The reduced solution is separated from the ore by filtration or decantation, and is treated with such a quantity of finely pulverized limestone as calculation has shown will bring it to the point at which uranium, vanadium, and copper will just begin to be precipitated, calcium sulphate being formed. The sulphuric acid from the sulphur dioxide is also available for the treatment of additional quantities of ore. Reduction of the iron to the ferrous state is an advantage, because in the subsequent precipitation of the uranium and vanadium less iron is precipitated, and the valuable metals are therefore in a more concentrated form. This treatment reduces the iron and the vanadium. The nearly neutral stock solution, containing uranium, vanadium, iron, and possibly copper, is then treated with sulphurous acid by subjecting the solution to the action of sulphur dioxide obtained by roasting sulphur or sulphide ores. The resulting acid washings are then strengthened by the addition of sulphuric acid until they contain, preferably 15 to 20 per cent of the acid, and are utilized for continuing the process. The ore residues from the treatment with sulphuric acid, as well as the residues from the similar treatment of the enriched ore, are freed from remaining values by being washed with dilute sulphuric acid. The enriched ore that has served for the neutralization of the acid solution, either alone or mixed with fresh ore, is treated with sulphuric acid, as described above, yielding an acid solution, which, after neutralization, is added to the stock solution. If necessary, the neutral solution is again clarified, and constitutes a part of the stock solution suitable for further treatment. At the same time, a part of the uranium, vanadium, and iron is precipitated on the ore as basic sulphates or carbonates, the effect of this precipitation being to enrich the ore, which may be of low grade. The resulting clear, acid solution is then brought into contact with fresh ore, heated, and agitated, the solution being thereby neutralized. The resulting acid solution contains the uranium, vanadium, and copper, if copper is present, and is preferably filtered or otherwise clarified. sulphuric acid diluted to 15 to 20 per cent is sufficient for the treatment of 1 ton of ore. The ore is crushed, preferably to 20 to 40 mesh, by any suitable means, and is agitated with hot sulphuric acid of 15 to 20 per cent concentration, the proportion of acid used depending upon the quality of the ore. The Fleck, Haldane, and White patent claims that radium, uranium, and vanadium can be extracted successfully in the following way: Method of Fleck, Haldane, and White Leaching With Sulphuric AcidĪ number of patents have been issued in connection with the use of sulphuric acid. In the method involving the use of an acid leach, the two acids employed up to the present are sulphuric and hydrochloric. These different methods have been discussed at some length in Bulletin 70, but are described here in more detail. The different methods heretofore used may be classified under three general heads, as follows: (1) Use of an acid leach (2) use of an alkaline leach followed by an acid leach (3) fusing the ore with some material that will break up the ore and make the extraction of the valuable contents possible. Consequently, there is a real need of the presentation of all of the necessary details in the successful treatment of uranium ores, and the refining of the finished products. The effect has been rather to discourage those who might have been inclined to invest money in the production and sale of radium. Therefore persons interested in methods of extracting radium have had little to guide them, as details of the methods in use have been closely guarded. Until recently little had been published on methods of treating any of the uranium ores for the extraction of radium, although a number of patents have been issued both in this country and abroad.
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