A white or gray crystalline salt, with a slight alkaline taste, used as a flux, in soldering metals, making enamels, fixing colors on porcelain, and as a soap. It occurs native in certain mineral springs, and is made from the boric acid of hot springs in Tuscany. It was originally obtained from a lake in Thibet, and was sent to Europe under the name of tincal. Borax is a pyroborate or tetraborate of sodium, Na2B4O7.10H2O.
- A hydrated sodium borate, Na2B4O7·10H2O, an ore of boron, that is used as a cleaning compound.
- An anhydrous sodium borate used in the manufacture of glass and various ceramics.
- Cheap merchandise, especially tasteless furnishings: "today's glinty borax” ( New Yorker).