Barium chromate, precipitation

When yellow aqueous potassium chromate is added to a colorless barium nitrate solution, yellow barium chromate precipitates. 

The pH can also be controlled by evaporation of ammonia. For example, barium chromate can be precipitated in the presence of strontium and lead by first complexing the metal ions at a pH of 10.4, followed by evaporation of ammonia. The pH decreases slowly, and barium chromate precipitates since the barium ion is no longer complexed at the lower pH. ... 

A solution of barium chromate (BaCr04) is prepared by dissolving 6.3 X 10 g of this yellow solid in 1.00 L of hot water. Will solid barium chromate precipitate upon cooling to 25°C, according to the solubility product expression Explain. 

To be more precise, the concentrations of the starting substances decrease, i.e., barium chromate precipitates until equilibrium is established. 

The classical analytical method of deterruination of barium ion is gravimetric, by precipitating and weighing insoluble barium sulfate. Barium chromate, which is more insoluble than strontium chromate in a slightly acidic solution, gives a fairly good separation of the two elements. 

Other reagents which may be applied to the volumetric determination of sulphuric acid and sulphates are barium chromate and benzidine. In the case of the former, the solution of sulphate is precipitated by a solution of barium chromate in hydrochloric acid on subsequent neutralisation of the filtrate, a quantity of chromic acid, equivalent to the barium sulphate which has been precipitated, remains in solution and may be estimated iodometrically.6 Benzidine, on the other hand, is an organic base which forms a very sparingly soluble sulphate the solution of mineral sulphate is treated with a solution of benzidine hydrochloride and the precipitated benzidine sulphate removed by filtration when subsequently suspended in pure water the benzidine sulphate undergoes hydrolysis to a sufficient extent to permit titration of the sulphuric acid with standard alkali.7 Lead nitrate may also be... 

Barium chromate. [CAS 10294-40-3]. BaCrO yellow precipitate, K,sp = 1.17 < 10-10, formed by reaction of barium salt solution and potassium chromate solution,... 

Barium chloride Pale yellow precipitate of barium chromate soluble in dilute mineral acids insoluble in water and in acetic acid... 

Why is it necessary to use scavenge techniques for the removal of barium (by barium chromate) and plutonium (by ferric hydroxide precipitation) ... 

What is the precipitate From experience, you know that NaCI is water soluble. So, by process of elimination, the precipitate must be barium chromate, BaCr04(s). 

Potassium chromate solution a yellow precipitate of barium chromate, practically insoluble in water (3-2 mg t l, Ks = 16 x 10"10) ... 

Sodium rhodizonate reagent reddish-brown precipitate of strontium rhodi-zonate in neutral solution. The test is applied to the elements of Group IV. Barium reacts similarly and a method for the detection of barium in the presence of strontium has already been described (Section III.31, reaction 7). To detect strontium in the presence of barium, the latter is converted into the insoluble barium chromate. Barium chromate does not react with sodium rhodizonate, but the more soluble strontium chromate reacts normally. 

Barium perferrate,2 BaFe04.H20, is obtained as a purple precipitate on addition of barium chloride to a solution of the calcium salt 3 or of barium chromate to a solution of sodium perferrate.4... 

Barium chromate readily dissolves in hydrochloric and nitric acids, forming the dichromate concentrated sulphuric acid decomposes it, forming barium sulphate and chromic acid it also dissolves in molten sodium nitrate. The simultaneous precipitation of barium chromate and barium carbonate, and of barium chromate and barium sulphate, has been studied. ... 

Double salts of barium chromate, for example, BaK2(Cr04)2, Ba(NH4)2(Cr04)2, are obtained as light yellow precipitates by adding... 

