热分析法测定非计量化合物Na_xWO_3的组成

Thermogravimetric Determination for the Components of Nonstoichiometric Compounds NaxWO3

Na_xWO_3是1种非计量化合物(0<x<1),Na的含量可用化学方法、原子吸收光谱法或离子选择电极法和X射线分析法(0.35<x<1)测定,但上述各法都存在一定问题。一般认为,Na_xWO_3中的W处于W(Ⅴ)和W(Ⅵ)2种不同的价态。常温下,Na_xWO_3在空气中能稳定存在。但实验表明在高温、有氧存在时,它易发生氧化还原反应: 2Na_xWO_3+(x/2)O_2=xNa_2WO_4+(2-x)WO_3显然,反应后样品是增重的,故可用热重法来研究Na_xWO_3的钠含量。

The value of x in sodium tungsten bronzes NaxWO3, a nonstoichio-metric compound, is variable falling in the range 0<x<1. It can be determined by atomic-absorption spectrometry or ion-selective electrodes.The methods have certain disadvantages because the NaxWO3 is chemically inert. The present report relates to a new method for researching components of NaxWO, by thermogravimetry.