Chromic oxide hydrous

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. 

Chromic Hydroxide. Chromium hydroxide, chromic oxide gel chromic oxide, hydrous. CrH3Oj mol wt 103.03. Cr 50.48%. H 2-93%, O 46.59%. Cr(OH)j. Occurs only as hydrates. Prepn Ruthroff, Inorg. Syn. 2, 190 (1946) Hein, Herzog in Handbook of Preparative Inorganic Chemistry vol. 2, G- Brauer, Ed, (Academic Press, New York, 2nd ed- 1965) pp 1345-1346. 

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... 

Mixed gels of hydrous ferric and chromic oxides were prepared by the addition of an equivalent amount of ammonium hydroxide to mixtures of the solutions of ferric nitrate (0.5M with respect to Fe20j) and chromic nitrate (0.5M with respect to Cr203). The dual gels were washed free of nitrate ions and air- or oven-dried. A series of mixtures corresponding to 20, 40, 60, and 80% Fe203 was prepared. 

Cr2 03 - 112 0, of indefinite composition occurs. This compound is commonly misnamed as chromic or chromium (ITT) hydroxide [1308-14-1], Cr(OH)2. A tme hydroxide, chromium (ITT) hydroxide trihydrate [41646-40-6], Cr(OH)2 3H20, does exist and is prepared by the slow addition of alkaU hydroxide to a cold aqueous solution of hexaaquachromium(III) ion (40). The fresh precipitate is amphoteric and dissolves in acid or in excess of hydroxide to form the metastable Cr(OH). This ion decomposes upon heating to give the hydrous chromium (ITT) oxide. However, if the precipitate is allowed to age, it resists dissolution in excess hydroxide. 

Both positively and negatively charged colloids have been prepared. The former results when the hydrated oxide is pejotised with chromic chloride, or may be formed by hydrolysis of the chloride or nitrate the latter is prepared by peptising the hydrous oxide with sodium or potassium hydroxide, or by adding sodium hydroxide to chromium nitrate solution in presence of arsenious acid and then dialysing. ... 

There are many similarities (e.g., in charge storage and electro-chromic behavior, and in transport mechanisms) between inorganic hydrous oxide films and the largely organic redox polymer-modified electrodes which are also of much interest at the present time. Of special interest is the appearance in certain instances240 with the... 

Hydrous chromium oxide was precipitated from a 0.1 JV solution of chromic nitrate by the slow addition with stirring of 0.1 AT ammonia water. The filtered, washed gel was then slowly dehydrated in an atmosphere of hydrogen, the temperature being gradually raised over a period of weeks until dehydration was substantially complete. 

According to the chemical literature, iron(III) dichromate(VI), Fe2(Cr207)3, is used as a water-soluble pigment and is obtained by heating aqueous chromic acid with hydrous iron(III) oxide Colour Index, 1971 MacIntyre, 1992). Related compoimds also used as pigments are iron chromate, Fe2(Cr04)3, and iron chromate hydroxide, Fe(OH)Cr04 (qq.v.). 

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