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US 4,528,175 AGranted
Production of chromium (III) compounds
AssigneeAllied Corporation
InventorsJames F. Walther, John I. Choi
Life of this patent
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Abstract
A process of preparing chromium (III) compounds from chromate and/or dichromate salts by forming a mixture of such salts, an acid, water and a reducing agent. Additional acid is added to the mixture which is then cooled selectively precipitating the salt of the anion of the acid and the cation of the chromate and/or dichromate salts which is separated from the solution containing the desired chromium (III) compound.
Claims19
A process for preparing chromium (III) salts of the formula:
- Cr.sup.+3 .multidot.X.sup.-m.sub.n/2
- from an Alkali metal or Alkaline Earth metal chromate and/or dichromate or a mixture thereof, wherein;
- X is halide;
- m is 1;
- and
- n is 6;
- said process comprising the steps of:
- (A) forming a reaction mixture comprising one or more of the said chromate and/or dichromate salts, water, a reducing effective amount of reducing agent, and at least a stoichiometric amount of an acid or the formula H.sub.m X.sup.-m, and reacting said mixture for a time and at a temperature sufficient for chromium species in the +6 oxidation state to be reduced to the +3 oxidation state;
- (B) adding to said mixture of step (A) an acid identical to that used in step (A), or an anhydrous species capable of forming such acid in situ in an amount such that said mixture contains an amount of said acid equal to or greater than the amount of Cr.sup.+3 and Alkali metal or Alkaline Earth metal in said mixture;
- (C) cooling said reaction mixture thereby selectively precipitating salt of said Alkali metal or Alkaline Earth metal and the anion of said acid from said reaction mixture;
- and
- (D) separating said precipitated salt from said reaction mixture thereby forming an aqueous solution of Cr.sup.+3 .multidot.X.sup.-m.sub.n/2.
9 more elements
A process of preparing chromium (III) salts of the formula:
- Cr.sup.+3 X.sup.-m.sub.n/2
- from chromate and/or dichromate salts, wherein;
- X is a univalent, divalent or trivalent anion;
- m is 1, 2 or 3;
- and
- n is 2 when m is 3, n is 3 when m is 2, and n is 6 when m is 1;
- said process comprises the steps of:
- (A) forming a reaction mixture comprising said chromate and/or dichromate salts, water, a reducing effective amount of a reducing agent and at least a stoichiometric amound of an acid of the formula H.sub.m X.sup.-m, and reacting said mixture for a time and at a temperature sufficient for substantially all chromium species in the +6 oxidation state to be reduced to the +3 oxidation state;
- (B) adding to said mixture of step (A) an acid identical to that used in step (A), or an anhydrous species capable of forming such acid in situ in an amount such that said mixture contains an amount of said acid equal to or greater than the amount of Cr.sup.+3 and other cations in said mixture;
- (C) cooling said reaction mixture thereby selectively precipitating salt of the chromate or dichromate counter ion and anion of said acid from said reaction mixture;
- and
- (D) separating said precipitated salt from said reaction mixture thereby forming an aqueous solution of Cr.sup.+3 X.sup.-m.sub.n/2.
9 more elements
Dependencies are inferred from the claim text.