202 



slightly modified. The powdered ore, after being roasted at 

 a dull red heat for some time, was treated with hot dilute 

 sulphuric acid to remove the bulk of the copper and some 

 of the iron. This sulphuric acid solution was tiltered oft' from 

 the insoluble residue, and most of the copj^er electrolyzed out 

 of it, using a platinum anode. As the copper contents of 

 the solution decreased, a small amount of precipitate separat- 

 ed out. At the conclusion of the operation this was washed 

 by decantation, and heated with dilute nitric acid to remove 

 some metallic copper which had fallen from the cathode. 

 After being again washed, this was dried, ignited at a low 

 temperature, and tested. Its activity was about 5. Mean- 

 time the residue insoluble in sulphuric acid was treated with 

 nitric acid, and the portion remaining insoluble after this 

 treatment was filtered oft', washed, and tested. Its activity 

 was very low, much less than that of the original ore. The 

 solution was evaporated down, and as evaporation proceeded 

 a light-coloured rather bulky precipitate separated out. This 

 was filtered off from the solution before the concentration was 

 sufficiently great for crystallization to take j^lace on the solu- 

 tion being allowed to cool. The evaporation of the solution 

 was then continued to dryness on an air-bath. The mass was 

 re-dissolved in water and allowed to stand for some time; a 

 small amount of jDrecipitate settled down from this. The 

 solution was finally evaporated down again, a few c.c. of sul- 

 phuric acid added, and the heating continued until fumes 

 were freely given off. This treatment yielded a third lot of 

 precipitate, but its activity was low, and the amount obtained 

 negligible. Practically all the activity comes out with the 

 first crop from the nitric acid solution. About '6 gramme of 

 sulphate was obtained in this w^ay from the kilogramme of 

 ore, its activity being about 9. This sulphate is practically 

 insoluble in hot or cold hydrochloric acid, and only very 

 slowly soluble in nitric acid or aqua regia. It goes readily 

 into solution, however, in warm nitric acid on the addition 

 of a little chlorate of potash. The crude sulphate was 

 therefore dissolved in this way, and freed from a little silica 

 that had gone into solution on treating the ore with nitric 

 acid; the sulphate was then re-precipitated. 



The washed sulphate was digested for some hours with 

 warm ammonium acetate solution, and the greater part of it 

 dissolved readily. The insoluble portion was thoroughly wash- 

 ed, dried, and tested. Its activity was determined to be about 

 200 ; "02 gramme of this was forwarded to Professor Bragg for 

 examination, and his measurements of tlie rate of decay of 

 the induced activity from this indicated that the major part 

 of the activity was due to radium. This purified sulphate 

 is of low specific gravity, and is bluish -white in colour when 



