Chromates, alkali metal

I carbonates Co-Na, Co-K, Ni-Na, Ni-K nitrates Zn-alkali metals sulphates (schoenites) Mg-Na carbonates Al-K, Ce-Na nitrates rare earth-alkali metals sulphates (alums) Me111-alkali metals carbonates Ce-alkali metals nitrates Ce-alkali metals sulphates U-alkali metals alkali metals vanadates alkali metal chromates, Ag chromate, alkali metal molybdates and tungstates... 

The chromates of the alkali metals and of magnesium and calcium are soluble in water the other chromates are insoluble. The chromate ion is yellow, but some insoluble chromates are red (for example silver chromate, Ag2Cr04). Chromates are often isomorph-ous with sulphates, which suggests that the chromate ion, CrO has a tetrahedral structure similar to that of the sulphate ion, SO4 Chromates may be prepared by oxidising chromium(III) salts the oxidation can be carried out by fusion with sodium peroxide, or by adding sodium peroxide to a solution of the chromium(IIl) salt. The use of sodium peroxide ensures an alkaline solution otherwise, under acid conditions, the chromate ion is converted into the orange-coloured dichromate ion ... 

Hydrazine Alkali metals, ammonia, chlorine, chromates and dichromates, copper salts, fluorine, hydrogen peroxide, metallic oxides, nickel, nitric acid, liquid oxygen, zinc diethyl... 

Compounds of Tl have many similarities to those of the alkali metals TIOH is very soluble and is a strong base TI2CO3 is also soluble and resembles the corresponding Na and K compounds Tl forms colourless, well-crystallized salts of many oxoacids, and these tend to be anhydrous like those of the similarly sized Rb and Cs Tl salts of weak acids have a basic reaction in aqueous solution as a result of hydrolysis Tl forms polysulfldes (e.g. TI2S3) and polyiodides, etc. In other respects Tl resembles the more highly polarizing ion Ag+, e.g. in the colour and insolubility of its chromate, sulfide, arsenate and halides (except F), though it does not form ammine complexes in aqueous solution and its azide is not explosive. 

This compound is deposited on the metal surface unless the solution is sufficiently acid to dissolve it as soon as it is formed. The him also usually contains the oxide of the metal being treated, together with alkali metal (when this is present in the treatment solution) perhaps in the form of a complex basic double chromate analogous to zinc yellow. 

O-Donor Ligands. The d.t.a. characteristics of chromates and isopolychromates have been reviewed and the heats of formation of several alkali-metal and... 

LiAlH4 as this avoids protonation of the enolate and the production of any over-reduction products. Cholest-4-en-3-one may be reduced to cholestanone (5a 5/8,1 19) with alkali-metal carbonyl chromates. The studies on intramolecular hydride shifts on hydroxy-ketones and -aldehydes have been extended. " The hydride shifts were examined in a number of y- and 5-hydroxy-carbonyI compounds by heating the substrates with alkaline alumina containing D2O. Exchange of protons on the carbon a to both oxygen functions signals the intramolecular hydride shift typically, the hemiacetals (95) and (96) each incorporate up to six deuterium atoms. The general conclusion, in common with literature precedent, is that, whereas 1,5-shifts are common, 1,4-shifts are rare. 

The Cr04 and Cr20y anions give rise to numerous salts. Chromates of the alkali metal cations, NH4+, Mg+, Ca+, and Mn+ are soluble most others are insoluble. Almost all dichromates are soluble, that of Ag" " being insoluble. 

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

Electrochemical Process. Several patents claim that ethylene oxide is produced in good yields in addition to faradic quantities of substantially pure hydrogen when water and ethylene react in an electrochemical cell to form ethylene oxide and hydrogen (206—208). The only raw materials that are utilized in the ethylene oxide formation are ethylene, water, and electrical eneigy. The electrolyte is regenerated in situ, ie, within the electrolytic cell. The addition of oxygen to the ethylene is activated by a catalyst such as elemental silver or its compounds at the anode or its vicinity (206). The common electrolytes used are water-soluble alkali metal phosphates, borates, sulfates, or chromates at ca 22—25°C (207). The process can be either batch or continuous (see Electrochemical processing). 

H. M. Dawson and J. McCrae, D. P. Konowaloff, and W. Gaus also used soln. of various salts of the alkali metals, and of potassium, sodium, cupric, or barium hydroxide in place of water and also copper sulphate, copper chloride, zinc sulphate, and cadmium iodide while M. 8. Sherrill and D. E. Russ examined the effect of ammonium chromate. W. Herz and A. Kurzer examined the distribution of ammonia between water and a mixture of amyl alcohol and chloroform. Observations on the distribution of ammonia between water and chloroform were made by T. S. Moore and T. F. Winmill, G. A. Abbott and W. C. Bray, and J. M. Bell. J. H. Hildebrand gave for the molar fraction N X104 of ammonia at 1 atm. press., and 25°, dissolved by ethyl alcohol, 2300 methyl alcohol, 2730 and water, 3300. 

