Chrome Fast Pure Blue

Test with Chrome Fast Pure Blue... 

When a mineral acid solution of an aluminum salt is treated with a water solution of the oxytriphenylmethane dye known as Chrome Fast Pure Blue B... 

Corresponding to this viewpoint, all hydroxytriphenylmethane dyes containing the group A react in the same fashion as Chrome Fast Pure Blue B when they come into contact with aluminum salts. To these color reactions the general formulation can be given ... 

The chelate compounds, produced as shown in (2), are not decomposed at once by even (1 1) sulfuric acid and therefore a sensitive test for aluminum has been developed on this basis. (Tervalent chromium salts exhibit an analogous behavior.) The color reactions are selective if the test solution is treated with a shght excess of magnesium carbonate before the reagent is introduced. It is essential that sulfuric acid be used for the acidification if hydrochloric acid is employed the zirconimn compounds formed at the same time remain unchanged. The sulfuric acid probably decomposes the colored zirconium compounds through formation of complex zirconium sulfuric acids. Chrome Fast Pure Blue B is the best reagent because its dye acid can be completely extracted by ether, which is not true of some of the related dyes. 

Procedure. The test is conducted in a micro test tube. Pulverized magnesium carbonate is added cautiously to one drop of the acidic test solution until the evolution of carbon dioxide stops. The excess of MgCOg should be as slight as possible. One drop of a 5 % water solution of Chrome Fast Pure Blue B is added and the solution then acidified with a drop of 1 1 sulfuric acid. If the quantity of aluminum is small, the excess dye acid will precipitate, whereas the dye may be completely consumed if large amounts of aluminum are present. The system is now shaken with 10-16 drops of ether. Any excess dye enters the ether and the lower water layer becomes magenta or pink. 

The almost specific test for aluminum with Chrome Fast Pure Blue B (see page 100) can be used for the rapid detection of traces of this element in water. Only 25-50 ml is required. After adding one drop of a 1 % solution of iron i chloride or sulfate, ammonium hydroxide is added and the suspension is centrifuged in portions and the precipitate thus gathered in a conical centrifuge tube. The hydrous ferric oxide acts as collector for the hydrous alumina. The precipitate on the bottom of the tube is dissolved in a drop or two of a mixture of equal volumes of 2 iV hydrochloric acid and 80 % thioglycolic acid. One drop of a 5 % water solution of the dye is added and the mixture then made basic with ammonium hydroxide. Finally, the system is acidified with 1 1 hydrochloric acid and shaken with ether. The ether layer is pink if the response is positive. 

The color reaction with the hydroxytriphenylmethane dye Chrome Fast Pure Blue B (see page 100) can be used for the detection of alumina in samples that have been decomposed by fusion with alkali bisulfate or persulfate. A much faster method is to allow an ether solution of this dye to act on the pulverized sample a red-violet tinting occurs almost at once. Beryllium oxide is made deep blue. These colored products, which are probably adsorption complexes, differ characteristically in that the alumina adsorbate is resistant to dilute acids. 

Carboxy-5-methyl-4-oxo-2,5-cyclohexadien-l-ylidene) (2,6-dichloropheny[)methy[ -2 hydroxy-3-methylbenzoic acid, 9CI. Pontachrome azure blue B. Chrome fast pure blue B. C.I. 43830. C.I. Mordant blue I. Eriochrome azurol B. Acid chrome pure blue [15012-28-9]... 

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