Preparation of manganese(II) chloride (manganous chloride)
The waste liquors left after the generation of chlorine from manganese dioxide and hydrochloric acid contain principally manganous chloride.
Besides this, however, there is always some free hydrochloric acid and if manganese dioxide was used of technical grade almost always a considerable amount of iron ions present. The greater part of the free hydrochloric acid can be removed by evaporating the solution until a pasty mass of manganese(II) chloride is left which will solidify on cooling. The iron can be removed from the solution of this residue by virtue of the ease with which ferric salts hydrolyze. The nearly neutral solution is treated with suspended manganous carbonate (obtained by treating a part of the solution itself with a soluble carbonate). Ferric chloride hydrolyzes according to the reversible reaction, FeCl3 + 3H2O → 3HCl + Fe(OH)3. In the presence of manganous carbonate the small amount of free hydrochloric acid thus formed is continuously used up according to the reaction MnCO3 + 2HCl → MnCl2 + H2O + CO2. Thus, the reaction of hydrolysis is enabled to run to completion. The remaining solution, which is neutral and entirely free from iron salts, yields crystallized manganese(II) chloride, MnCl2 • 4H2O, upon evaporation.
250 ml of waste manganese liquor are boiled in a porcelain dish until the residue becomes pasty. The mixture should be stirred with a glass rod in order to prevent from spattering until it becomes semi-solid. The residue is heated to boiling with 750 ml of water and without filtering the solution, 1/10 of this solution is diluted to 1,000 ml in and a solution of sodium carbonate is added to it until all the manganese is precipitated as carbonate. The manganese(II) carbonate is allowed to settle and washed by decantation at least four times with water. The solid manganese(II) carbonate is added to the remaining 9/10 of the manganese(II) chloride solution, and the mixture is boiled until a few drops of the filtered liquid give no red color when tested with potassium thiocyanate. Then the solution is filtered and evaporated until a crystal scum forms on blowing across the surface. The solution is cooled slowly by allowing to crystallize and leaving for at 12-24 hours. The obtained crystals of manganese(II) chloride are filtered and the mother liquor is evaporated yielding further crops of manganese(II) chloride until practically all the salt has crystallized. The crystals of manganese(II) chloride are dried. Manganese(II) chloride is deliquescent when the temperature is low and the atmosphere charged with moisture. If the manganese(II) chloride cannot be obtained satisfactorily by the above directions, the crystallization and drying is performed in a place at a slightly elevated temperature, 25° C to 30° C; or by cooling the saturated hot solution rapidly by stirring or shaking, and drying the crystal meal so obtained by rinsing it with alcohol and then letting the ethanol to evaporate rapidly.
Synthetic inorganic chemistry, by A. A. Blanchard, 336-338, 1936
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Manganese(II) chloride, Manganous chloride, Manganese bichloride, Manganese dichloride, Scacchite, dichloromanganese, Manganese chloride (MnCl2), Manganese(II) chloride (1:2), Manganese chloride anhydrous, CCRIS 6882, HSDB 2154, NSC 9879, EINECS 231-869-6, MnCl2, Mangandichlorid, Sacchite, manganous dichloride, dichlorure de manganese, AC1L2NGR, Manganese standard solution, WLN: MN G2, Manganese chloride, (MnCl2), 244589_ALDRICH, 328146_ALDRICH, 416479_ALDRICH, 429449_ALDRICH, 450995_ALDRICH, CHEBI:63041, 20603-88-7 (dihydrate), NSC9879, 13446-34-9 (tetrahydrate), NSC-9879, AKOS015904054, LS-89205, 3B4-1977, I14-18148, Manganese atomic spectroscopy standard concentrate 10.00 g Mn
MANGANESE CHLORIDE, manganese(II) dichloride, manganese(2+) dichloride, Manganese(II) chloride solution, UNII-6YB4901Y90, CID24480, Manganese(II) chloride 0.1 M solution, Additive Screening Solution 26/Fluka kit no 78374, 7773-01-5, Manganese atomic spectroscopy standard concentrate 1.00 g Mn, 111283-62-6