_Borax._--A good deal of the Tuscan boric acid is used in France for the manufacture of borax, which is a sodium salt of boric acid. Borax is also manufactured from boronitrocalcite, a calcium salt of boric acid, which is found in Chili and other parts of South America. The crude boronitrocalcite or "tiza" is boiled with sodium carbonate solution, and, after settling, the borax is obtained by crystallisation. Borax itself is found in California and Nevada, U.S.A., and also in Peru, Ceylon, China, Persia, and Thibet. The commercial product is obtained from the native borax (known as "tincal") by dissolving in water and allowing the solution to crystallise. The Peruvian borax sometimes contains nitre. For testing the purity of refined borax the following simple tests will usually suffice. A solution of the borax is made containing 1 part of borax to 50 parts of water, and small portions of the solution are tested as follows: _Heavy metals_ (_lead_, _copper_, etc.).--On passing sulphuretted hydrogen into the solution, no coloration or precipitate should be produced. _Calcium Salts._--The solution should not give a precipitate with ammonium oxalate solution. _Carbonates._--The solution should not effervesce on addition of nitric or hydrochloric acid. _Chlorides._--No appreciable precipitate should be produced on addition of silver nitrate solution and nitric acid. _Sulphates._--No appreciable precipitate should be produced on adding hydrochloric acid and barium chloride. _Iron._--50 c.c. of the solution should not immediately be coloured blue by 0.5 c.c. of potassium ferrocyanide solution.