Manganese dichromate

The preparation of triaryknethane dyes proceeds through several stages formation of the colorless leuco base in acid media, conversion to the colorless carbinol base by using an oxidising agent, eg, lead dioxide, manganese dioxide, or alkah dichromates, and formation of the dye by treatment with acid (Fig. 1). The oxidation of the leuco base can also be accompHshed with atmospheric oxygen in the presence of catalysts. 

Thymoquinone has been prepared directly from thymol by sulfonating and oxidizing the sulfonation mixture with manganese dioxide or potassium dichromate the same process has been successfully applied to carvacrol. The oxidation of sa ts of aminothymol with dichromate, ferric chloride, or nascent bromine also leads to satisfactory yields of thymoquinone. The above procedure is based on the observation that the diazonium salt obtained from aminothymol is almost quantitatively con-... 

The procedure described is that of Wille and Saffer. Propiolaldehyde has also been prepared by the oxidation of propargyl alcohol using ammonium dichromate or manganese dioxide in 10% sulfuric acid. Propiolaldehyde has also been prepared by warming the dimethyl or diethyl acetal with dilute sulfuric acid. ... 

Medium acid baths, pH 4-5 At this acidity a dichromate solution plus sulphate ion as activator is sufficient to deposit chromate films in 30 min or so at room temperature or in a few minutes at boiling point. Unfortunately, a solution of alkali dichromate and alkali sulphate is quite unbuffered, and other substances must be added to give the bath a useful life over the working pH range. Acetates have been used successfully, but salts of aluminium, chromium, manganese and zinc have been more commonly employed. The pH of the solution rises slowly during use until basic chromates or sulphates begin to precipitate. The solution can then be rejuvenated by the addition of chromic or sulphuric acid or acid salts. 

Transition metal ions. Transition metal ions impart color to many of their compounds and solutions, (a) Bottom row (left to right) iron(lll) chloride. copper ll) sulfate, manganese(ll) chloride, cobalt(ll) chloride. Top row (left to right) chromium(lll) nitrate, iron(ll) sulfate, nickel(ll) sulfate, potassium dichromate, (b) Solutions of the compounds in (a) in the order listed above. 

Solids with different structures, (a) Diamond, a network covalent solid, (b) Potassium dichromate. K2 2O7, an ionic solid, (c) Manganese, a metallic solid. 

The above considerations will be illustrated by the simultaneous determination of manganese and chromium in steel and other ferro-alloys. The absorption spectra of 0.001 M permanganate and dichromate ions in 1M sulphuric acid, determined with a spectrophotometer and against 1M sulphuric acid in the reference cell, are shown in Fig. 17.20. For permanganate, the absorption maximum is at 545 nm, and a small correction must be applied for dichromate absorption. Similarly the peak dichromate absorption is at 440 nm, at which permanganate only absorbs weakly. Absorbances for these two ions, individually and in mixtures, obey Beer s Law provided the concentration of sulphuric acid is at least 0.5M. Iron(III), nickel, cobalt, and vanadium absorb at 425 nm and 545 nm, and should be absent or corrections must be made. 

Modification of the burning rates, pressure exponents, and temp coefficients of burning rate of the fluorocarbon composites has been accomplished with copper, lead, tin, sodium, ammonium and potassium fluoborates sodium, potassium, lithium, lead, copper and calcium fluorides potassium and ammonium dichromate lead and zinc stearate cesium carbonate potassium and ammonium sulfate copper chromite oxides of magnesium, copper and manganese boron zinc dust and carbon black (Ref 75)... 

To construct the spontaneous cell reaction, combine the two half-reactions, leaving the permanganate half-reaction as a reduction and reversing the dichromate half-reaction. To match numbers of electrons, multiply the manganese half-reaction by 6 and the chromium half-reaction by 5 ... 

C03-0017. Write correct molecular formulas for aluminum oxide, potassium dichromate, lead(II) nitrate, nitrogen dioxide, sodium sulfate, iodine pentafluoride, manganese(II) acetate, and sodium hypochlorite.. 

Action of chlorine trifluoride causes incandescence [1]. Manganese dioxide catalytically decomposes powerful oxidising agents, often violently. Dropped into cone, hydrogen peroxide, the powdered oxide may cause explosion [2], Either the massive or the powdered oxide explosively decomposes 92% peroxomonosulfuric acid [3], and mixtures with chlorates ( oxygen mixture , heated to generate the gas) may react with explosive violence [4], Cuban pyrolusite can be used in place of potassium dichromate to promote thermal decomposition of potassium chlorate in match-head formulations [5],... 

Quinone may be prepared by the oxidation of aniline with dichromate or manganese dioxide and sulfuric acid.1 This is a more feasible commercial method than the one given. However, the oxidation of hydroquinone is more rapid and convenient and, hence is more desirable for use in the laboratory. Various materials have been oxidized by chemical means to give quinone they are quinic acid,2 hydroquinone,3 benzidine,4 -phenylene-diamine,5 sulfanilic acid,6 / -phenolsulfonic acid,7 arbutin,8 aniline black,9 and the leaves of various plants.10 Quinone is also formed by several other methods by the fermentation of fresh grass 11 by the action of iodine on the lead salt of hydroquin-... 

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). ... 

The oxidation of alcohols to the corresponding aldehydes, ketones or acids certainly represents one of the more important functional group transformations in organic synthesis and there are numerous methods reported in the literature (1-3). However, relatively few methods describe the selective oxidation of primary or secondary alcohols to the corresponding aldehydes and ketones and most of them traditionally use a stoichiometric terminal oxidant such as chromium oxide (4), dichromate (5), manganese oxide (6), and osmium or ruthenium oxides as primary oxidants (7). 

The treatment of polonium(lV) with nitric acid/potassium permanganate under reflux yields a sludge of manganese dioxide which contains all the polonium originally present the valency state is uncertain. Polonium (IV) in weighable amounts is not oxidized by persulfate, ceric salts or chlorine in alkaline solution (12), although trace scale work indicates that both ceric salts and dichromate do oxidize polonium to polonium(VI) (94). 

Other commercially important inorganic chemicals that can be made electrolytically include caustic soda and chlorine, chlorate and perchlorate salts (Chapter 12), potassium dichromate (K2Cr207), manganese dioxide, and potassium permanganate.16... 

Chlorine is nearly always prepared in the laboratory by the action of an oxidizing agent—manganese dioxide, lead dioxide, barium dioxide, potassium dichromate,... 

---