All compounds containing chromates, CrC 2- Are insoluble Except those containing alkali metals or nh4+... 

In order to limit the reduction of perborate at the cathode alkali metal chromate or bichromate (to achieve a concentration of about 0.3 g. Cr03 per litre) is added to the electrolyte. Apart from this, a too low current density, below 10 A/sq.dm, should not be used at the cathode. 

Solubility The chromates of the alkali metals and of calcium and magnesium are soluble in water strontium chromate is sparingly soluble. Most other metallic chromates are insoluble in water. Sodium, potassium, and ammonium dichromates are soluble in water. 

Chromates are generally insoluble or sparingly soluble exceptions are those of the alkali metals and Ca, Sr, Mg, Mn, Zn, Fe, and Cu. 

Defined as those containing only the simple MO ions, they can be obtained from solutions of M03 in aqueous alkali. The MO ions persist as such in basic solution. Although both molybdates and tungstates can be reduced in solution (see later), they lack the powerful oxidizing property so characteristic of chromates(VI). The normal tungstates and molybdates of many other metals can be prepared by meta-thetical reactions. The alkali metal, ammonium, magnesium, and thallous salts are soluble in water, whereas those of other metals are nearly all insoluble. 

On the other hand, iron remains perfectly bright and free from all traces of corrosion when immersed in solutions of the chromates or bichromates of the alkali metals, unless, indeed, the solutions are excessively dilute. This is generally attributed to the formation of a thin film of oxide on the surface of the metal which shields the under-lying portions from attack, but this is not the only explanation, as has been seen (p. 71). 

Chromates of alkali metal, alkaline earth metal and ammonium 100)... 

Cationic polymerization of epoxides by irradiation of charge-transfer complexes has been mentioned in the literature Fluorinated alkanesulfonic acid salts chromates and dichromates of alkali metals, alkaline earth metals and ammonium phototropic o-nitrobenzyl esters iodocyclohexene unsaturated nitrosamines and carbamates have been reported to act as cationic photoinitiators. 

Reduction of Cr04 (chromates(VI)) yields Cr04 ions (chromates(V)), which can be isolated in the form of their alkali metal and alkaline-earth metal salts, for example, Na3Cr04 and Ba3(Cr04)2. The black or blue paramagnetic salts contain isolated Cr04 tetrahedra and are hygroscopic upon dissolution in water they disproportionate to and Cr. ... 

Mg is insol in cold w si sd in hot w, with which it reacts sol in mineral acids, cone HF and Amm salts insol in chromates alkali In 1808, Sir Humphry Davy reported the production of Mg in the form of an amalgam by electrolytic reduction of its oxide using a Hg cathode. In 1828, the Fr scientist A. Bussy fused Mg chloride with metallic K and became the first to produce free metallic Mg. Michael Faraday, in 1833, was the first to produce free metallic Mg by electrolysis, using Mg chloride. For many years, however, the metal remained a laboratory curiosity. In 1886, manuf of Mg was undertaken on a production scale in Ger, using electrolysis of fused Mg chloride. Until 1915, Ger remained the sole producer of Mg. However, when a scarcity of Mg arose in the USA as a result of the Brit blockade of Ger in 1915, and the price of Mg soared from 1.65 to 5.00 per lb, three producers initiated operations and thus started a Mg industry in the USA. Subsequently, additional companies attempted production of Mg, but by 1920 only two producers remained — The Dow Chemical Co (one of the original three producers) and. the American Magnesium Corp. In 1927, the latter ceased production, and Dow continued to be the sole do- mestic producer until 1941. The source of Mg chloride was brine pumped from deep wells. In 1941, Dow put a plant into operation at Freeport, Texas, obtaining Mg chloride from sea-... 

Chromates are usually yellow or red in colour, and, except those of ammonium, the alkali metals, calcium, strontium, and magnesium, are practically insoluble in w ater. They are obtained by oxidation of chromites, by fusion of chromium sesquioxide with the appropriate base in presence of air or of an oxidising agent by oxidation of chromium salts in solution or by double decomposition. Normal, di-, and tri-clrromates, etc., are derived from one and the same acid oxide KaCrOj behaves like an alkali torvards CrOg, since it is quantitatively converted into dichromate. A large number of complex double chromates are known. 

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