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Hydrated chromium(III) sulfate, Cr 2 (SO 4) 3 ·15(H 2 O), (CAS #10031-37-5) is a green solid that also readily dissolves in water. It is obtained by heating the 18-hydrate material above 70 °C. Further heating yields the anhydrous sulfate. A variety of other chromium(III) sulfates are known, but also contain hydroxide or oxide ligands.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
Commercially available chromium(III) chloride hydrate is the dark green complex [CrCl 2 (H 2 O) 4]Cl. Closely related compounds are the pale green [CrCl(H 2 O) 5]Cl 2 and violet [Cr(H 2 O) 6]Cl 3. If anhydrous violet [10] chromium(III) chloride is dissolved in water, the violet solution turns green after some time as the chloride in the inner ...
The actual chemistry of [Cr(H 2 O) 6] 3+ is more complex in the tanning bath rather than in water due to the presence of a variety of ligands. Some ligands include the sulfate anion, the collagen's carboxyl groups, amine groups from the side chains of the amino acids, as well as "masking agents."
Solutions of metal aquo complexes are acidic owing to the ionization of protons from the water ligands. In dilute solution chromium(III) aquo complex has a pK a of about 4.3, affording a metal hydroxo complex: [Cr(H 2 O) 6] 3+ ⇌ [Cr(H 2 O) 5 (OH)] 2+ + H + Thus, the aquo ion is a weak acid, of comparable strength to acetic acid (pK a of about ...
To prevent the energy-consuming change in oxidation state, the use of chromium(III) sulfate is under development; for most applications of chromium, the previously established process is used. [ 64 ] In the chromate conversion coating process, the strong oxidative properties of chromates are used to deposit a protective oxide layer on metals ...
Soluble hexavalent chromium is the most common type of chromium in oceans, where over 70% of dissolved chromium in the ocean is found in oxyanions such as chromate (CrO 2− 4). Soluble trivalent chromium is also found in the oceans where complexation with organic ligands occurs. Chromium is estimated to have a residence time of
Iron(III) chloride hexahydrate: FeCl 3 ·6H 2 O yellow/brown Iron(III) chloride anhydrate: FeCl 3: black Chromium (III) sulfate: Cr 2 (SO 4) 3: dark green Copper(II) sulfate anhydrate: CuSO 4: white Copper(II) sulfate pentahydrate: CuSO 4 ·5H 2 O blue Copper(II) benzoate: Cu(C 7 H 5 O 2) 2: blue Cobalt(II) chloride: CoCl 2: dep blue Cobalt(II ...