Ammonium vanadate metavanadate

Cobalt Metavanadate, Co(V03)2.Sli20, separates out on boiling a solution of ammonium vanadate with excess of cobalt nitrate which has been feebly acidified with nitric add.9 It is easily soluble in water. 

Aminonium Polyvanadates.—The compound (NH4)20.3V205 appears to be the most stable of the arid ammonium vanadates. It is formed by addition of a 10 per cent, solution of acetic acid to a solution of ammonium metavanadate, or by boiling an aqueous solution of any other ammonium polyvanadate. It forms thin, transparent, yellow, octagonal plates, or golden, microscopic, rhombic plates which become temporarily vermilion on being heated, and which are only slightly soluble in water. It has also been obtained combined with two, five, or six molecules of water, according to the temperature of crystallisation or extent of dehydration.2... 

Ammonium Vanadate Solution (0.25%) Dissolve 2.5 g of ammonium metavanadate, NH4VO3, in 600 mL of boiling water, cool to 60° to 70°, and add 20 mL of nitric acid. Cool to room temperature, dilute to 1000 mL with water, and mix. 

For direct precipitation of vanadium from the salt-roast leach Hquor, acidulation to ca pH 1 without the addition of ammonia salts yields an impure vanadic acid when ammonium salts are added, ammonium polyvanadate precipitates. The impure vanadic acid ordinarily is redissolved in sodium carbonate solution, and ammonium metavanadate precipitates upon addition of ammonium salts. Fusion of the directly precipitated ammonium salts can yield high purity V20 for the chemical industry. Amine solvent extraction is sometimes used to recover 1—3 g/L of residual V20 from the directly precipitated tail Hquors. 

Vanadium usually is recovered from its ores by one of two processes, (1) leaching raw mineral with hot dilute sulfuric acid, and (2) roasting ore with common salt to convert vanadium into water soluble sodium vanadates. In the sulfuric acid leaching process, vanadium is extracted from acid leach liquors by solvent extraction with an aliphatic amine or an alkyl phosphoric acid in kerosene. The organic solvent extract then is treated with an aqueous solution of ammonia in the presence of ammonium chloride to convert vanadium into ammonium metavanadate. Alternatively, the organic extract is treated with dilute sulfuric acid or an aqueous solution of soda ash under controlled conditions of pH. Vanadium is precipitated from this solution as a red cake of sodium polyvanadate. 

Colloidal Vanadium Pentoxide.11—When a soluble vanadate is treated with mineral acids, a red, curdy form of vanadium pentoxide is precipitated, which, on being shaken with water, appears to dissolve to a red liquid. This reaction gives rise to the following usual method for making a colloidal solution Ammonium metavanadate, NH4V03, is made into a paste with 10 per cent, hydrochloric acid of 10 per cent, concentration, and the resulting gel of vanadium pentoxide is washed repeatedly on the filter with distilled water until it assumes the colloidal form, i.e. until it is peptised, and in consequence passes through the... 

Lead Metavanadate, Pb(VOg)2.—Acid solutions of vanadates on being treated with lead salts give rise to yellow basic vanadates the composition of which varies with the conditions. The precipitation of normal lead vanadate is, therefore, difficult. It has been accomplished by the addition of lead acetate to ammonium metavanadate solution in the presence of acetic acid.2 The lead precipitates contain all the vanadic acid originally present in solution, and precipitation of vanadates with lead salts has, therefore, been employed for the quantitative estimation of vanadium.3 The mineral deschenite consists chiefly of lead metavanadate a portion of the lead is, however, frequently replaced by zinc.4... 

Thallium Poly vanadate.—By treating ammonium metavanadate with... 

The gravimetric estimation of vanadium in alkaline vanadate solutions has also been effected by precipitating as ammonium metavanadate in the presence of ammonium chloride.6 Precipitation is incomplete, however, unless the solution is quite saturated with ammonium chloride 7 the addition of alcohol is recommended.8 Other gravimetric processes which have been investigated include the precipitation of barium pyrovanadate,9 precipitation of silver metavanadate,10 precipitation of manganese pyrovanadate,11 and the use of cupferron.12... 

The solution chemistry of the rare earth vanadates has received considerable attention [359,360]. It has been found that when ammonium metavanadate solution is added to rare earth nitrate solutions, an increase in acidity results with the formation of the orthovanadates (eq. 35). However, when the solutions are mixed in the opposite order the pH of the medium remains unchanged and precipitates of metavanadates the (eq. 36) are produced. 

Vanadate solutions are usually prepared from sodium orthovanadate, Na3V04, or sodium metavanadate, NaV03, or from the corresponding ammonium salts. These give the same vanadate species in solution after equilibration. In vitro assays of the effect of vanadate reported in the literature have used a wide range of concentrations, ca 10 mM to 1 nM. It is instructive to examine the species of vanadate which are expected to be present under conditions of equilibrium at these concentrations of vanadium. 

SYNS AMMONIUM METAVANADATE pOT) RCRA WASTE NUMBER PI 19 VANADIC ACID, AMMONIUM SALT... 

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