Chromic hydrate

Formula Cr(0H)3 3H20 MW 157.06 occurs only as hydrates Synonyms chromic hydroxide chromic oxide hydrous chromic oxide gel chromium hydrate chromic hydrate. 

Ionisation Isomerism.—This is shown in the chromic hydrates, ehloro-pentaquo-chromic sulphate, [Cr(H20)5Cl]S04, and sulphato-pentaquo-chromic chloride, [Cr(H20)BS04]Cl.(l... 

Chromic acid strontium salt Chromic acid strontium salt (1 1). See Strontium chromate Chromic acid, zinc salt. See Zinc chromate Chromic anhydride. See Chromium trioxide Chromic chloride. See Chromium chloride (ic) Chromic chloride stearate. See Stearatochromium chloride complex Chromic fluoride. See Chromium fluoride (ic) Chromic hydrate Chromic hydroxide Chromic (III) hydroxide. See Chromium hydroxide (ic) Chromic nitrate. See Chromium nitrate Chromic oxide. See Chromium oxide (ic) Chromic oxide hydrated. See Chromium hydroxide green... 

Synonyms Chromic acid sol n. Chromic hydrate Chromic hydroxide Chromic (III) hydroxide Chromic oxide, hydrous Chromium hydrate Chromium hydroxide Chromium (3+) hydroxide Chromium tri hydroxide Empirical CrHaOs Formula Cr(OH)3... 

Chromium hydroxide n. Cr(OH)3. Green pigment, manufactured by adding a solution of ammonium hydroxide to the solution of a chromium salt. Syn chromic hydrate and chromium hydrate. 

Chromic Hydrate See Chromium Hydroxide. Chromic Oxide See Chromium Oxide Green. 

Chromium(IH) chloride, chromic chloride, CrClj. Violet solid (Cr plus CI2, hydrate plus SOCI2) only soluble in water in presence of Cr. Forms many complexes including the hydrates [Cr(H20)6]Cl3 - violet, [Cr(H20)jCl]Cl2,H20 - green, [Cr(H20)4Cl2]Cl,2H20 - green. 

Chromium Hydroxide Green. This color additive is principally hydrated chromic sesquioxide [12182-82-0], -xHpD (Cl Pigment... 

Methyl ketones are important intermediates for the synthesis of methyl alkyl carbinols, annulation reagents, and cyclic compounds. A common synthetic method for the preparation of methyl ketones is the alkylation of acetone derivatives, but the method suffers limitations such as low yields and lack of regioselectivity. Preparation of methyl ketones from olefins and acetylenes using mercury compounds is a better method. For example, hydration of terminal acetylenes using HgSO gives methyl ketones cleanly. Oxymercuration of 1-olefins and subsequent oxidation with chromic oxide is... 

Chrom-hydrat, -hydroxyd, n. chromic hydroxide, chromium(lll) hydroxide, -hydroxydul, n. chromous hydroxide, chromium(II) hydroxide. 

Chromoxyd, n. chromium oxide, specif, chromic oxide, chromium(III) oxide. -farbe, /. chrome oxide color, -hydrat, n. chromium hydroxide, specif, chromic hydroxide, chro-mium(III) hydroxide, -natron, n. sodium chromite. -salz, n. chromic salt, chro-mium(III) oxide-... 

Since the natural passivity of aluminium is due to the thin film of oxide formed by the action of the atmosphere, it is not unexpected that the thicker films formed by anodic oxidation afford considerable protection against corrosive influences, provided the oxide layer is continuous, and free from macropores. The protective action of the film is considerably enhanced by effective sealing, which plugs the mouths of the micropores formed in the normal course of anodising with hydrated oxide, and still further improvement may be afforded by the incorporation of corrosion inhibitors, such as dichromates, in the sealing solution. Chromic acid films, in spite of their thinness, show good corrosion resistance. 

The following equations summarize the steps believed to occur when NaOH is slowly added to a solution of chromic ion. Step (4c) corresponds to formation of solid hydrated chromium hydroxide step (4d) corresponds to its dissolving in excess NaOH. 

