BORIC acid: it is a white crystalline substance slightly soluble in cold water ( 1.95 g in 100 g of water at 0 ° C ) and very soluble in boiling water ( 27.5 g 100 ° c ) This acid is extracted from certain volcanic origin natural waters, but also manufactured treating borax with sulfuric acid or hydrochloric acid. Boric acid is a mild antiseptic frequently incorporated into talcum powders. Used as a flux in soldering or Tan, the hardening of steel surfaces and glassware and locería industries.