl, phosphorus trioxide... 

Ethyl sulfate Flammable liquids Fluorine Formamide Freon 113 Glycerol Oxidizing materials, water Ammonium nitrate, chromic acid, the halogens, hydrogen peroxide, nitric acid Isolate from everything only lead and nickel resist prolonged attack Iodine, pyridine, sulfur trioxide Aluminum, barium, lithium, samarium, NaK alloy, titanium Acetic anhydride, hypochlorites, chromium(VI) oxide, perchlorates, alkali peroxides, sodium hydride... 

Methyl methacrylate 4-Methylnitrobenzene 2- Methylpyridine Methylsodium Molybdenum trioxide Naphthalene 2-Naphthol Air, benzoyl peroxide Sulfuric acid, tetranitromethane Hydrogen peroxide, iron(II) sulfate, sulfuric acid 4-Chloronitrobenzene Chlorine trifluoride, interhalogens, metals Chromium trioxide, dinitrogen pentaoxide Antipyrine, camphor, phenol, iron(III) salts, menthol, oxidizing materials, permanganates, urethane... 

Chromox [Chromium oxidation] A process for destroying organic pollutants in aqueous wastes by oxidation with hydrogen peroxide, catalyzed by Cr6+. Developed by British Nuclear Fuels in 1995, originally for use in nuclear reprocessing. 

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