摘要
在常温常压下,从近中性的混合铈、镨硝酸盐水溶液中,采用臭氧(或氧气)氧化,制得了红棕色的四价铈镨杂多核氧化物,这种在铈的存在下镨的氧化,拟称为“带同氧化”。通过化学分析,X射线衍射物相分析以及与二氧化锰作用的研究,证明了杂多核氧化物中四价镨的存在。该杂多核氧化物溶于浓硝酸、浓盐酸和冰醋酸中,生成血红色的溶液。通过颜色的变化和紫外可见光谱的研究,考察了四价镨在这些溶液中的稳定性。四价镨在冰醋酸中相当稳定,浓硝酸中一小时内逐渐消失,浓盐酸和硫酸(1:1)中则极不稳定。含四价镨的浓硝酸和冰醋酸溶液的吸收光谱,分别在460nm和440nm处呈现宽带特征吸收峰。通过与不含四价镨的纯铈(Ⅳ)、纯错(Ⅲ)及铈钕混合氧化物等光谱的比较,初步认为这两个特征吸收峰与四价镨的存在有关。
Although quite a number of tetravalent praseodymium compounds have been prepared and well characterized,the solution chemistry of tetravalent praseodymium is little known.By means of"Carrier oxidation"through cerium from a 4:1 mixture of Ce(Ⅲ)and Pr(Ⅲ)nitrate in aqueous solution,using ozone as oxidizing agent at room temperature and at pH around 6.5,a more reactive heteropolynuclear oxide hydrate with chocolate brown color was obtained.After drying in vacuo at a temperature not higher than 50℃,chemical analysis and X-ray diffraction pattern(Fig,1,2).confirmed the formation of PrO_(2)in the mixed oxide.The degree of readiness for that heteropolynuclear oxide to get into solution differs markedly in con.HC1,con.HNO3 and glacial acetic acid.The stability in those solutions also appearsdifferent.In con.HC1,solution formation is very easy;the blood red color due to Pr(Ⅳ)lasts for only a few minutes.Solution formation in con.HNO_(3)is less easy,but the blood red color lasts much longer.In nitric acid solution,oxidation of MnO_(2)·H_(2)O to MnO_(4)^(-)has been observed visually;transient formation of H_(2)O_(2)has been revealed in recording spectrophotometer(Fig.4,7).These phenomena substantiate the relative values of their respective electrode potentials given in literature.Solution of Ce(Ⅳ)-Pr(Ⅳ)heteropolynuclear oxide into glacial acetic acid needs brief warming;the blood red color can persist for a long time.Mixed complex compounds containing Ce(Ⅳ)and Pr(Ⅳ)can be obtained from that solution by precipitation with appropriate reagents.By means of recording spectrophotometer,and with the use of Ce(Ⅳ)as reference solutions,absorption bands with highest absorption at 460nm(Fig.3)and 440nm(Fig.10)have been observed in nitric acid and in glacial acetic acid solutions respectively.Those absorption bands are considered to be characteristic of Pr(Ⅳ)compounds.Preliminary experiment reveals that Tb can likewise form Ce(Ⅳ)-Tb(Ⅳ)hetero-polynuclear oxide.Its solution chemistry is quite similar to that of P
作者
顾翼东
宋沅
Gu Yidong(Ku Yih-tong);Song Yuan(Department of Chemistry,Fudan University)
出处
《高等学校化学学报》
SCIE
EI
CAS
1980年第2期1-13,共13页
Chemical Journal of Chinese Universities
