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本文研究在磷酸中铀的极谱行为,并说明当磷酸浓度小时,U~Ⅴ歧化不完全,可在电极上还原为四价,此时得到两个波,当磷酸浓度增大,U~Ⅴ歧化完全或接近於完全,则仅得一还原波。形成UO~(++)(或UO_2~(++))的络合物,较之增大氢离子浓度对歧化速率影响大。改变温度,对歧化作用影响较小。U~Ⅳ的磷酸溶液在氢波出现前无还原波。经分析波的性质,在稀磷酸中两波均系不可逆波,第一波同时受溶液中化学反应及扩散所控制,随磷酸浓度加大,受扩散控制的影响更显著。由於UO_2~(++)在磷酸中能形成络合物,故K_sη~(1/2)不为常数。本文还提出极谱分析铀的方法,卽利用五价铀歧化完全的还原波,在强酸中可作铀的极谱测定。并建议用磷酸作底液,分析U~Ⅵ或同时测定同一样品中U~Ⅵ及U~Ⅳ含量的方法。
In this paper, we study the polarographic behavior of uranium in phosphoric acid and show that when the concentration of phosphoric acid is small, disproportionation of U ~ Ⅴ is incomplete and can be reduced to tetravalent on the electrode. At this time, two waves are obtained. When the concentration of phosphoric acid increases, Disproportionation is complete or nearly complete, then only one reduction wave. The formation of complexes of UO ~ (++) (or UO_2 ~ (++)) has a greater effect on the disproportionation rate than the increase of hydrogen ion concentration. Changing the temperature has little effect on disproportionation. U ~ Ⅳ phosphoric acid solution before the emergence of hydrogen waves no reduction wave. By analyzing the nature of the wave, the two waves are all irreversible waves in the dilute phosphoric acid. The first wave is controlled by the chemical reaction and diffusion in the solution at the same time. With the increase of the phosphoric acid concentration, the first wave is more significantly affected by the diffusion control. Since UO_2 ~ (++) can form complexes in phosphoric acid, K_sη ~ (1/2) is not constant. This paper also proposed a method of polarographic analysis of uranium, uranium uranium disproportionation using the complete reduction of the wave in the strong acid can be used for uranium polarographic determination. It is suggested that phosphoric acid be used as the bottom liquid to analyze the U ~ Ⅵ or the simultaneous determination of U ~ Ⅵ and U ~ Ⅳ in the same sample.