BORAX 421 



ground to a fine powder before beinj^ packed and shipped. 



The process generally used to make borax from ])oric acid 

 is briefly summarized as follows: Efjual quantities of crys- 

 tallized sodium carbonate and water are heated by steam in a 

 lead lined vessel, and to the solution thus obtained siillicicnt 

 boric acid is gradually added to combine with the sodium car- 

 bonate and form the borax salt (NaiBiOv), lOlLO. Another 

 process is to prepare sohitions of anmionia, sodium nitrate, 

 and boric acid in the proportions of two, one, and two, respec- 

 tively. By heating this mixture and dissolving in water, l)orax 

 and ammonium nitrate are formed. In ])oth of these cases 

 the crystals of borax are ultimately ol^tained by the evapora- 

 tion of the solutions containing the borax salt. 



At the borax refinery in Alameda, Cal., the process used 

 to convert colemanite into borax crj'stals is ])riefly outlined 

 as follows: The crude colemanite, obtahied direct from the 

 mines, is first broken into lumps of from three-fourths to \\ 

 inches in diameter, then reduced in a grinding mill to tlie size 

 of fine sand, and finally passed through rolls which grind the 

 material to the fineness of flour. The floured product is trans- 

 ferred to an iron tank partly filled with water containing in 

 solution the proper proportion of sodium carbonate necess;ir}^ 

 to decompose the calcium borate. (A ready and cheap sup- 

 ply of sodium carbonate is obtained from Owens Lake, Cal.) 

 Heat is applied to the tank and the contents boiled and thor- 

 oughly agitated by means of a mechanical agitator. After a 

 short time the chemical reaction has become completed, the 

 double decomposition being the change from calcium borate 

 and sodium carbonate to calcimu carbonate and sodium bo- 

 rate. The sodium borate being soluble is extracted from the 

 insoluble calcium carbonate by leaching with hot water, which 

 dissolves in addition a small quantity of other soluble salts 

 from the impurities in the ore and sodium carbonate. As a 

 consequence the crj'stals of borax obtained by cooling and 

 evaporating this solution in tanks are of a dark color and some- 

 what impure. They are purified by a second solution in hot 

 water and a second cry'staUization in a special vat having a 

 series of suspended wires on which the purer borax cr>'stals 

 form. The crystals on the sides and bottom of the vat are less 



