The Specific Radioactivity of Thorium and the Variation of the Activity With Chemical Treatment and With Time.

Abstract

rays and the inactive product which finally produces radium; the second, much slower change, giving -rays and actinium, thus: /(?)»->Ra »-etc.

The discovery of the elements. XIX. The radioactive elements

“…He computed that the undiscovered member ought to have a half-life period of five and one-half years, and two chemists at the University of Chicago, Herbert Newby McCoy and William Horace Ross, later verified this prediction. The new element was at first called mesothorium, but is now known as mesothorium 1 (20), (63), the name having been changed because Hahn afterward found that mesothorium 1 disintegrates into a short-lived product, mesothorium 2. Soddy's brilliant elucidation of the chemistry of mesothorium 1 led to his theory of radioactive isotopes, for which he was awarded the Nobel Prize (66).…”

History of the Unraveling of the Natural Decay Series

“…Boltwood noticed a radioelement was chemically similar to thorium [26] and suggested the name ionium [27], It was also shown that thorium X, actinium X, mesothorium I and thorium are chemically identical and are members of the alkaline-earth group of elements [28,29]. Inseparable pairs were thorium and radiothorium [30], radium and mesothorium, and RaD and lead [31][32][33]. Ionium, radiothorium, radioactinium and thorium were also chemically identical [34].…”

The Analytical Aspects of Thorium Chemistry.

“…As a consequence, they are of no technical importance and are useful only for the laboratory concentration of the element. Among these precipitante are sodium acetate from acetic acid solutions (25,163), guanidine carbonate (51), hydrofluoric acid or soluble fluoride (75), ammonium vanadate (194,195), ammonium molybdate (179), sodium tungstate (194,195), and potassium chromate (172,192,223) or dichromate (223). Original reports (179) of the completeness of the molybdate separation have been questioned recently (10a), but it is probably the most effective of those listed.…”

“…Its effectiveness is said to equal that of fumaric acid, although two precipitations from neutral solution are required for complete separation (194,195). Many investigators have employed this method to advantage (3,96,146,172). Use of sebacic acid appears to be equally effective in nearly neutral boiling solutions (222), although it is complicated by precipitation of rare earth sebacates at high sebacate-ion concentrations, e.g., with ammonium sebacate (248), and by precipitation of cerium when present in high concentrations (136).…”

“…As with fumaric acid, a second precipitation is necessary to free the product completely from rare earth elements. In the hands of Kolb and Ahrle (146) and McCoy and Ross (172) the method has yielded excellent results, and both Ashman (3) and Girotto (96) have applied it successfully to the estimation of thorium in minerals. Use of m-nitrobenzoic acid or fumaric acid seems to be a matter of choice.…”