ICBCOB Ca( OH) 2 2KOH CaC0s.
The calcium carbonate (CaCOB) that is formed at the same time is practically insoluble and may be removed by filtration. The solution is then evaporated to dryness and the resulting hydrate of potassium is finally melted and cast into sticks in metallic molds. Potassium hydrate is a white substance, absorbing moisture from the air with great readiness and also taking up carbon dioxide gas from the air, being thereby converted into the acid carbonate. The hydrate dissolves in half its own weight of water, the solution being intensely alkaline. The solid hydrate has powerful cauterizing properties (whence the name °caustic potashs) and de stroys the skin when brought in contact with it. It is used in the arts and in, the laboratory for a great variety of purposes.
The bromide of potassium (KBr) and the iodide (KI) are soluble, crystallizable salts, i which are largely used in medicine and in photography. The bromide may be prepared by adding bromide to a solution of potassium hydrate, the reaction being 6KOH -1- 6Br = 5KBr KBrO, 3H30.
To remove the potassium bromate (KBrO,) that is formed, the solution is evaporated to dryness after the addition of a small quantity of powdered charcoal and the dry residue is well pulverized and finally raised to a dull red heat. The carbon that is present then reduces the bromate to potassium bromide and free carbon dioxide gas. When this process is complete, the mass is cooled and redissolved in water, after which the pure bromide of potassium is pre pared by evaporation and crystallization. Iodide of potassium may be obtained in a similar man ner. Potassium chlorate, KC101, which is used in the laboratory for effecting oxidations and also as a source of free oxygen and which is likewise employed in medicine, may be prepared by passing chlorine gas through a warm, con centrated solution of potassium hydrate; chloride of potassium being formed at the same time, as is indicated by the equation