1070-4272/01/7404-555 $25.00 C 2001 MAIK [Nauka/Interperiodica]
Russian Journal of Applied Chemistry, Vol. 74, No. 4, 2001, pp. 555!559. Translated from Zhurnal Prikladnoi Khimii, Vol. 74, No. 4, 2001,
Original Russian Text Copyright + 2001 by Lokshin.
AND INDUSTRIAL INORGANIC CHEMISTRY
Manufacture of High-Purity Sodium by Distillation
E. P. Lokshin
Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials,
Kola Scientific Center, Russian Academy of Sciences, Apatity, Murmansk oblast, Russia
Received January 31, 2000; in final form, May 2000
Abstract-The efficiency of purification of technical-grade sodium to remove potassium impurity by distilla-
tion is evaluated theoretically. A technology and apparatus for obtaining high-purity sodium by high-vacuum
distillation were developed. The metal quality was assessed by means of a variety of chemical and physical
High-purity sodium is necessary for precision stud-
ies of its physical properties, synthesis of some spe-
cial-purity compounds of sodium, and manufacture
of high-capacitance tantalum and niobium capacitor
powders [2, 3], photoelectric devices [4, 5], illumi-
nating lamps, high-temperature heat pipes, etc.
A number of methods have been proposed for pu-
rification of sodium, relying upon the difference in
physical and chemical properties between sodium and
impurities contained in it. The methods based on low
solubility of some impurities in the metal being re-
fined (filtration, melting with settling, purification
with cold traps), are suitable for rough purification,
e.g., to remove stock particles or a major part of oxy-
gen [6, 7]. It has been reported  that the content of
Fe, Si, Al, and Cr impurities can be lowered by fil-
tration of sodium heated to 2003500oC from, respec-
tively, 0.003, 0.03, 0.01, and 0.001 wt % to 0.001,
0.001, 0.003, and 0.0001 wt %. These methods failed
to ensure the required degree of purification to remove
poorly soluble impurities and could not separate sol-
uble impurities. Attempts have been made to improve
their efficiency through chemical binding of impuri-
ties into compounds having low solubility .
The chemical binding techniques markedly extended
the number of separable impurities; however, special
reagents and conditions of chemical binding reactions
should be selected for each impurity or group of im-
purities, which complicates practical use of these
A technology for manufacture of [reactor] purity
sodium has been proposed , according to which
the technical-grade metal obtained by electrolysis
is purified by combined application of methods for
oxidative binding of impurities and two-stage filtra-
tion; however, no quality characteristics of the ob-
tained metal have been reported. The characteristics
of the purification methods used for obtaining the
metal make it possible, however, to maintain that
for a number of impurities (potassium, gas impurities,
calcium, iron, etc.) the achieved purification level
was insufficiently high for some fields of application.
Also inefficient were electrochemical [28, 29] and
crystallization  purification techniques.
High-quality sodium can be obtained by reduc-
tion of its special-purity compounds. This technique
is commonly used to produce small amounts of so-
dium directly in photoelectric devices . The most
frequently used salts are chlorides, chromates, and
dichromates, among the commonest reducing agents
are calcium, aluminum, titanium, and zirconium.
The high-temperature processes employed in this
case hinder the development of large-scale apparatus.
The obtained metals require further purification, since
during the purification process the metal vapor carries
away stock particles and gas impurities are evolved,
both of these being absorbed by the condensing metal
. The metal quality decreases dramatically with
increasing scale of the process.
The aim of the present study was to develop
a technology for obtaining high-purity sodium from
the commercially produced technical-grade metal by
the vacuum distillation method.