Oxidation potassium chromate

The effects of various metal oxides and salts which promote ignition of amine-red fuming nitric acid systems were examined. Among soluble catalysts, copperQ oxide, ammonium metavanadate, sodium metavanadate, iron(III) chloride (and potassium hexacyanoferrate(II) with o-toluidine) are most effective. Of the insoluble materials, copper(II) oxide, iron(III) oxide, vanadium(V) oxide, potassium chromate, potassium dichromate, potassium hexacyanoferrate(III) and sodium pentacyanonitrosylferrate(II) were effective. 

In neutral solution, the indicator is potassium chromate(VI). In acid solution the CrOj" ion changes to CrjO (p. 378). and since silver dichromatefVI) is soluble, chromate(VI) is not a suitable indicator other methods can be used under these conditions. (In alkaline solution, silverfl) oxide precipitates, so silver(I) nitrate cannot be used under these conditions.)... 

Sihcon carbide is comparatively stable. The only violent reaction occurs when SiC is heated with a mixture of potassium dichromate and lead chromate. Chemical reactions do, however, take place between sihcon carbide and a variety of compounds at relatively high temperatures. Sodium sihcate attacks SiC above 1300°C, and SiC reacts with calcium and magnesium oxides above 1000°C and with copper oxide at 800°C to form the metal sihcide. Sihcon carbide decomposes in fused alkahes such as potassium chromate or sodium chromate and in fused borax or cryohte, and reacts with carbon dioxide, hydrogen, ak, and steam. Sihcon carbide, resistant to chlorine below 700°C, reacts to form carbon and sihcon tetrachloride at high temperature. SiC dissociates in molten kon and the sihcon reacts with oxides present in the melt, a reaction of use in the metallurgy of kon and steel (qv). The dense, self-bonded type of SiC has good resistance to aluminum up to about 800°C, to bismuth and zinc at 600°C, and to tin up to 400°C a new sihcon nitride-bonded type exhibits improved resistance to cryohte. 

Cathylates are stable to oxidation with potassium chromate in acetic acid and with A-bromoacetamide, acetylation and formylation with 85 % formic acid at room temperature. They are cleaved by bases to give the parent alcohol, carbon dioxide and ethanol. 

C19-0107. Potassium chromate, K2 CrOq, dissolves in acidic solution to generate strongly oxidizing Cr2 07 ... 

Ammonium chromate Potassium chromate Chromium potassium sulphate Lithium chromate (yitomium trinitrate Sodium chromate Clsomium fV )oxide Lead chromate Strontium chromate 2nc ctvomate... 

Bentley and Murray (201) reported another method for synthesis of protopine alkaloids allocryptopine (392) and cryptopalmatine (395) from tetrahydroprotoberberine /V-oxides (35a and 400) through oxidative rearrangement with potassium chromate (Scheme 73). 

DeNOx (1) A Denox process for removing nitrogen oxides from the gaseous effluents from nitric acid plants. The oxides are reduced with ammonia, over a catalyst containing potassium chromate and ferric oxide. Developed by Didier Werke in the 1980s. 

Ammonium nitrate Ammonium perchlorate Barium chlorate (hydrate) Barium chromate Barium nitrate Barium peroxide Iron oxide Iron oxide Lead chromate Lead oxide (red lead) Lead peroxide Potassium chlorate Potassium nitrate Potassium perchlorate Sodium nitrate Strontium nitrate... 

Another important factor is the thermal stability and heat of decomposition of the oxidizer. Potassium chlorate mixtures tend to be much more sensitive to ignition than potassium nitrate compositions, due to the exothermic nature of the decomposition of KCIO 3. Mixtures containing very stable oxidizers - such as ferric oxide (Fe 2O 3) and lead chromate (PbCrO 4) - can be quite difficult to ignite, and a more-sensitive composition frequently has to be used in conjunction with these materials to effect ignition. 

W. Ostwald considers that the presence of the highly oxidized salts—iodates and perchlorates—shows that the deposits were formed in an atm. highly charged with ozone. H. Guyard says the yellow coloration of some samples is due to the presence of potassium chromate and the violet to manganese nitrate. The... 

Preparation of Potassium Chromate. (Perform one experiment on each table.) Melt a mixture of 1 g of potassium carbonate, 1 gof potassium hydroxide, and 2 g of potassium nitrate in an iron crucible by heating with the flame of a burner. While stirring the melt with an iron wire, introduce 1 g of finely comminuted chromite or -0.8 g of chromium oxide into the crucible. Roast the mixture for 5-10 minutes on a blowpipe. Treat the cooled melt with water. Filter the solution and evaporate it until a crystalline film appears. What is the composition of the formed crystals Why was potassium carbonate introduced into the reaction Write the equation of the reaction. 

Methyl 3-Carbethoxyoxy-7-keto-12a-hydroxycholanate.79 A solution of 4 g (8.6 mmoles) of crude methyl 3-carbethoxyoxycholate in 50 ml of acetic acid containing 10 g of sodium acetate trihydrate is treated gradually with a solution of 3 g (0.015 mole) of potassium chromate in 8 ml of water with shaking. After 10 hr at 25° the solution is diluted with water and the product collected by filtration to afford 3.9 g (97%) of methyl 3-carbethoxyoxy-7-keto-12a-hy-droxycholanate, mp 150-158°. Crystallization from methanol gives hard, compact needles or rods mp 157-158° [a]D25 41°. The same substance is also obtained (93 % yield) by conducting the above oxidation in the absence of sodium acetate but stopping the reaction after 6-7 hr. 

Several, different, electrochemical oxidations of 26 to 27 have been reported. Using a variety of electrodes (copper, Monel metal, nickel, or silver), 26 was oxidized in aqueous potassium hydroxide solution containing potassium chromate or potassium permanganate, to afford 27 in 70-85% yield.118,119 This electrochemical oxidation has been conducted in aqueous, alkaline solution in the presence of a surfactant, but with added metal catalyst, to give 27 in 85-95% yield.120 Alternatively, the oxidation has been performed by using an anode on which nickel oxide was deposited. This anode, in a solution of 26 at pH >9, with or without nickel salts, afforded 27 in >90% yield.121 A number of additional publications described122-140 other modifications of the... 

Lead chromate Sulfur Lead(II) chlorite Non-metals Phosphorus(III) oxide Potassium bromate Non-metals Potassium chlorate Charcoal, etc., or Non-metals Potassium chlorite Sulfur Potassium perchlorate Sulfur Potassium permanganate Non-metals Silver bromate Sulfur compounds Silver chlorite Hydrochloric acid, etc. 

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