Polonium hydroxide solubility

A white solid, possibly polonium tetrafluoride, is obtained by treating polonium hydroxide or tetrachloride with dilute aqueous hydrofluoric acid treatment of this solid, in suspension in dilute hydrofluoric acid, with sulfur dioxide yields a bluish grey product (possibly PoF2) which rapidly reverts to the original white solid on standing, presumably owing to radio-lytic oxidation 12). The solubility of polonium(IV) in aqueous hydrofluoric acid increases rapidly with acid concentration, indicating complex ion formation (/ft), p. 48). 

The treatment of polonium hydroxide with 2 N formic acid yields a black solid of uncertain composition and low solubility (11). 

An unidentiffed compound, not polonium hydroxide and presumed to be P0OCI2, was obtained by the evaporation of a dilute hydrochloride acid containing polonium. The residue is soluble in polar organic solvents such as ethanol, ethylene glycol, dioxane, acetone, and methyl ethyl ketone. It is insolnble in benzene or chloroform. 

Fusion of polonium dioxide with a potassium chlorate/hydroxide mixture gives a bluish solid (colorless when hot) which is more soluble in water than the corresponding polonite (Po032 ) this presumably contains some potassium polonate. The trioxide may possibly be formed by strongly heating polonium dioxide and chromium trioxide in air (12). 

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). 

Metallic polonium is not affected by 15% bromic acid, even at 70°C, and polonium dioxide or polonium(IV) hydroxide are only slightly soluble (2.5 mg Po02/liter) in 10% bromic acid. Polonium tetrachloride is converted to a white solid of unknown composition by 15% bromic acid this could be a basic chloride (12). 

The white basic selenate, 2Po02Se03, is obtained by treating polonium V) hydroxide or chloride with selenic acid (0.015 iV-5.0 N) the salt is yellow above 250°C and is stable to over 400°C. It is rather less soluble than the basic sulfate, but the solubility increases a hundredfold in passing from 0.05 N to 5 N selenic acid (10), indicating complex ion formation. 

The white basic sulfate, 2Po02-S03, results when polonium(IV) hydroxide or chloride is treated with 0.02 N-0.25 N sulfuric acid. Like the selenate, it is yellow above 250°C and decomposes to the dioxide at 550°C. Solubility studies indicate that it is metastable in contact with 0.1 N-0.5 N sulfuric acid (10). 

This salt is a white crystalline solid made by treating polonium (IV) hydroxide or chloride with dilute acetic acid. Its solubility in the latter increased from 0.2 mg (of Po210)/liter in 0.1 N acid to 82.5 mg/liter in 2 N acid, indicating complex ion formation. The acetato complex is colorless in solution and appears to be more stable than the hexachloro complex (11). 

This is a white crystalline solid obtained by treating polonium(IV) hydroxide or chloride with aqueous oxalic acid solubility studies indicate complex ion formation (11). 

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. 

Evidence for the existence of Po(S04)2 is stronger. The reaction between PoCLt or the hydroxide of polonium with sulfuric acid (0.5-5.0 N) yields a white solid identified as the hydrated solid. The solubility of this material increases with increasing acid concentration, which suggests the formation of anionic sulfate complexes. The white solid loses its water of hydration thermally and leaves a purple solid identified as the anhydrous sulfate. 

A number of other experiments carried out at tracer level concentrations are consistent with the formation of the hydroxide of Po and the polonite ion. Deposits of polonium on gold electrodes are soluble in boiling water and this has been attributed to formation of Po(OH)4. Tracer level °Po can be precipitated from its aqueous solutions in the presence of Bi(OH)3 or Fe(OH)3 carriers with alkali and is presumably carried as the hydroxide. Tracer level °Po dissolves in aqueous alkali and the solubility increases with increasing concentration of hydroxide ion. Also, a neutral species, postulated to be Po(OH)4 was identified by paper chromatography. 

---