Freezing Points and Vapor Pressures of the System Potassium Fluoride—Hydrogen Fluoride<sup>1</sup>

Cady, George H.

doi:10.1021/ja01322a001

Cited by 76 publications

(47 citation statements)

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“…Their heating leads first to the polymorphous transformation of the tetragonal modification into the cubic one (first endothermic peak), and then to melting without appreciable decomposition (second endothermic peak). The temperatures of these endothermic peaks are in good agreement with literature data for the temperatures of the polymorphous transformation [19] and melting of these compounds [4,[20][21][22]. Further temperature increase leads to their decomposition, so that the removal of hydrogen fluoride occurs in this case from the melt, and the corresponding endothermic peaks are of a complex form.…”

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confidence: 88%

Thermal stability of alkali metal bifluorides

Opalovsky

Fedorov

Fedotova

1970

Journal of Thermal Analysis

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The thermal stability and non-isothermal kinetics of the decomposition of alkali metal bifluorides were studied using a derivatograph. The removal of hydrogen fluoride from LiF. HF and NaF 9 HF takes place before melting and their decomposition occurs in a single stage; however, potassium, rubidium and cesium bifluorides at first undergo polymorphous transformation and melting on heating, and their decomposition proceeds stepwise. The thermal stability of alkali metal bifluorides has been found to increase with increasing ionic radius of the cation, reflecting its correlation with the hydrogen bond strength in these compounds.Of the presently known hydrofluorides the alkali metal bifluorides MF 9 HF (MHF~) are the most stable thermally. The thermal stability of these compounds is important from the point of view of their practical application. However, the literature data on this point are sometimes contradictory. The variety of methods used by the authors of the works mentioned above makes the comparison of the results difficult as they often differ greatly. The insufficient purity of the studied substances, especially in the early works, also gave rise to inaccuracies. The kinetics of the decomposition of bifluorides has not been studied at all. In the present work the thermal stability and non-isothermal kinetics of the decomposition of alkali metal bifluorides were studied by thermogravimetry.Lithium bifluoride was obtained by crystallization from a saturated solution of lithium fluoride (analytical grade) in hydrofuoric acid of special purity [3]. The crystals obtained were washed several times with anhydrous hydrogen fluoride to remove water, and then excess HF was exhausted in a vacuum desiccator 1" 3., Thermal AnaL 2, 1970

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supporting

confidence: 88%

Thermal stability of alkali metal bifluorides

Opalovsky

Fedorov

Fedotova

1970

Journal of Thermal Analysis

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“…Later, more exact data for alkali metal and ammonium hydrofluorides were obtained by studying the melt diagrams of the systems HF -MF [6][7][8][9][10][11]. Experimental data indicate that of the above hydrofluorides only NaF.…”

mentioning

confidence: 99%

“…Addition of lithium and sodium fluorides to potassium hydro fluorides markedly decreases their melting points, irrespective of the slight solubility of LiF and NaF in these melts [7,15]. The S-shape of the density and viscosity isotherms of the system HF -KF is retained when LiF, NaF, RbF and CsF are added [16,17].…”

mentioning

confidence: 99%

“…The vapour pressure in the system HF-KF has been measured by Cady [7] who constructed isobars for 50, 100 and 250 torr. Later, the vapour pressure above melted HF-KF was studied in the area of KF " 2HF formation within the temperature range 70-110 ~ [37].…”

mentioning

confidence: 99%

“…Later, the vapour pressure above melted HF-KF was studied in the area of KF " 2HF formation within the temperature range 70-110 ~ [37]. Data on the system HF-KF [7] have been further utilized to establish the dependence of HF vapour pressure on the composition of the melt (from KF to KF 9 4HF) at temperatures of 298-550 K [12].…”

mentioning

confidence: 99%

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