ISSN 1070-4272. Russian Journal of Applied Chemistry, 2006, Vol. 79, No. 1, pp. 6 !9. + Pleiades Publishing, Inc., 2006.
Original Russian Text + A.A. Fakeev, 2006, published in Zhurnal Prikladnoi Khimii, 2006, Vol. 79, No. 1, pp. 8!11.
AND INDUSTRIAL INORGANIC CHEMISTRY
Behavior of Manganese(II) in Calcium Formate Solutions
A. A. Fakeev
State Research Institute of Chemicals and Ultrapure Chemical Substances, Moscow, Russia
Received February 9, 2005
Abstract-The solubility in the system Ca(HCOO)
Oat25oC was studied by the isothermal
method. The behavior of manganese in Ca(HCOO)
crystallization from aqueous solutions was examined with
Mn tracer in the concentration range 10
Practical use of high-temperature superconductors
(HTS) is largely determined by the stability of their
properties [1, 2]. Passing from the solid-phase technol-
ogy to synthesis of HTS from aqueous solutions with
the use of metal formates, acetates, and oxalates pro-
vides high chemical homogeneity and stoichiometry
of compositions [3, 4].
Introduction of calcium into HTS based on com-
pounds of bismuth, thallium, rare-earth elements, and
mercury improves the properties of these supercon-
Use of metal formates in production of HTS im-
poses stringent requirements upon the content of im-
purities (iron, manganese, nickel, copper, cobalt,
chromium, etc.), which can strongly affect the micro-
structure, state of grain boundaries, and, in the end,
the electrical and mechanical properties of HTS [6, 7].
Calcium formate of pure grades is not manufac-
tured in Russia.
Calcium formate is fairly well soluble in water and
has a positive temperature coefficient of solubility;
therefore, its crystallization from aqueous solutions
may be one of the simplest and most efficient tech-
niques for synthesis of an ultrapure product.
The efficiency of crystallization as the purificaiton
method can be tentatively evaluated by data obtained
in a study of water3salt systems composed of calcium
formate and ions whose content in HTS is limited.
As the objects of study served water3salt systems
Oat25oC, where M
nickel , copper , lead , magnesium ,
lithium , potassium , zinc , cadmium ,
barium , and yttrium . Systems with lithium,
magnesium, lead, barium, nickel, zinc, and yttrium
ions are of a simple eutonic type, and those with
copper, potassium, and cadmium ions are complex
systems in which double formates are formed. Analy-
sis of the data obtained shows that there is no interac-
tion between the components in the region of crystal-
lization of calcium formate, and ions will be captured
by the forming crystals via adsorption and occlusion
of the mother liquor.
In this study, we examined the behavior of man-
ganese(II) in a wide range of its concentrations in cal-
cium formate solutions at 25oC.
To judge how manganese(II) behaves in crystalliza-
tion of calcium formate from aqueous solutions,
the ranges of macro- and microconcentrations were
Calcium formate and manganese(II) formate dihy-
drate were obtained by the reaction of calcium carbo-
nate of ultrapure 733 grade [TU (Technical Specifica-
tions) 6-09-1990375] or basic manganese carbonate of
analytically pure grade [GOST (State Standard) 72053
77] with formic acid of analytically pure grade
(GOST 5847373). According to the results of chemi-
cal and X-ray phase analyses, the compounds ob-
tained were of composition a-Ca(HCOO)
The content of calcium and manganese jointly
present in the macroconcentration range was deter-
mined by complexometric titration with a 0.05 M
solution of Na
EDTA with Eriochrome Black T as in-
dicator: the sum of calcium and manganese, at pH 12,
and separately manganese, upon precipitation of cal-
cium with a 0.1 M solution of ammonium fluoride.