[Ital.] A substance formerly got from sea-weeds, and in 1791 it was produced from common salt by Le Blanc. In this process salt is transformed into sodium sulphate by adding sulphuric acid ; then by mixing with chalk and coal it is made into sodium carbonate. Soda can be produced by electricity from brine. It is the most important of all chemical products used in the industries. Caustic soda, or sodium hydroxide, is used in making soap, wood pulp for paper, etc.; cooking or washing soda is sodium bicarbonate.