Synthesis of potassium chromate

Preparation of potassium chromate

Preparation of potassium chromate from potassium dichromate and potassium carbonate

If potassium dichromate is available potassium chromate could be obtained by reacting potassium carbonate with potassium dichromate:

Preparation of potassium chromate from potassium dichromate and potassium carbonate

Preparation of potassium chromate from potassium dichromate and potassium carbonate

30 grams of pulverized potassium dichromate are dissolved in 60 ml of boiling water. To the obtained solution, 18 grams of potassium carbonate dihydrate (K2CO3 · 2H2O) are added, while stirring. The reaction mixture is filtered and the filtrate is cooled to room temperature, the obtained crystals of potassium chromate are filtered and dried. The additional amount of potassium chromate crystals could be obtained by evaporating the filtrate.

Preparation of potassium chromate by fusing chromic oxide, potassium hydroxide, and potassium nitrate

Preparation of potassium chromate

Preparation of potassium chromate

An iron crucible is supported on a ring stand. 65 grams of solid potassium hydroxide are added into the crucible and heated until the potassium hydroxide is completely melted. Then the flame is removed and 50 grams of chromic oxide (Cr2O3) are added. The obtained mixture is stirred with an iron spatula and 50 grams of finely powdered potassium nitrate are added while stirring the mixture until a thin paste is formed. After all reagents have been added the mixture is heated again with 2 cm high flame and partially closed. The cover is removed at frequent intervals to prevent boiling over. After about 15 minutes heating the mixture becomes quite thick and is likely to froth over. To prevent this, the cover is removed and stirred, by protecting the hand against spattering. When the mass becomes solid, the crucible is heated again until it froths very little. Finally, the covered crucible is heated with the full flame for 20 minutes while stirring at frequent intervals and scraping any solid from the sides of the crucible into the hot mass. When the heating is finished and the solid has partially cooled, while still hot, the content of the reaction is scraped into a porcelain evaporating dish. The remaining residue in the crucible when it has cooled to room temperature is extracted with 300 ml of boiling water and the obtained solution is poured to the solid in the evaporating dish. The evaporating dish is heated until all the lumps have disintegrated and by allowing any sediment to settle and the obtained yellow solution of potassium chromate is decanted and filtered. The residue in the evaporating dish is additionally treated with 50 ml of boiling water, decanted and filtered. The combined filtrates are transferred to the porcelain evaporating dish and evaporated over a flame until crystals of crude potassium chromate begin to separate on the surface of the liquid. If a small amount of dark-colored solid separates during the evaporation, the solution should be filtered a second time. 50 ml of water are added to the hot solution and obtained solution is allowed to stand until a satisfactory crop of crystals has separated. The crystals from the cold solution are removed by filtration and allowed to dry at room temperature.

Synthetic inorganic chemistry, by A. A. Blanchard, 321-323, 1936

IUPAC Name

dipotassium;dioxido(dioxo)chromium

InChI

InChI=1S/Cr.2K.4O/q;2*+1;;;2*-1

InChI Key

XMXNVYPJWBTAHN-UHFFFAOYSA-N

Canonical SMILES

[O-][Cr](=O)(=O)[O-].[K+].[K+]

MeSH Synonyms

bipotassium chromate, dipotassium chromate, potassium chromate, potassium chromate(VI), potassium chromate(VI), 51Cr-labeled

Depositor-Supplied Synonyms

POTASSIUM CHROMATE, Bipotassium chromate, Dipotassium monochromate, Potassium chromate(VI), Dipotassium chromate, Tarapacaite, 7789-00-6, Chromate of potash, Chromate of potass, Chromic acid, dipotassium salt, Caswell No. 687, dipotassium dioxido(dioxo)chromium, Neutral potassium chromate, UNII-5P0R38CN2X, CCRIS 882, Potassiumchromate, Dipotassium chromate (K2CrO4), HSDB 1249, Potassium chromate (K2(CrO4)), EINECS 232-140-5, EPA Pesticide Chemical Code 068301, Chromic acid (H2CrO4), dipotassium salt, Potassium chromate solution, Chromic acid (H2CrO4), potassium salt (1:2), Potassium chromate [Chromium and chromium compounds], 18453-57-1, dipotassium salt, ACMC-20ajuy, (K2CrO4d, 51Cr-Potassium chromate, AC1L2NJN, AC1Q1TRI, dipotassium chromate(2-), dipotassium ion chromate(2-), KSC225A1F, POTASSIUM CHROMATE, ACS, 12249_RIEDEL, 31250_RIEDEL, 35157_RIEDEL, 529508_ALDRICH, 5P0R38CN2X, dipotassium dioxido-dioxochromium, 02673_FLUKA, 35157_FLUKA, CHEBI:75249, CTK1C5012, MolPort-006-109-845, XMXNVYPJWBTAHN-UHFFFAOYSA-N, 12249_SIAL, 31250_SIAL, dipotassium dioxochromiumbis(olate), 216615_SIAL, AKOS015902665, RTR-024932, TRA-0176351, LS-53391, S251, TR-024932, 3B4-1877, I14-19757, Chromium(VI) atomic spectroscopy standard concentrate 1.00 g Cr(VI)

Removed Synonyms

CHROMIC ACID, CID24597, potassium chromate(VI), 51Cr-labeled, C027373, 39322-04-8

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1 comment

  1. Fritz Haber

    If you want to prepare potassium dichromate insted of potassium chromate, just acidify the filtrate with sulfuric acid until it turns bright red. Then proceed as described above.
    Other oxidizing agents like chlorates, perchlorates etc. could also be used instead of the nitrate.

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