Pavel Fellner

Electrical conductivity of molten cryolite-based mixtures obtained with a tube-type cell made of pyrolytic boron nitride

AbstractA pyrolytic boron nitride tube-type cell was used to measure the electrical conductivity for molten cryolite, for binary mixtures of cryolite with Al2O3, AlF3, CaF2, KF, Li3AlF6, and MgF2, and for ternary mixtures Na3AlF6-Al2O3-CaF2 (MgF2) and Na3AlF6-AlF3-KF (Li3AlF6). The cell constant was about 40 cm−t. The temperature and concentration dependence of the conductivity in the investigated concentration range was described by the equation

Cathodic overvoltage and the contents of sodium and lithium in molten aluminium during electrolysis of cryolite-based melts

\begin{gathered} \kappa /S cm^{ - 1} = 7.22 exp\left( { - 1204.3/T} \right) - 2.53\left[ {Al_2 O_3 } \right] - 1.66\left[ {AlF_3 } \right] \hfill \\ - 0.76\left[ {CaF_2 } \right] - 0.206\left[ {KF} \right] + 0.97\left[ {Li_3 AlF_6 } \right] - 1.07\left[ {MgF_2 } \right] \hfill \\ - 1.80\left[ {Al_2 O_3 } \right]\left[ {CaF_2 } \right] - 2.59\left[ {Al_2 O_3 } \right]\left[ {MgF_2 } \right] \hfill \\ - 0.942\left[ {AlF_3 } \right]\left[ {Li_3 AlF_6 } \right] \hfill \\ \end{gathered}

Alkali and earth alkaline metal contents in the aluminium cathode in aluminium electrolysis

whereT represents the temperature in Kelvin and the brackets represent the mole fractions of the additions. The standard deviation was found to be 0.026 S cm−1 (∼1 pct). For practical reasons, it is often desired to express composition in weight percent. In that case, it holds that

Determination of sulphur species in solidified cryolite melts

\begin{gathered} \ln \kappa = 1.977 - 0.0200\left[ {Al_2 O_3 } \right] - 0.0131\left[ {AlF_3 } \right] - 0.0060\left[ {CaF_2 } \right] \hfill \\ - 0.0106\left[ {MgF_2 } \right] - 0.0019\left[ {KF} \right] + 0.0121\left[ {LiF} \right] - 1204.3/T \hfill \\ \end{gathered}

Characteristics of Sorel cement prepared from impure materials

whereT represents the temperature in Kelvin and the brackets denote the concentration of the additives in weight percent. However, in this case, the maximum relative error of the conductivity equation can reach up to 2.5 pct.

Determination of the reactivity of CaSO4 · 2H2O

The content of sodium and/or lithium in polarized and nonpolarized aluminium in contact with cryolite melts was determined in a laboratory cell. The cryolite-based melts contained 0 to 20mass% excess AlF3 and 0 to 2.5mass% LiF. The cathodic current density ranged from 0 to 0.5Acm−2. The lithium content in aluminium increases linearly with increasing concentration lithium fluoride in the␣melt. It also increases with increasing cathodic current density and decreasing cryolite ratio. On the other hand the sodium content decreases with increasing concentration of LiF in the melt. This effect is more notable at higher current densities.