Chromium bromate

Chromium Bromate, Cr(Br03)3, is said to have been obtained by evaporation of the filtrate from a mixture of chromic sulphate and barium bromate. 

A voltaic cell consists of two half-cells. One of the half-cells contains a platinum electrode surrounded by chromium(III) and dichromate ions. The other half-cell contains a platinum electrode surrounded by bromate ions and liquid bromine. Assume that the cell reaction, which produces a positive voltage, involves both chromium(III) and bromate ions. The cell is at 25°C. Information for the bromate reduction half reaction is as follows ... 

Determination of chromium as lead chromate (precipitation from homogeneous solution) Discussion. Use is made of the homogeneous generation of chromate ion produced by the slow oxidation of chromium(III) by bromate at 90-95 °C in the presence of excess of lead nitrate solution and an acetate buffer. The crystals of lead chromate produced are relatively large and easily filtered the volume of the precipitate is about half that produced by the standard method of precipitation. 

The cobalt complex is usually formed in a hot acetate-acetic acid medium. After the formation of the cobalt colour, hydrochloric acid or nitric acid is added to decompose the complexes of most of the other heavy metals present. Iron, copper, cerium(IV), chromium(III and VI), nickel, vanadyl vanadium, and copper interfere when present in appreciable quantities. Excess of the reagent minimises the interference of iron(II) iron(III) can be removed by diethyl ether extraction from a hydrochloric acid solution. Most of the interferences can be eliminated by treatment with potassium bromate, followed by the addition of an alkali fluoride. Cobalt may also be isolated by dithizone extraction from a basic medium after copper has been removed (if necessary) from acidic solution. An alumina column may also be used to adsorb the cobalt nitroso-R-chelate anion in the presence of perchloric acid, the other elements are eluted with warm 1M nitric acid, and finally the cobalt complex with 1M sulphuric acid, and the absorbance measured at 500 nm. 

Hydroxylamine is a powerful reducant, particularly when anhydrous, and if exposed to air on a fibrous extended surface (filter paper) it rapidly heats by aerobic oxidation. It explodes in contact with air above 70°C [1]. Barium peroxide will ignite aqueous hydroxylamine, while the solid ignites in dry contact with barium oxide, barium peroxide, lead dioxide and potassium permanganate, but with chlorates, bromates and perchlorates only when moistened with sulfuric acid. Contact of the anhydrous base with potassium dichromate or sodium dichromate is violently explosive, but less so with ammonium dichromate or chromium trioxide. Ignition occurs in gaseous chlorine, and vigorous oxidation occurs with hypochlorites. 

Chromium trioxide Selenium Fluorine Non-metals Potassium bromate Non-metals Silver(I) oxide Non-metals Sodium peroxide Non-metals... 

The periodinane (10) may also be prepared from o-iodobenzoic acid by oxidation with potassium bromate and then treatment with acetic anhydride18 (see Expt 6.36 for detailed formulation). It should be noted that the organic derivatives of pentacoordinate iodine(v) are termed periodinanes.18b This compound (the systematic name is l,l,l-triacetoxy-2,l-benzoxiodol-3(3//)-one) has found use as an oxidant of primary alcohols to aldehydes and alicyclic ketones to secondary alcohols it is claimed to have advantages over the chromium-based oxidation reagents. 

Write the formulas for the following ionic compounds (a) lithium hydride (b) calcium bromate (c)chromium(II) oxide id) thorium(IV) perchlorate (e) nickel phosphate if) zinc sulfate. 

Oxidants. Hydrogen sulfide ignites on contact with silver bromate,8 bromine pentafluoride,9 mercury(I) bromate,10 lead hypochlorite,11 copper chromate,12 fluorine,13 fuming nitric acid,14 solid sodium peroxide,15 and dry or moist lead oxide.5 16 Dichlorine oxide17 or chlorine trifluoride18 explodes on contact with hydrogen sulfide. Heated chromium trioxide incandesces in a stream of hydrogen sulfide. 

Chinese hamster lung DON cells Sister chromatid exchange, chromosomal aberrations No data + Koshi 1979, Koshi and Iwaski 1983 Lead chromate, chromium trioxide, zinc bromate, calcium chromate, potassium chromate... 

Ganescu et al. used thiocyanato Cr(III)-complexes in the titrimetric and spectrophotometric determination of dipyridamole [16]. For titrimetric analysis of the drug (1.36-27.2 mg), sample solutions (25-50 mL) were acidified with hydrochloric acid and treated with excess of a 3% solution of ammonium dianilinetetrakis (thiocyanato) chromium (III) in aqueous 25% ethanol. The red-violet precipitate was collected and washed, decomposed with NaOH, and the mixture again acidified. The liberated thiocyanate was titrated with potassium permanganate, potassium bromate, or potassium iodate. 

Upon treatment of the filtrate from 1 with sodium nitrite solution, chlorate and bromate are reduced to the simple halides, the presence of which is revealed by the separation of silver chloride and silver bromide respectively. Chromates (which, of course, yield a coloured solution) are simultaneously reduced to chromium(III) salts. 

Ignites on contact with metal oxides (e.g., barium peroxide, chromium trioxide, copper oxide, lead dioxide, manganese dioxide, nickel oxide, silver(I) oxide, silver(II) oxide, sodium peroxide, thallium(III) oxide, mercury oxide, calcium oxide, nickel oxide), oxidants (e.g., silver bromate, heptasilver nitrate octaoxide, dibismuth dichromium nonaoxide, mercury(I) bromate, lead(II) hypochlorite, copper chromate, fluorine, nitric acid, sodium peroxide, lead(IV) oxide), rust, soda-lime + air. Reacts violently with NI3, NF3, p-bromobenzenediazonium chloride, OF2, F2, Cu, CIO, BrFs,... 

Among other kinetic studies in aqueous solutions are those of the reaction of chlorate with vanadium(II) and with chromium (II) °. The reactions of bromate with hydrazoic acid" and with hypophosphite" have been examined. 

IIIC) Kuhnert, L., Pehl, K. W. Bipyridine Complexes of Osmium and Chromium Catalyzing the 1981-2 Oscillating Reaction between Bromate and Malonic Acid. Chem. Phys. Lett. 84 (1) 159-162. 

---