Produced in US. the concentrate, mostly in foreign markets, for processing into refined borax and boric acid. The balance of the ore is shipped to the company’s refinery at Wilmington, Calif., where various refined products are made, including borax, anhydrous borax, and boric acid. PCB is putting finishing touches to an $18,000,000 expansion and modernization program. Part of the tab is for shifting from underground to open-pit mining, but a large portion is for a new concentrating plant and a new refinery at Boron to replace existing units. At the new refinery expected to start in the second half of this year, PCB will open-pit mine borax ore, dissolve it in recycling refinery end liquor, remove part of the insoluble shale in gigantic thickeners, and filter the resulting borax solution. Borax will then be crystallized from this solution as sodium tetraborate decahydrate or pentahydrate by controlling temperature in vacuum crystallizers. Dried borax will serve as feed material for further processing to boric acid and anhydrous borax. The third producer, West End Chemical, uses carbonation on Searles Lake brines in a process similar to American
700
SOURCE:
CHEMICAL ECONOMlCS HANDBOOK. STANDARD RESEARCH INST.
VOL. 49,
NO. 3
MARCH 1957
323