Chromic hydroxide, Cr(OH)3, is a compound with low solubility in water. It is usually hydrated and does not have the definite composition represented by the formula. It is quite soluble either in strong acid or strong base. 

Chromic Perchlorate. Cr(C104)3, mw 350.30, OB to CrO HCI +28.5% only the hexahydrate has been prepd as blue-green delq crysts, mp 94° (Refs 1, 5 6) CA Registry No 13537-21-8 Preparation. By dissolving hydrated chromic oxide in 20% perchloric ac followed by-evapn of the soln (Ref 4)... 

Lucchi , who studied the oxidation of substituted benzaldehyde derivatives found that chlorine atoms in the meta and para position accelerate the reaction and alkyl groups retard the oxidation. A Hammett plot of Lucchi s data yields a good straight line with the slope p = 1.06. These data suggest that the reaction proceeds by way of the chromic ester of hydrated benzaldehyde as intermediate, viz. 

It was found by Chatterji and Mukherjee that the rate law for the oxidation of formaldehyde indicated that the chromic acid was esterified by the aldehyde hydrate formed, although they did not succeed in isolating the ester.The hypothesis of ester formation seems to be supported by the experience that the rate of reaction is increased by addition of pyridine. 

Chromate conversion coatings for aluminum are carried out in acidic solutions. These solutions usually contain one chromium salt, such as sodium chromate or chromic acid and a strong oxidizing agent such as hydrofluoric acid or nitric acid. The final film usually contains both products and reactants and water of hydration. Chromate films are formed by the chemical reaction of hexavalent chromium with a metal surface in the presence of accelerators such as cyanides, acetates, formates, sulfates, chlorides, fluorides, nitrates, phosphates, and sulfamates. 

Chromate is a strong oxidizing agent in acidic media and produces Cr(III) ions in the hydrate form, Equation 6. In neutral and basic media, chromate is a rather weak oxidizer, as evidenced by its negative oxidation potential (Equation 7), and the product is chromic hydroxide (8). 

Besides the amorphous alumina films formed in the majority of acidic electrolytes (except those formed in chromic acid and exhibiting traces of y-Al203194), there are possibilities of forming oxides with a more or less pronounced crystallinity. These oxides are formed in alkaline solutions195 and especially in sodium carbonate baths.196 According to the data provided by Hiroshi and Yoshimura,197 these oxides contain a y- A1203 phase easily hydrated and converted into a bayerite-like substance. 

The Cr/Si02 catalyst is made by spin-coat impregnation of the flat silica support with a solution of chromic acid in water. Figure 9.25 shows the Cr XPS spectrum of the catalyst after drying. Chromium is present as a hydrated Cr(VI) oxide, with a Cr 2p binding energy characteristic of chromate species, as the reference spectra in the lower half of the figure show. An essential step in the... 

The simple hydrated ionic salt, chromic nitrate, has a spectrum quite distinct from the ionic salts of cobalt and manganese. The principal peak shows a splitting. This may be related to the very strong aflSnity which chromium displays toward its first coordination sphere of water. 

Fio. 16. Spectra of chromic oxide and of chromic ion in a hydrated salt, in anion and in cation complexes. 

The anhydrous chromium (III) chloride may be obtained by heating the hydrated salt CrCls 6H2O with SOCI2 and subliming the product in a stream of chlorine at 600°C. Alternatively, the red-violet anhydrous chloride can be obtained by passing chlorine gas over a mixture of chromic oxide and carbon ... 

Formula Cr2(S04)s MW 392.16 several hydrates are known these include the pentadecahydrate Cr2(S04)s I5H2O and the octadecahydrate Cr2(S04)3-18H20 Synonym chromic sulfate... 

The other abrasive agents used are tin oxide, chromic oxide, sand, carbides (silicon carbide and boron carbide), zirconium silicate, zinc oxide, garnet, rouge (fine red powder of iron oxide), kieselgurh, tripoli, magnesium oxide, hydrated silica etc. 

---