A chromate may be detected in presence of a dichromate in several ways. If the precipitation of barium chromate by excess of barium chloride leaves an acid solution, a diehromate is indicated. Excess of methylene blue gives a precipitate with dichromates, and if a chromate is present a further precipitate is obtained on adding dilute sulphuric acid to the filtrate. A concentrated solution of manganese sulphate added to a boihng solution gives a blackish-brown precipitate if a chromate is present while by mixing the hot solution with an equal volume of a boiling solution of sodium thiosulphate, a distinct turbidity, or even a brown precipitate of chromium sesquioxide, is produced by a dichromate. 

If the chromium is in solution as a chromate or dichromate, as is the case after fusion as described above, it may either be reduced to the trivalent condition and precipitated as hydroxide, or directly precipitated as an insoluble chromate. In the absence of sulphates, barium chromate is precipitated by the addition of barium acetate at the boiling-point to a solution made faintly acid -with acetic acid and containing a little alcohol. After ignition the precipitate is w eighed as barium chromate. If chlorides and sulphates are present only in small amount, the chromate may be thrown down by mercurous nitrate, the mercurous chromate then being converted by ignition to the sesqui-... 

An outline of the method used for determination of radiostrontium in various materials by nitrate precipitation is as follows. The ashed material is dissolved in nitric acid in the presence of strontium and barium carriers. The nitric acid concentration is then increased to precipitate all the strontium and barium (and part of the calcium) as nitrates. After further nitric acid separations, barium chromate and iron hydroxide scavenges are carried out. The subsequent treatment depends somewhat on the circumstances but the following is normal practice. 

J. Thomsen, and J. Krutwig similarly treated silver chromate with hydrochloric acid. A. Mailfert found that chromium trioxide is formed when soln. of chromic salts or chromic oxide are treated with ozone. M. Prud homme and F. Binder observed that if barium chloride is added to a soln. of barium dichromate, normal barium chromate is precipitated, and potassium chloride and chromic acid remain in soln. In preparing chromic acid, V. V. Polyansky first obtained calcium chromate by addition of calcium hydroxide paste, followed by calcium chloride soln., to... 

When an aq. soln. of a barium salt, or baryta-water is treated with alkah mono- or di-chromate, a pale yellow precipitate of barium Chromate, BaCr04, is deposited. J. D. Smith said that the precipitation with a barium salt is as delicate a test for chromate as it is for sulphates. F. T. Frerichs, and H. Kammerer obtained a complete precipitation in the presence of acetic acid or sodium acetate. 

Ruff and E. Asoher studied the joint precipitation of lead and barium chromates barium and strontium chromates and barium sulphate and chromate and... 

The pale lemon-yellow barium chromate was found by H. Moser to become dark yellow when heated. L. Bourgeois said that the rhombic prisms are isomorphous with barium sulphate and A. de Schulten gave for the axial ratios of the rhombic plates a 6 c=0-8038 1 1-2149. F. Rinne studied the crystals of barium chromate and M. Copisarow observed tree-like, dendritic forms are produced when the precipitate is slowly formed. The sp. gr. observed by H. G. F. Schrdder is 4-296—4-304 C. H. D. Bodecker, 3-90 at 11° E. Schweizer, 4-5044 A. Schafarik,... 

For the equilibrium between barium chromate and dichromate, vide supra, chromic acid. I. Meschtschersky found that a litre of water dissolved 4-3 mgrms. at 100°. C. R. Fresenius said that at 0°, a litre of water dissolves 1-19 mgrms. The salt is less soluble after it has been ignited. E. Schweizer said that in that state a litre of water dissolves 0-62 mgrm. L. M. Henderson and F. C. Kracek pointed out that the solubilities of the alkaline earth chromates decrease as the at. wt. of the alkaline earth metal. Thus, at 15°, the solubilities of the anhydrous calcium, strontium and barium chromates are of the order 25,1-2, and 0-0033 grms. per litre respectively. The solubility of ladiom chromate seems to follow the rifle, and a separation of radium and barium can be effected by fractional precipitation as chromates. The partition factor for acidic soln. is about 15-5. 

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