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ORNL-2106 - the Molten Salt Energy Technologies Web Site

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ANP PROJECT PROGRESS REPORT<br />

liquidus temperatures was noted in attempts to<br />

determine <strong>the</strong> melting point of pure ZnF,. Cooling<br />

curves showed liquidus effects ranging from<br />

885 to 94OoC and a second break at or near 845OC.<br />

Since ZnO was found in all <strong>the</strong> samples that<br />

were examined subsequent to <strong>the</strong> melting-point<br />

determinations, it seemed probable that <strong>the</strong><br />

liquidus temperature was affected by <strong>the</strong> amount<br />

of ZnO present. Confirmation of this postulate<br />

was obtained when a cooling curve obtained with<br />

oxide-free ZnF,, prepared by NH,F.HF treatment<br />

of ZnF, previously dried in an HF atmosphere,<br />

showed a <strong>the</strong>rmal effect only at 940 f 5OC. Be-<br />

cause of <strong>the</strong> large discrepancies between this<br />

value for <strong>the</strong> melting point of ZnF, and those<br />

reported in <strong>the</strong> literature (872OC by Puschin and<br />

Ba~kow,,~ and 875 f 3OC by Haendler, Patterson,<br />

23N. Puschin and A. Baskow, Z. anorg. Cbem. 81,<br />

359 (1913).<br />

92<br />

and Bernard2,), <strong>the</strong> slowly cooled ZnF, was<br />

analyzed chemically and spectrographically. It a<br />

was also carefully examined petrographically and<br />

by x-ray diffraction, along with a highly precise<br />

determination of cell parameters. Since no 3<br />

evidence was found of <strong>the</strong> presence of impurities<br />

in more than trace amounts, <strong>the</strong> melting points for<br />

ZnF, reported in <strong>the</strong> literature are believed to be<br />

erroneous, possibly because of oxide contamination,<br />

Thermal analysis data obtained with<br />

mixtures formed by adding 5, 10, 15, and 20 mole %<br />

ZnO to purified ZnF<br />

which melts ai 850 f 5<br />

show that <strong>the</strong> eutectic<br />

20 C contains approximately<br />

21.5 mole % ZnO. Only <strong>the</strong> pure components were<br />

found in <strong>the</strong> slowly cooled mixtures, and thus it<br />

appears that solid solutions do not occur, at least<br />

at room temperature.<br />

*,He M. Haandlar, W. L. Patterson, Jr,, and W. Je<br />

Bernard, I. Am. Chem. SOC. 74, 3167 (1952).

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