Abstract
Information on electric conductivity, transport, melt densities, melt constitution, and vaporization processes in the NaF--AlF/sub 3/ system have been considered in an effort to obtain correlation. The simple picture of cryolite dissociating to sodium and aluminum fluorides and these ionizing to Na/sup +/, Al/ sup 3+/, and F/sup -/ ions is not acceptable. Dissociation to NaF and NaAlF/sub 4/ can be correlated to molten densities, cryoscopic lowering, and vaporization processes. Correlation with electric conductivity and transport data also is obtained if the sodium fluoride further is considered to be dimerized partially in the melt. The best information yields the following values: cryolite composition at 1000 deg C., 65.2% Na/sub 3/AlF/sub 6/, 13.9% NaF, 20.9% NaAlF/sub 4/, by weight; vapor pressures of Na/sub 3/AlF/sub 6/, NaF and NaAlF/sub 4/ in the ratio 5 :l :30; pure, molten NaF is 31% dimerized at 1000 deg C.; equivalent, conductances of Na/sup +/ and F/sup -/ are 83.8 and 58.7, at the cryolite composition. (auth)
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