They are obtained by neutralizing the solution of the acid, or by fusing the oxide with potassium carbonate and treating the melt with hydrofluoric acid.
Potassium chromate, K2Cr04, may be prepared by neutralizing a solution of potassium bichromate with potassium carbonate or with caustic potash.
Telluric acid, H2Te04, is obtained in the form of its salts when tellurium is fused with potassium carbonate and nitre, or by the oxidizing action of chlorine on a tellurite in alkaline solution.
Potassium iridium sesquichloride, K 3 IrC1 6.3H 2 O, is obtained by passing sulphur dioxide into a suspension of potassium chloriridate in water until all dissolves, and then adding potassium carbonate to the solution (C. Claus, Jour.
All commercial caustic potash is contaminated with excess of water (over and above that in the KHO) and with potassium carbonate and chloride; sulphate, as a rule, is absent.
A better method is Wohler's, in which the finely powdered mineral is fused with twice its weight of potassium carbonate in a platinum crucible, the melt powdered and treated in a platinum basin with aqueous hydrofluoric acid.
The hydrosulphide, KHS, was obtained by Gay-Lussac on heating the metal in sulphuretted hydrogen, and by Berzelius on acting with sulphuretted hydrogen on potassium carbonate at a dull red heat.
A variety of animal charcoal is sometimes prepared by calcining fresh blood with potassium carbonate in large cylinders, the mass being purified by boiling out with dilute hydrochloric acid and subsequent reheating.
The solution is strongly caustic. It turns yellow on exposure to air, absorbing oxygen and carbon dioxide and forming thiosulphate and potassium carbonate and liberating sulphuretted hydrogen, which decomposes into water and sulphur, the latter combining with the monosulphide to form higher salts.
Thiosemicarbazide, NH 2 CS NH NH 2, prepared from hydrazine sulphate, potassium carbonate and thiocyanate (N.