Solubility Data Series 75
Nonmetals in Liquid Alkali Metals
Hans Ulrich Borgstedt
and Cezary Guminski
IUPAC-NIST Solubility Data Series. 75.
Journal of Physical and Chemical Reference Data, Vol. 30, No.
4, pp. 835-1158, 2001
Liquid alkali metals have several physical properties which favor
their use in a number of important applications. For example, their
large liquidus temperature range and their excellent heat transfer
properties are important for use as heat transfer media. They are
used in large nuclear reactors in which hundreds of tons of sodium
are circulating, and in small parts of engines for cooling of valves.
Since these metals are among the most electropositive elements, several
of them (Li, Na) can be used in high specific capacity and high energy
density batteries at moderately elevated temperatures. The compatibility
of metallic constructional materials which are used to contain the
liquid metals is strongly influenced by nonmetals present in the liquids.
The physical properties of the liquid metals are also influenced by
dissolved substances. Several nonmetals dissolved in alkali metals
are able to form ternary compounds with components of the constructional
materials. Thus, corrosion and compatibility studies have been accompanied
by extensive chemical work related to the solutions of non-metallic
substances in liquid alkali metals. All available solubility data
of nonmetallic elements and some of their compounds in the five liquid
alkali metal solvents (Li, Na, K, Rb, and Cs) are collected and compiled.
Original publications with reliable data and information on the methods
used to generate them are reported in individual Compilations. When
numerical data are not given in a publication, the data are often
read out from figures and converted into numerical data by the compilers.
The precision of this procedure is indicated in the Compilations under
Estimated Error. Evaluated solubility data are tabulated at the end
of the Critical Evaluations: if there is agreement of at least two
independent studies within the experimental error, the solubility
values are assigned to the "recommended" category. Values are assigned
as "tentative," if only one reliable result was reported, or if the
mean value of two or more reliable studies was outside the error limits.
In the tabulation, three, two, or one significant figures are assigned
for respective precisions that are better than ±1% and ±10% and worse
than ±10%. If necessary, the solubilities are recalculated into mol
%. The completeness of this investigation of the literature has been
confirmed and extended by studying several reviews dealing with the
solution chemistry of substances in the alkali metals. Solubility
data are sometimes measured under parameters, which are not standard
conditions of such measurements. Frequently measurements are performed
under constrained pressure. The solubility of noble gases or other
gases, which do not form compounds with the alkali metals, depends
on the gas pressures. This dependency is documented in the data sheets.
Schematic phase diagrams are presented in systems for which they assist
the understanding of the data and the conclusions. They are based
on the most recent state of knowledge and generally presented in the
Critical Evaluations. Some solubility diagrams are shown in form of
a log solubility versus reciprocal temperature function. These figures
illustrate the larger scatter of data for systems in which interfering
reactions cause unstable behavior of solutions. While several solutes
are well defined substances, other systems need still additional studies
to define the equilibrium solid state compound. One should realize
that estimations of the stoichiometry and thermal stability of ternary
compounds are experimentally difficult, and their results are often
©2001 American Institute of Physics.
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