Chromium(III) hydrolysis constants and solubility of chromium(III) hydroxide

Journal Article · Wed Feb 11 04:00:00 EST 1987 · Inorg. Chem.; (United States)

DOI:https://doi.org/10.1021/ic00250a002· OSTI ID:6772597

Rai, D; Sass, B M; Moore, D A

The solubility of freshly precipitated Cr(OH)/sub 3/ was determined in 0.01 M perchlorate solutions over a pH range of 3.8-14 and under a nitrogen atmosphere. Chromium concentrations in 0.0018-..mu..m filtrates at times between 6 and 134 days, when the solubility was approached from both the undersaturation and oversaturation directions, showed that equilibrium is attained in < 6 days below pH 12 and in approx. 63 days above pH 12. X-ray diffraction analyses of the solids showed that freshly precipitated Cr(OH)/sub 3/ was amorphous and remained amorphous throughout the equilibration period. Chromium hydroxide exhibits amphoteric behavior, with a minimum solubility between pH 7 and 10. On the basis of the solubility of Cr(OH)/sub 3/(s) as a function of pH, CrOH/sup 2 +/, Cr(OH)/sub 3//sup 0/, and Cr(OH)/sub 4//sup -/ were determined to be the dominant aqueous species in different pH regions. Thermodynamic equilibrium constants for the reaction are presented. No evidence for Cr/sup 3 +/, Cr(OH)/sub 2//sup +/, or any polynuclear complexes was observed, even in solutions heated to 60 and 90/sup 0/C, where polynuclear species are expected to form more rapidly. Although it is not possible to determine from these experiments the absolute value of the hydrolysis constants for reactions involving Cr(OH)/sub 2//sup +/ and Cr(III) polymeric species, the results do not set upper limits for the hydrolysis constants. 19 references, 4 figures, 3 tables.

• Research Organization: Pacific Northwest Labs., Richland, WA
• OSTI ID: 6772597
• Journal Information: Inorg. Chem.; (United States), Journal Name: Inorg. Chem.; (United States) Vol. 26:3; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CHROMIUM HYDROXIDES
COHERENT SCATTERING
DATA
DECOMPOSITION
DIFFRACTION
EXPERIMENTAL DATA
HYDROGEN COMPOUNDS
HYDROLYSIS
HYDROXIDES
INFORMATION
KINETICS
LYSIS
NUMERICAL DATA
OXYGEN COMPOUNDS
PH VALUE
REACTION INTERMEDIATES
REACTION KINETICS
SCATTERING
SOLUBILITY
SOLVOLYSIS
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION