Mercury vanadates

Minor uses of vanadium chemicals are preparation of vanadium metal from refined pentoxide or vanadium tetrachloride Hquid-phase organic oxidation reactions, eg, production of aniline black dyes for textile use and printing inks color modifiers in mercury-vapor lamps vanadyl fatty acids as driers in paints and varnish and ammonium or sodium vanadates as corrosion inhibitors in flue-gas scmbbers. 

Molybdenum(VI), vanadium(V), mercury, and iron interfere permanganates, if present, may be removed by boiling with a little ethanol. If the ratio of vanadium to chromium does not exceed 10 1, nearly correct results may be obtained by allowing the solution to stand for 10-15 minutes after the addition of the reagent, since the vanadium-diphenylcarbazide colour fades fairly rapidly. Vanadate can be separated from chromate by adding oxine to the solution and extracting at a pH of about 4 with chloroform chromate remains in the aqueous solution. Vanadium as well as iron can be precipitated in acid solution with cupferron and thus separated from chromium (III). 

Chemically pure vanadium pentoxide is alternatively prepared by precipitating insoluble mercurous vanadate, HgV03, from a neutral solution of a vanadate, and distilling off the mercury, or by ignition of vanadium salts of volatile acids, for example, vanadium oxytrichloride, VOCl3. The oxide also results from the oxidation of any of the lower oxides, or by the electrolysis of a solution of sodium vanadate or copper vanadate, using a divided cell the last method yields a product of 98 per cent, purity.2... 

Occluded hydrogen is more reactive chemically than the normal gas. Hydrogenated palladium precipitates mercury and mercurous chloride from an aqueous solution of the dichloride, without any evolution of hydrogen. It reduces ferric salts to ferrous potassium ferricyanide to ferrocyanide chlorine water to hydrochloric add iodine water to hydriodic acid 2 chromates to chromic salts ceric to cerous salts whilst cupric, stannic, arsenic, manganic, vanadic, and molybdic compounds are also partially reduced.3... 

Cadmium pigments Mercury cadmium pigments Lead chromate yellows Lead molybdate oranges Iron blues Chrome greens Bismuth vanadate... 

Manganese ions interfere (oxidized to permanganate) as do also mercury(II) salts, molybdates, and vanadates, which give blue to violet compounds with the reagent in acid solution. The influence of molybdates can be eliminated by the addition of saturated oxalic acid solution thereby forming the complex H2[Mo03(C204)]. 

Mercury(I) nitrate solution white precipitate of mercury(I) vanadate from neutral solutions. 

Cr(II) may be used to carry out all the reactions of Ti(III), but usually under milder conditions. Applications of Cr(II) as a reductant have been reviewed. The applications include Sn(IV) chloride in the presence of catalysts such as Sb(V) or Bi(III), Sb(V) in 20% HCl at elevated temperatures, Cu(II), silver, gold, mercury, bismuth, iron, cobalt, molybdenum, tungsten, uranium, dichromate, vanadate, titanium, thallium, hydrogen peroxide, oxygen in water and gases, as well as organic compounds such as azo, nitro, and nitroso compounds and quinones. Excess Cr(II) in sulfuric acid solution reduces nitrate to ammonium ion. The reduction is catalyzed by Ti(IV), which is rapidly reduced to Ti(III). 

The carbonates, sulphates, and borates are decomposed. The sulphides of the alkalies and alkaline earths are decomposed while the sulphides of arsenic, antimony, molybdenum, zinc, cadmium, tin, iron, lead, copper, mercury, and palladium are not attacked. Cobalt sulphate is not attacked, while the sulphates of the alkalies and alkaline earths are attacked and dissolved. Alkali tungstates, ammonium arsenite and arsenate, copper arsenite, ammonium magnesium arsenate, ammonium molybdate and vanadate, potassium cyanide and ferrocyanide are decomposed. Paraffin is not attacked shellac, gum arabic, gum tragacanth, copal, etc., are decomposed. Celluloid is slowly attacked. Silk paper, gun cotton, gelatin, parchment are dissolved. M. Meslans 22 has studied the esterification of alcohol by hydrofluoric acid. 

If the pH value in the PAR reagent is lowered to 8.8 by adding a phosphate buffer, gallium(III), vanadium(IV)/(V), and mercury (II) can be detected and may be separated from the other heavy metals with PDCA as the eluent [151]. Fig. 3-157 shows the separation of vanadium(V) that was applied as ammonium(meta)vanadate, NH4V03. Under these conditions, vanadium(IV) elutes after about 17 minutes the two most important oxidation states of vanadium being easily distinguished. Gallium(III), of particular importance for the semiconductor industry, elutes near the void volume. 

Cadmimn, copper, mercury, silver, and tin form white precipitates with thiourea when present in high concentrations. Only antimony(III) (and vanadate) gives a weak yellow color with thiourea. Hg, SeOj and SeO " are reduced and interfere by forming colored complexes and precipitates. ... 

In the high-pressure mercury lamps for street lighting, yttrium vanadate doped with europium is deposited on the glass. This makes the light brilliant white and more natural. 

Mercury salts, molybdates, and also vanadates give blue to violet compounds with diphenylcarbazide in acid solution, and therefore interfere with the chromium test. The interference can be prevented by the addition of suitable compounds which lower the ionic concentration of the interfering elements below that required for the diphenylcarbazide reaction. For mercury, it is sufficient to add an excess of hydrochloric acid or alkali chloride the usual low dissociation of mercury chloride is thus even further reduced. (The formation of the complex [HgClJ ions also helps to lower the ionic concentration of mercury.) When chromium is to be detected in the presence of mercury, hydrochloric acid is used to acidify the alkaline chromate solution. In this way, 0.25 y chromium is easily detected by a spot reaction in the presence of 2.5 mg mercury (1 10,000). 

The physical properties of the rare earth vanadates have been widely investigated. They show interesting magnetic as well as optical properties. Their most important technical significance is in the use of Eu YVO4 red phosphor in high pressure mercury lamps (Palilla et al., 1965 Luscher and Datta, 1970). 

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