Chromic oxide, toxicity

Aluminium alkyls Chromic oxide Alkylations/Grignard reactions Acute thermal burns, lung damage Cr may be converted to the more toxic and carcinogenic Cr ... 

Most of the CL6 found in nature is a result of domestic and industrial emissions (Steven et al. 1976). Interaction of +6 chromic oxide, dichromate, or chromate compounds with organic compounds can result in reduction to the comparatively less toxic trivalent form (Taylor and Parr 1978). 

Ivankovic S, Preussmann R. 1975. Absence of toxic and carcinogenic effects after administration of high doses of chromic oxide pigment in subacute and long-term feeding experiments in rats. Food Cosmet Toxicol 13 347-351. 

ARSENOLITE or ARSENOUS ACID or ARSENOUS ACID ANHYDRIDE or ARSENOUS ANHYDRIDE (1327-53-3) AS2O3 Noncombustible solid. Reacts, possibly violently, with acids, aluminum, aluminum chloride, chlorine trifluoride, chromic oxide, fluorine, fluorides, halogens, hydrogen fluoride, mercury, oxygen fluoride, phosphorus pentoxide, rubidium acetylide, sodium chlorate, sodium hydroxide, sulfiiric acid, tannic acid, zinc iron in solution. Contact with acids or acid mists releases toxic and flammable arsine gas. The aqueous... 

Overall, chromium is the twenty-first most abundant element in Earth s crust. Itis usually found in the +2 (e.g., CrO), -1-3 (e.g., Cr203), or -1-6 (e.g., K2Cr20y) oxidation states, with chromic oxide, Cr203, being the ninth most abundant compound in Earth s crust. While chromium is considered a necessary micronutrient in human diets, many of its compounds are quite toxic. This is especially true of chromium in the -1-6 oxidation state, with compounds such as K2Cr20y being identified as carcinogens. Thus chromium compounds should be handled carefully. 

EXPLOSION and FIRE CONCERNS combustible solid NFPA rating (NA) reacts to form explosive products with metal amides contact with acids may cause formation of poisonous hydrogen selenide gas incompatible or reacts violently with barium carbide, bromine pen-tafluoride, chromic oxide, fluorine, lithium carbide, lithium silicon, metals, nickel, sodium, nitric acid, nitrogen trichloride, oxygen, potassium, potassium bromate, rubidium carbide, zinc, silver bromate, uranium, strontium carbide, and thorium carbide toxic gases and vapors may be released in a fire involving selenium, sodium selenite, sodium selenate, and selenium dioxide use water for firefighting purposes. 

The predominant inert marker in fish studies is chromic oxide. However, chromic oxide does not only satisfy the criteria listed above, but also is not always totally recovered in the faeces [79]. In addition, chromium may be toxic even at low concentrations and, in some cases, allergenic to man, which makes it necessary to take extra care during the manufacture, use, and analysis of feeds and faeces with high concentrations of chromium. 

Most of the Cr+ foimd in nature is a result of domestic and industrial emissions. Interaction of -1-6 chromic oxide, dichromate, or chromate compoimds with organic compoimds can result in reduction to the comparatively less toxic trivalent form. Chromium compoimds interact synergistically or antagonistically with many chemicals. For example, potassium dichromate administered by subcutaneous injection potentiated the effects of mercuric chloride, citrinin, and hexachloro-1,3-butadiene on rat kidneys. Chromium effects were lessened by ascorbic acid and vitamin E, and A -acetyl cysteine was effective in increasing urinary excretion of chromium in rats. 

The primary routes of entry for animal exposure to chromium compounds are inhalation, ingestion, and, for hexavalent compounds, skin penetration. This last route is more important in industrial exposures. Most hexavalent chromium compounds are readily absorbed, are more soluble than trivalent chromium in the pH range 5 to 7, and react with cell membranes. Although hexavalent compounds are more toxic than those of Cr(III), an overexposure to compounds of either oxidation state may lead to inflammation and irritation of the eyes, skin, and the mucous membranes associated with the respiratory and gastrointestinal tracts. Skin ulcers and perforations of nasal septa have been observed in some industrial workers after prolonged exposure to certain hexavalent chromium compounds (108—110), ie, to chromic acid mist or sodium and potassium dichromate. 

Synthesis of aldehydes from alcohols is an important transformation in several applications. In small scale oxidations still chromic acid is being used as a stoichiometric oxidant of alcohols, which leads to a large amount of toxic waste and it is also expensive. Catalytic routes have been reported using palladium catalyst [18], or TEMPO (see also Figure 15.13) as a radical catalyst for the oxidation of alcohols [19], or combinations of TEMPO and copper [20] related work is mentioned in the references of these articles. The mechanism of... 

Chromium occurs in soils predominantly as the immobile - -3 chromic cation (Cr ), but may be oxidized to or added as +6 chromate species (Cr04, HCr04 ). Chromate is weakly sorbed on soils and is highly toxic to... 

See under COPPER AND ITS SALTS Lead Dlchromate, PbCr207, mw 423.23 brick red or brn-red,amorph or cryst pdr mp( ) decomp by w sol in ale or alkalies(Ref 5) can be prepd by treating Pb chromate with a coned soln of chromic acid or by other methods (Ref 1). It is a powerful oxidizer and reacts vigorously when heated with reducing materials when heated to decompn, it emits highly,toxic fumes of lead(Ref 4) can probably be used for the same purposes as PbCrO, namely in pyrotechnics... 

Water spots can be removed with an oxidizer such as any substitute for chromic acid (see Sec. 4.1.9). Do not use chromic acid because it is a toxic waste. 

Exposure to inorganic chemicals in the workplace has been traditionally evaluated using elemental analysis. However, in recent years some attention has been given to the toxic effects of specific compounds rather than elements, e.g., chromic acid ( ), nickel subsulfide Q), zinc oxide (4.), and sodium hydroxide (5.). It is therefore important that the occupational health chemist develop the capability to identify and quantitate chemical compounds. To this end, X-ray powder diffraction (XRD) is a unique tool for... 

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