Trivalent uranium solution studies

Neptunium, like uranium, can occur in aqueous solution in four oxidation states trivalent, tetravalent, pentavalent and hexavalent. The most studies have been conducted on the hydrolysis and solubility of neptunium(V) species and phases. There are much fewer studies on the hydrolysis and solubility of neptu-nium(IV). Not many studies are available that have determined the solubility or stability constants of neptuniumfVI). However, it is clear from the studies that have been undertaken that the hydrolytic behaviour of neptunium(VI) is quite similar to that of uraniumfVI). There is only a single study that has determined stability constants for the hydrolytic species of neptunium(III). 

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