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.