Cupric dichromate

Dissolve 15-0 g. of A.R. barium nitrate and 130 g. of A.R. cupric nitrate trihydrate in 450 ml. of water at 80°. Prepare a solution of sodium chromate by dissolving 89 g. of recrystallised sodium dichromate dihydrate in 200 ml. of water and adding 112 5 ml. of cone, ammonia solution (sp. gr. 0-90). Add the warm solution (80°) of nitrates in a thin stream, with stirring, to the sodium chromate solution (at 25°). Collect the orange precipitate by suction Bltration, wash it with two 50 ml. portions of 5fiter, drain well, and dry at 75-80° for 12 hours powder finely. 

The mechanism and rate of hydrogen peroxide decomposition depend on many factors, including temperature, pH, presence or absence of a catalyst (7—10), such as metal ions, oxides, and hydroxides etc. Some common metal ions that actively support homogeneous catalysis of the decomposition include ferrous, ferric, cuprous, cupric, chromate, dichromate, molybdate, tungstate, and vanadate. For combinations, such as iron and... 

Many oxidizing agents have been used, especially copper sulfate and other cupric salts. Potassium dichromate in acetic acid and manganese dioxide are good oxidants for benzil bis(phenylhydrazone). Nitrous acid has been used for the osazones of acetylated sugars and for phenylglyoxal bis(phenylhydrazone). ... 

Cm++. Information about the activation of hydrogen by Cu++ is derived largely from kinetic measurements on the cupric perchlorate catalyzed hydrogenation of dichromate [Equation (4)]. The rate-law for this reaction is of the form... 

Hydrogen trisulphide is much more easily combustible than the crude parent hydrogen polysulphide. Exposure to light tends to accelerate its decomposition. It slowly reduces concentrated sulphuric acid to sulphur dioxide, whilst on contact with dry silver oxide, cupric oxide, lead dioxide or mercuric oxide, it bursts into explosive combustion,2 a residue of the metallic sulphide being obtained. Many other metallic oxides and most salts bring about a less vigorous decomposition metals in the massive condition only react with it slowly. With potassium permanganate or dichromate the reaction is violent. 

Fia. 16. Typical rate curves for the reactions of dichromate and cupric acetate with hydrogen temperature, 100°, Hs partial pressure, 13.6 atm. (17). 

Figure 16 also shows that the concentration of cupric acetate remained constant as long as dichromate was undergoing reaction. Only when the reduction of dichromate was complete did the cupric acetate react with hydrogen to form cuprous oxide. Apparently the reduction of cupric acetate is not affected by the previous dichromate reaction or by the presence of small amounts of chromic salts in the solution. 

The dependence of the rate of the dichromate reaction on the concentration of cupric acetate provides further support for the catalytic role of the latter. The results in Fig. 17 show that the rate increases in a nearly linear manner with increasing cupric acetate concentration i.e.,... 

The rate of the catalyzed dichromate reaction was measured at temperatures ranging from 80° to 140°. The results were found to give a good Arrhenius plot. The activation energy is 24.6 kcal./mole, in close agreement with the value of 24.2 kcal./mole found for the reaction of cupric acetate itself with hydrogen. 

Discussion The kinetic similarity of the dichromate reduction in the presence of cupric acetate and the reduction of cupric acetate itself support the view that both have the same rate-controlling step. Halpern and co-workers suggested that the rate is determined by a bimolecular process involving one molecule of cupric acetate and one molecule of hydrogen. They have therefore, proposed the following reaction scheme. 

The intermediate precipitate obtained by the reaction of copper nitrate with ammonium dichromate and ammonia has been shown to be Cu(0H)NH4Cr04,122 and the decomposition of the precipitate to give the catalyst to be formulated as in eq. 1.6, by an X-ray diffraction study by Stroupe, although the catalysts obtained by decomposition at sufficiently controlled low temperature (350°C) are amorphous.123 Catalysts previosly used in liquid-phase hydrogenation below 300°C often show crystalline cupric chromite to have been largely reduced to the cuprous chromite... 

Materials. The wool fabric was a plain-weave worsted wool, style 6561, from Burlington Industries. The silk fabric was a degummed silk crepe, style 601, from Testfabrics, Inc. The dyes were >95% pure and were from the following sources alizarin (C. I. Mordant Red 8) from Aldrich Chemical Co. brazilin (C. I. Natural Red 24) from J. T. Baker Chemical Co. and carminic acid (C. I. Natural Red 4) from H. Kohnstamm Co., Inc. The five reagent grade metal salts used were aluminum potassium sulfate, stannous chloride, cupric sulfate, ferrous sulfate, and potassium dichromate from J. T. Baker Chemical Co. 

Copper chromite (Lazier catalyst). Supplier Harshaw (CU-0202P 556-002). For preparation of the catalysC an aqueous solution of barium nitrate and cupric nitrate trihydrate is stirred during addition of a solution of ammonium chromate, prepared from ammonium dichromate and aqueous ammonia. The reddish brown precipitate of copper barium ammonium chromate is washed and dried and decomposed by heating in a muffle furnace at 350-450 . The ignition residue is pulverized, washed with 10% acetic acid, dried, and ground to a fine black powder. 

Anilin may be recognized by the following reactions (1.) With a nitrate and HaSO<, a red color. (3.) Cold HaSOi does not color it alone on addition of potassium dichromate, a fine blue color is produced, which, on dilution with water, passes to violet and, if not diluted, to black. (8.) With calcium hypochlorite, a violet color. (4J Heated with cupric chlorate, a black color. (5.) Heated with mercuric chlorid, a deep crimson color. (0.) In very... 

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