"Alkali. (Arabic, al Kali.) A name applied to a well-defined class of bodies characterized by the following properties. They turn red blue, completely neutralize s, they are soluble in water, and their solutions exert a caustic action upon animal matter. The alkalies proper are the oxides of , sodium, , and cæsium. To these must be added the compound alkali , the oxide of the hypothetical metal , which used to be called the volatile alkali, in contradistinction to potash and soda, which were called fixed alkalies. The alkaline earths are the oxides of , , , and . The oxides of some other metals, such as silver, , and , are also somewhat soluble in water, and possess slight alkaline properties."