Earths

Earths, the name applied by the alchemists and earlier chemists to certain substances now known to be oxides of metals, which were distinguished by being infusible, and by insolubility in water. The term was made to include the oxides of calcium, strontium, and barium, which undergo chemical change by contact with water, and yield alkaline solutions. On account of this property these oxides were called the alkaline earths. The term earth is now disappearing from modern text-books of chemistry. See SOILS.