Chromium acetate sulphate

With each of these four groups the procedure is as described later. In the first place, however, the colouring matter is investigated with reference to its tintorial properties by means of dyeing tests on non-mordanted cotton or wool, on wool mordanted with aluminium sulphate and cream of tartar, on wool mordanted with chromium fluoride and cream of tartar, on cotton mordanted with tannin and then with tartar emetic, on cotton mordanted with aluminium acetate and on cotton mordanted with chromium acetate. 

Medium acid baths, pH 4-5 At this acidity a dichromate solution plus sulphate ion as activator is sufficient to deposit chromate films in 30 min or so at room temperature or in a few minutes at boiling point. Unfortunately, a solution of alkali dichromate and alkali sulphate is quite unbuffered, and other substances must be added to give the bath a useful life over the working pH range. Acetates have been used successfully, but salts of aluminium, chromium, manganese and zinc have been more commonly employed. The pH of the solution rises slowly during use until basic chromates or sulphates begin to precipitate. The solution can then be rejuvenated by the addition of chromic or sulphuric acid or acid salts. 

Cr-ZSM-5 catalysts prepared by solid-state reaction from different chromium precursors (acetate, chloride, nitrate, sulphate and ammonium dichromate) were studied in the selective ammoxidation of ethylene to acetonitrile. Cr-ZSM-5 catalysts were characterized by chemical analysis, X-ray powder diffraction, FTIR (1500-400 cm 1), N2 physisorption (BET), 27A1 MAS NMR, UV-Visible spectroscopy, NH3-TPD and H2-TPR. For all samples, UV-Visible spectroscopy and H2-TPR results confirmed that both Cr(VI) ions and Cr(III) oxide coexist. TPD of ammonia showed that from the chromium incorporation, it results strong Lewis acid sites formation at the detriment of the initial Bronsted acid sites. The catalyst issued from chromium chloride showed higher activity and selectivity toward acetonitrile. This activity can be assigned to the nature of chromium species formed using this precursor. In general, C r6+ species seem to play a key role in the ammoxidation reaction but Cr203 oxide enhances the deep oxidation. 

The process can be used to immobilize heavy metals such as Cd, Zn, Cu, Pb, Ni and Co. Cr(VI) can be reduced by some metal-reducing bacteria to the less toxic and less soluble form Cr(III). Arsenate [As(V)] can be reduced to the more mobile arsenite [As(III)] which precipitates as AS2S3, and is insoluble at low pH. Several laboratory-scale tests (batch and column) are currently available to study the feasibility of this process. However, only a few field tests have been performed to date. Two such tests have been conducted in Belgium, one at a non-ferrous industrial site, where the groundwater was contaminated with Cd, Zn, Ni and Co, and the other which was treated by injection of molasses in order to reduce chromium (VI) to chromium (III). A third demonstration in The Netherlands has been performed at a metal surface treatment site contaminated by Zn. The outcomes of a batch test of a groundwater heavily contaminated by Zn, Cd, Co and Ni are presented in Table 5. The initial sulphate concentration was 506mg/l. With the addition of acetate, a nearly... 

The limited applications of this technique, to date include fluoride, chloride, bromide, nitrite, nitrate, sulphate, sulphide, phosphate, amino acetate, chlorodicarboxylic acids, volatile organic acids and chromium(VI). 

Silver chromate is almost insoluble in water, glacial acetic acid, and in solutions of potassium chromate, but soluble in those of ammonia, caustic alkalies, nitrates, and in dilute acetic acid. A concentrated solution of ammonium nitrate is a good crystallising medium for silver chromate. With chlorine, above 200° C., silver chloride, chromium trioxide, and oxygen are produced. The solution in ammonia contains the compound Ag2Cr04.4NH3, which forms crystals isomorphous with the corresponding ammoniacal sulphate. ... 

Chromous Sulphate, CrSOi.VHgO, is produced by dissohdng chromous acetate in dilute sulphuric acid, or by interaction of chromium and sulphuric acid. It forms blue crystals, isomorphous with those of FeSO. THjO, and is soluble in water, though not in alcohol. It is readily oxidised by the oxygen of the air. Moissan describes a hydrate, CrSO. HgO, as a white powder, which with water regenerates the hepta-hydrate. ... 

Chromium may also be completely precipitated as the phosphate, CrPOj, by the addition of an alkali phosphate in presence of sodium acetate. The method gives satisfactory results with the green and violet chlorides, sulphates, and acetates, but not with oxalates (see p. 87). 

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-... 

Involutin (145) is responsible for the intense brown stain produced when the fruit body of Paxillus involutus is bruised. It formed a penta-acetate which, on oxidation with chromium trioxide or potassium permanganate solution gave a mixture of 3,4-diacetoxybenzoic acid and 4-acetoxybenzoic acid. With dimethyl sulphate and sodium hydroxide the trimethyl ether (151) resulted 201, 202). These observations, coupled with spectroscopic comparison with model compounds, established the nature of the cyclopentanoid nucleus and the level of hydrox-... 

In most of the investigations mentioned so far in this section involving solvent mixtures it is likely that the primary solvation shell does not vary with solvent composition. However, there are occasions when variation of reactivity with solvent mixture composition is attributed to changes in primary solvation shell composition, as in the case of reaction of Ni + with ammonia in aqueous methanol. In the reaction of Be + with sulphate in aqueous DMSO, there is strong n.m.r. evidence for variation in primary solvation shell composition. In the reaction of Co with tetraphenylporphine in acetic acid-water the kinetics also reflect the presence of varying amounts of mixed solvates. By way of contrast, in reactions of copper(ii) with polythiaethers in methanol-water mixtures only Cuaq + reacts mixed solvates are claimed to be of negligible reactivity. In the reaction of chromium(iii) with edta in methanol- and ethanol-water mixtures, variation in pK for the Cr + has an effect on the formation rates, but the individual rate constants for the reactions of Cr + and of CrOH + with the ligand seem to be practically independent of solvent composition. ... 

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