Polonium nitrates

P0O2 is obtained by direct combination of the elements at 250° or by thermal decomposition of polonium(IV) hydroxide, nitrate, sulfate or selenate. The yellow (low-temperature) fee form has a fluorite lattice it becomes brown when heated and can be sublimed in a stream of O2 at 885°. However, under reduced pressure it decomposes into the elements at almost 500°. There is also a high-temperature, red, tetragonal form. P0O2 is amphoteric, though appreciably more basic than Te02 e.g. it forms the disulfate Po(S04)2 for which no Te analogue is known. 

Fusion of polonium dioxide with potassium hydroxide in air, or with potassium nitrate, gives a colorless melt the solubility of the polonium after this treatment corresponds with the solubility data for potassium polonite (12). 

Studies of the solubility of polonium(IV) in formic, acetic, oxalic and tartaric acids have provided evidence of complex formation,48 with the acetato complex emerging as more stable than the hexachloro anion. Other studies of the solubility of polonium(IV) hydroxide in carbonate49 and nitrate50 solution, together with investigations51 of the ion exchange behaviour of polonium(IV) at high nitrate ion concentration, have been discussed in terms of the formation of anionic complex species. 

Tellurium dissolves in concentrated nitric acid. On evaporation colourless rhombic Te203(0H)3N03 crystallises. Polonium also forms a somewhat similar nitrate whose composition is as yet unknown. 

Polonium metal was formed by the reduction of P0CI4, P0OCI2 as well as from the nitrate or the acetate. The solvents involved were hydrochloric acid and polar organics such as acetone, ethanol, and methyl ethyl ether. Mercury served as the reducing agent and a polonium-mercury amalgam is formed. 

Thorium, bismuth and polonium can be quantitatively separated from lead.(and radium) by extraction from a saturated aluminum nitrate solution with-mesityl oxide (M3)i Thallium can be separated by extraction of thallium III into a solution of 5% n-octanol In hexone from 0.15 M hydrochloric acid (L2). 

From a solution containing iron and some rare earth metals, Debierne precipitated a mixture of hydroxides. It was radioactive, an activity that could not have its origin in uranium, radium or polonium. A new element could be isolated by fractional crystallization of magnesium lanthanum nitrate. The element was named actinium after the Greek word aktinos, meaning ray . Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300°C. 

Estimation of Radioactivity.— The 8-ray activity of the lead used indicates that it contains in about 2 parts so-called radium G and 1 part lead, an amount of radium D of the order of 10 parts. This is betrayed by the steady growth of a penetrating jS-ray product (RaE) which comes to practical equilibrium with its parent in about a month after they are separated. Evidently the ionization— if the a-rajre from the polonium present are cut off—caused by a weighed amount of the material imder constant conditions, is a measure of the concentration of radium D relative to its isotopes radimn G and lead. Thus the determination of the activity of the end fractions gives information as to the relation between the solubility of the nitrate of radium D and the mean solubility of the nitrates of radium G and ordinary lead, a relation of great interest because it cannot be tested by atomic weight determinations. This case should afford an especially favorable test of the theory of complete identity. 

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