Analytical Chemistry of Niobium and Tantalum. Critical Analysis of Existing Methods

Abstract

Table VI. Silicon Determination in Calcium Oxide" with and without Fluoride Treatment (7 silicon per 100 ml.) With Without Fluoride & Fluoride 137 98 138 96 136 96 136 91 137 95" A 1-gram sample was dissolved in dilute hydrochloric acid, transferred 100-ml. volumetric flask, and made to volume. Solution was filtered and 2-ml. aliquots were removed for analysis.b The 2-ml. aliquots were diluted with water, treated with 0.5 ml. of zirconium-fluoride solution, and warmed for 0.5 hour.The effect oí fluoride treatment is vividly illustrated in Table VI. The results show that a filtered solution may contain unreactive silicon. Conventional recovery experiments may not indicate this type of interference and consequent lack of accuracy.The problem oí loss of silanes during solution of calcium metal was not investigated. It has been reported ( 7) that slow addition of the metal to dilute sodium hydroxide minimizes the loss of silicon, provided the solutions are kept cool.Metal. Dissolve a 1-gram sample of metal by slowly adding the fine chips to a Fluorethene beaker containing 15 ml. of about 0.35 M sodium hydroxide. The solution should not be permitted to become warm. After all the metal has been added, acidify the solution by the addition of dilute hydrochloric acid. Add 0.5 ml. of the zirconium-fluoride solution and warm for 0.5 hour at low heat on the hot plate. Complete the analysis, using the recommended procedure.

Refractory metals and nickel in high temperature chlorine‐containing environments ‐ thermodynamic prediction of volatile corrosion products and surface reaction mechanisms: a review

“…Here the difference between nickel and the refractory metals is obvious: Nickel can bind to only two chlorine atoms at most . The refractory metals on the other hand need to form much higher coordinated compounds, up to hepta‐ (NbCl 5 , TaCl 5 , MoCl 5 , WCl 5 ) and hexachlorides (WCl 6 ), in order to become stable enough to disengage from the surface .…”

Geochemical association of niobium (columbium) and titanium and its geological and economic significance

“…This process involves the chlorination of titanium-rich ore to form TiC14. Since TiC14 boils at 136°C and NbC15 at 243°C, conditions are favorable for obtaining good separations, as recently demonstrated Atkinson, Steigman, and Hiskey (1952). Further research on the process is obviously needed, as well as a study of the economic factors.…”

Quantitative Analysis of Niobium and Tantalum in Ores by Fluorescent X-Ray Spectroscopy

“…Berry et al (1) used sucrose as an example of a compound which caused large errors because of viscosity. Bills et al (2) showed that the presence of 5000 p.p.m. of glycerol with 5 p.p.m.…”