Mercury niobium fluoride

Niobium pentafluoride forms colourless, highly refractive prisms density 8 2932 at 18° C. It melts at 75 5° C.f and boils at 217° to 220° C. under a pressure of 760 mm. of mercury. It is extremely hygroscopic and deliquesces rapidly in air. It is reduced by hydrogen at 286° C. in contact with platinum to an unstable lower blue fluoride. Excess of concentrated alkali hydroxide or alkali carbonate solutions attack it with formation of the alkali niobate. It dissolves in toluene, paraffin, carbon bisulphide, and other organic solvents. 

Calcium(II), which shows no appreciable complexing, has a distribution coefficient of 147 in 0.5 M perchloric acid and 191 in 0.5 M hydrochloric acid. Strelow. Rethc-meyer, and Bothnia [10] also reported data for nitric and sulfuric acids that showed complexation in some cases. Mercury(II), bismuth(III), cadmium(II), zinc(II), and lead(II) form bromide complexes and are eluted in the order given in 0.1 to 0.6 M hydrobromic acid [11]. Most other metal cations remain on the column. Aluminu-m(III), molybdenum(VI), niobium(V), tin(IV), tantalum(V), uranium(VI), tung-sten(VI), and zirconium(IV) form anionic fluoride complexes and are quickly eluted from a hydrogen-form cation-exchange column with 0.1 to 0.2 M HF [12]. 

Niobium (V) is polarographically reduced to niobium (IV) in slightly acid or neutral solutions of potassium chloride, citrate, oxalate, tartrate, and fluoride at potentials ranging from —1.03 to —2.00 V vs. SCE (179). At large mercury cathodes under controlled-potential conditions, the primary reduction product, niobium (IV),... 

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