CHANGES IN TREATMENT PRACTICE
The general method of treatment employed until quite recently has involved leaching the concentrate with concentrated sulphuric acid, thus getting the thorium, cerium, and other rare earths in solution and separating them from the silica, zircon, ilmenite and other insoluble products. From this stage different companies used slight variations in practice, such variations being kept strictly secret, although they all involved the precipitation of the thorium as oxalate by means of oxalic acid.
At the outbreak of the war the price of sulphuric acid went to four or five times the original cost, and the increased price of oxalic acid was practically prohibitive. Consequently the manufacturing companies had to change their entire procedure and to use chemicals that they could obtain at a reasonable price. In this difficult undertaking the companies were successful, and at least one company devised a process that was considerably more efficient than the old one.
At present mesothorium is being produced as a by-product by the Lindsay Light Co. and the Welsbach Co., the process used by the latter company having been originated by the Colorado Station of the United States Bureau of Mines. This process is cheap and extremely efficient, and will no doubt enable the Welsbach Co. to compete commercially with any other manufacturer of mesothorium. Of course as the process was developed by the Bureau of Mines it will ultimately be made available for anyone, but as mesothorium can only be made at a profit as a by-product of thorium nitrate, anyone who manufacturers mesothorium must first establish a thorium industry.