III Sulfate 18-Hydrate

Submitted by Sherlock Swann, Jr., Theodore S. Xanthakos, and Richard Strehlow  

Cobalt(III) sulfate has been prepared from cobalt(II) sulfate by electrolytic oxidation1 and by treatment with ozone2 or fluorine.3 The electrolytic oxidation of a saturated solution of cobalt(II) sulfate in 10 N sulfuric acid at 5 to 10° 1 gives cobalt(III) sulfate 18-hydrate. Under these conditions, this compound is insoluble and does not decompose rapidly. 

4- by 10-cm. sheet of thin copper and is bent to fit snugly into a 1-1. tail-form beaker. 

One-milliliter samples of the suspension are pipetted into measured excess volumes of standard oxalic acid solution. Each sample is diluted to 100 ml., and the unoxidized oxalic acid is then titrated with 0.1 N potassium permanganate solution which has been standardized against oxalic acid. Since the concentration of crystals in the anolyte is not absolutely uniform, the material yield calculated from the quantity of oxidizing agent present depends upon the region from which the sample is taken. Larger samples are analyzed electrometrically because of the indefiniteness of the visual end point.1 

Crystals of cobalt(III) sulfate 18-hydrate decompose at room temperature within a few hours, but they can be stored in a refrigerator for 3 to 4 days without decomposing noticeably. Aqueous solutions of the compound evolve oxygen, the reaction occurring instantaneously in warm water and rapidly even in cold water. Suspensions in cold 10 N sulfuric acid decompose very slowly. Cobalt(III) sulfate oxidizes many organic compounds very vigorously.1 

---

Co(NH3)6](N03)3 Hexammineco-balt(III) nitrate, 2 218 [Co(NH3)6]2(C204)3-4H20 Hexam-minecobalt(III) oxalate, 2 220 CoNO(CO)3 Cobalt nitrosyl tricarbonyl, 2 238, 239 Co2(S04)3-18H20 Cobalt (III) sulfate 18-hydrate, 5 181 Cr(CN)sK3 Potassium hexacyano-chromate(III), 2 203 Cr (CO) t Chromium hexacarbonyl, 3 156... 

---