For producing fluorescent-grade low-Cl-Eu2O3, research was made on the ef fects of oxalic acid precipitation conditions (temperature, feeding method etc.) and treat ment methods of the precipitated products on Cl-content in Eu2O3. Optimum technological conditions for production of low-Cl-Eu2O3 have been found.

Nd2O3 is obtained from NdFeB scraps by H2SO4-double salt process.Laborato ry-scale test shows the process is stable and practicable (purity of obtained Nd2O3＞95%,re covery＞85%,other techno-economic data are quite satisfactory), and worthy to be popular ized.

The relation between crystalline RE Carbonates precipitated from various types of leaching liquor of weathered leach-deposited RE ore and its RE composition has been studied by chemical analysis, XRD,IR spectrograph,SEM,TGA and DTA, The results are as follows: The quality of crystalline RE carbonates is better than one of RE oxalates.Crys talline RE carbonates are simple crystallo-hydrates of RE carbonates.The type of crystalline RE carbonates varies with the composition of RE carbonates.

The basic thermodynamic conditions of the process on producing ytterbium metal from the enriched oxides of Thulium,Ytterbium and Lutecium by La-reduction and Ce reduction have been calculated and reduction experiments were successfully carried out. The experiment results showed that under proper technical conditions, the ytterbium metal of more than 98% purity could be obtained in laboratory with direct recovery of 85%～90%.In this paper, behaviour of main rare earths components and other impurities during the reduc tion and their distribution in products have been investigated. Application comparison between La-reduction and Ce-reduction was breifly made.

The paper briefly describes the bench scale test and 3 000 A electrolyzer pro duction of Pr metal by electrolysis of Pr oxide. The influence of electrolyte composition,electrolysis temperature, cathode current density and feedrate on the production efficiency is discussed. The practice shows that the electrolyzer has worked continuously and stably on a self-heating basis.The daily output of Pr metal per electrolyzer reached 65～70kg,metal re covery 90%,current efficiency＞80%.

Study is made of KaTaF7 redissolution to reveal the technological conditions and impurity removal efficiency,etc.The industrial application of the said process is de scribed.

Study is made on the design of multi-tower Series-operating system for tower extractor.The results show that the recommended systems feature simple process, easy op eration and stable performance.

Basic requirements for the quality of hard metals metallographic specimen are introduced. The problems of the existing preparation method for the said specimen are ana lyzed, some modification and research are made.The author thinks it quite necessary to work at the research, experince exchange, technical demonstration and populatrization of achievement of advanced specimen preparation methods.

The paper describes the improvement of 4-tube reduction furnace for W pow der and its production practice results show that the temperature in improved furnace is more uniform with less energy consumption.

According to low output of Ta and Nb ore concentrate and short supply of raw materials for metallurgy in China, the countermeasures are presented.