Vanadium ammonium sulphate

The estimation of a vanadate solution by direct titration with ferrous sulphate or ferrous ammonium sulphate solution has been worked out, and is found to be specially applicable to the analysis of vanadium alloys. The vanadate is again reduced to tire tetravalent state by the ferrous salt, the end point being obtained by the use of potassium ferricyanide as internal indicator alternatively, a known excess of the ferrous salt solution is added to the vanadate, the amount unused... 

In method (a) 2M to 3M ammonium sulphate solutions are used to elute the uranium. The vanadium can then be eluted by a number of reagents, of which a saturated aqueous solution of sulphur dioxide is probably the most satisfactory. An example of method (b) is to use saturated sulphur dioxide solution first, for vanadium elution, followed by 0-9M sodium chloride solution which is 0-1N in hydrochloric acid, for elution of the uranium. In method (c) absorption is allowed to proceed beyond the point of uranium breakthrough and is stopped when breakthrough of vanadium occurs, by which time all the uranium on the resin has been replaced by vanadium. The effluent thus contains a higher concentration of uranium than the feed solution when this replacement is taking place. The concentrated uranium in this effluent is absorbed readily upon a second column. Aqueous sulphur dioxide can be used for elution of the vanadium loaded column, and acidified chloride solution for elution of the one loaded with uranium. 

With the exception of iron(II) and uranium(IV), the reduced solutions are extremely unstable and readily re-oxidise upon exposure to air. They are best stabilised in a five-fold excess of a solution of 150g of ammonium iron(III) sulphate and 150 mL of concentrated sulphuric acid per litre [approximately 0.3M with respect to iron] contained in the filter flask. The iron(II) formed is then titrated with a standard solution of a suitable oxidising agent. Titanium and chromium are completely oxidised and produce an equivalent amount of iron(II) sulphate molybdenum is re-oxidised to the Mo(V) (red) stage, which is fairly stable in air, and complete oxidation is effected by the permanganate, but the net result is the same, viz. Mo(III)- Mo(VI) vanadium is re-oxidised to the V(IV), condition, which is stable in air, and the final oxidation is completed by slow titration with potassium permanganate solution or with cerium(IV) sulphate solution. 

Normal carbonates of vanadium are unknown. An unstable ammonium vanadyl carbonate, of composition 3(NH4)2C0S.7V02.5C02. 16H20, has been obtained in small, violet crystals by the addition of ammonium carbonate to a neutral solution of vanadyl sulphate.4... 

Electrometric Methods have been applied for the estimation of vanadium alone and alloyed with other metals, e.g. iron, chromium, uranium. The reduced solution is either gradually oxidised by means of a suitable oxidising agent (potassium permanganate, ammonium persulphate, nitric acid), or the vanadate solution is gradually reduced with ferrous sulphate solution the changes in the E.M.F. of a suitable cell indicate the end point.8... 

Colorimetric Methods are used only for the estimation of very small percentages of vanadium, e.g. in vanadium steels and alloys. The most important depend on the intensity of the reddish-brown colour produced by the action of hydrogen peroxide on an acid vanadate solution.3 If chromium is present, an equal amount must be introduced into the standard vanadium solution under the same conditions of temperature, acid concentration, etc. Phosphoric acid is added to destroy any yellow colour due to ferric iron, and either hydrofluoric acid or ammonium fluoride to destroy any colour produced by titanium.4 A colorimetric method for the simultaneous estimation of small quantities of titanium and vanadium has also been worked out.5 Other colorimetric processes are based on (a) the formation of a yellow to black coloration, due to aniline black, in the presence of aniline hydrochloride and potassium chlorate or other oxidising agent,6 and (b) the orange coloration finally produced when an acid solution of a vanadate is brought into contact with strychnine sulphate.7... 

Carnotite may be fused Avith potassium hydrogen sulphate and the residue extracted with Avater. From the solution the double sulphates of potassium AAuth uranium and vanadium may be obtained by crystallisation. These are reduced by means of zinc and sulphuric acid, and the vanadium precipitated from the solution by means of ammonia and ammonium carbonate. Ammonium diuranate separates from the filtrate on boiling. ... 

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