Manganese chromates

Manganese Chromates.—The normal salts have not been isolated. When an alkali chromate is added to a solution of a manganese salt, some of the manganese undergoes oxidation, and the brownish-black... 

The existence of most of the double salts wluch have been described in the literature must be considered as extremely doubtful, but by adding manganous chloride to a concentrated solution of potassium chromate, potassium manganese chromate, K2Mn(Cr0j)2.2H20, has been obtained by Groger as a red crystalUne precipitate. 

Diseases of the lungs caused by dusts include silicosis (from quartz dust), asbestosis (from asbestos) and cancer. Adverse effects on tite blood and blood-forming system can be caused by lead, cadmium oxide, manganese, chromates, arsenic, insecticides, and radioactive dusts. 

Bismuth chromates group Calcium chromates group Copper chromates group Iron chromates group Lead chromates group Zinc chromates group Barium chromate(VI) Barium potassium chromate Cadmium chromate Crocoite Manganese chromate Mercury chromate Silver chromate Strontium chromate Thallium chromate Tin chromate... 

Copper chromate oxide hydrate Cobalt chromate Iron dichromate Iron chromate hydroxide Manganese chromate hydrate Silver chromate Thallium chromate Titanium chromate Cadmium chromate Cadmium chromate hydroxide Mercury chromate Zinc dichromate hydrate Zinc chromate(VI) hydroxide Zinc sodium chromate Zinc potassium chromate... 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

Oxidation. Citric acid is easily oxidized by a variety of oxidizing agents such as peroxides, hypochlorite, persulfate, permanganate, periodate, hypobromite, chromate, manganese dioxide, and nitric acid. The products of oxidation are usually acetonedicarboxyhc acid (5), oxaUc acid (6), carbon dioxide, and water, depending on the conditions used (5). 

For prestressed concrete, either high-tensile steel wires or occasionally bars of steel alloy containing manganese and silicon, can be used. Galvanised wires may also be used for prestressed concrete, but it is recommended that they be chromated before use. 

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. 

Reaction between arsenic(III) and chromate may induce the oxidation of several acceptors, such as manganese(II), iodide and bromide ions. 

In the presence of manganese(II) ions the rate of oxidation of H2R by chromic acid decreases . Under favourable experimental conditions (high concentration of alcohol and low concentration of chromate) the diminution of rate is about 50 % which is in accordance with results listed in Table 6, according to which ci = 0.5. The inhibiting effect of manganese(II) on the oxidation of H2R can be explained by reaction (23) followed by step (24). Therefore the induced oxidation of manganese(II) can be described by reactions (26), (23) and (24). 

This scheme accounts for both the induced oxidation of iodide (where ci = 2) and that of manganese(ri) (where ci = 0.5) without including step (19). Furthermore it can be seen that in the presence of iodide the rate of disappearence of chromate will not be altered, whilst the rate of oxidation of arsenic(III) will be reduced to one-third of its original value, as found experimentally. 

Reduced Cr(III) may be re-oxidized into Cr(VI) by Mn oxides in soils. Chung et al. (2001) reported that native Cr(III) in subsurface materials of arid and semi-arid regions can be oxidized to soluble chromate by native manganese oxides. If subsurface materials contain a low content of Mn oxides, the re-oxidization of reduced Cr(III) is not significant. 

Mixture % Manganese, Mn % Lead chromate 1 Barium chromate Burning rate, cm /second... 

The translation of Karsten s Tables contains in del Rio s handwriting the following note of presentation To the Philosophical Society of Philadelphia, this work is most respectfully dedicated, which contains four new discoveries—the sulphur of manganese, acknowledged by Mr. Proust to have been discovered by me—the sous-chromate of lead. . . the hydrophanous copper. . . also the lavender. . . copper ore. This note... 

Method No 215. Delay Composition for Defay Elements T6E4 and T5E3- Specification MIL-D-46483B(MU)(1964) states that it consists of Lead Chromate (and/or Barium Chromate) and powdered Manganese, but does not list the percentage of components. Procedures were changed by Engineering Order EO-PA-52713-2 (1968)... 

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