The New Student's Reference Work/Potassium

Potassium (pō̇-tăs′sĭ-um), a bluish-white metal discovered by Sir Humphrey Davy in 1807. It is the lightest of all the metals except lithium, and, as its specific gravity is only .865, it readily floats on water. In so doing it reacts violently with the water, forming caustic potash and giving off hydrogen, which ignites spontaneously from the heat of the reaction. At 32° F. it is brittle, like glass; at 59° it is soft and malleable; at 144° it becomes liquid. Potassium is widely diffused in the vegetable, animal and mineral kingdoms. Some of the more important potassium compounds are caustic potash (the hydroxide), the carbonate, the bicarbonate; also potassium chloride, bromide, iodide, nitrate (saltpeter), sulphate, chlorate, cyanide etc. Of these iodide, bromide and chlorate are used for medicines, the others being employed more or less in the arts.