Properties of systems Ba(HCOO)2-M(HCOO)2-H 2O (M = Ca or Mg) at 25°C

Article abstract of DOI:10.1023/B:RJAC.0000008288.35845.a4

The systems Ba(HCOO)₂-Ca(HCOO)₂-H₂O and Ba(HCOO)₂-Mg(HCOO)₂-H₂O were studied at 25°C by the solubility method. The effect of the ionic radii of doubly charged metals on the formation of dou

Full text of DOI:10.1023/B:RJAC.0000008288.35845.a4

Russian Journal of Applied Chemistry, Vol. 76, No. 8, 2003, pp. 1221 1224. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 8, 2003,
pp. 1260 1263.
Original Russian Text Copyright
2003 by Vasileva.
PHYSICOCHEMICAL STUDIES
OF SYSTEMS AND PROCESSES
Properties of Systems Ba(HCOO)2 M(HCOO)2 H2O
(M = Ca or Mg) at 25 C
V. Z. Vasileva
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria
Received December 6, 2002
Abstract The systems Ba(HCOO)2 Ca(HCOO)2 H2O and Ba(HCOO)2 Mg(HCOO)2 H2O were studied
at 25 C by the solubility method. The effect of the ionic radii of doubly charged metals on the formation
of double salts containing barium formate was considered.
Barium formate and its binary compounds pos-
sess interesting physical and chemical properties:
Ba(HCOO)2 and BaCd(HCOO)4 2H2O are nonlinear
optical materials [1, 2], Ba2Cu(HCOO)6 H2O is pa-
ramagnetic material [3], and BaY(HCOO)5 4H2O
and Ba2Cu(HCOO)6 4H2O are suitable starting com-
pounds for synthesis of superconductors [4, 5]. A study
of salt systems containing barium formate is of inter-
est because they show promise for practical application.
EXPERIMENTAL
The starting substances were obtained by react-
ing barium, calcium, and magnesium carbonates (all
analytically pure) with a 50% solution of analytical-
ly pure formic acid, followed by recrystallization.
According to chemical, derivatographic, and X-ray
phase analyses, the resulting compounds have the
compositions Ba(HCOO)2 [14], -Ca(HCOO)2 [15],
and Mg(HCOO)2 2H2O [16].
Barium formate is known to form double salts
with formates of some doubly charged metals.
Ba2M(HCOO)6 4H2O (where M is Ni, Co, Cu, or
Zn) (2 : 1 : 4) and BaM(HCOO)4 2H2O (where M
is Cd) (1 : 1 : 2) [6, 7] were obtained by the prepara-
tive method. All these double salts (except that con-
taining cobalt) were separated from the correspond-
ing ternary water salt systems [4, 8 10]. The double
salt Ba2Fe(HCOO)6 4H2O was separated from the
Ba(HCOO)2 Fe(HCOO)2 H2O system at 25 C. It was
established that it is isostructural to the double salts
of the isomorphic series. It is also known that man-
ganese formate does not form a compound with bari-
um formate. The Ba(HCOO)2 Mn(HCOO)2 H2O sys-
tem at 25 C is simple eutonic [11]. It was of interest
to elucidate whether or not barium formate forms
double salts with calcium and magnesium formates.
The solubility was studied by Khlopin’s method
of isothermal elimination of supersaturation [17]:
aqueous solutions of two components of the sys-
tem, taken in various proportions, were prepared at
80 90 C. Then the solution was cooled in a ther-
mostat to the working temperature and vigorously
stirred to constant concentration of a saturated solu-
tion (i.e., to attainment of equilibrium). The tem-
perature was maintained constant to within 0.1 C.
The equilibration time was 15 20 h. After the sus-
pension was filtered, the resulting liquid phase and
the wet solid phase (residue) were analyzed. The Ba2+,
Ca2+, and Mg2+ content in the liquid phases and
residues was determined complexometrically [18]: the
sum of Ba2+ and Ca2+ ions and of Ba2+ and Mg2+
ions was determined by back titration with zinc sul-
fate solution in ammonia solution in the presence of
Eriochrome Black T indicator, Ca2+ was analyzed
at pH 11 (NaOH solution) in the presence of calcone
indicator, Mg2+ was analyzed in ammonia buffer so-
lution after precipitating barium sulfate with a sul-
furic acid solution, and the Ba2+ content was calcu-
lated as the difference between the two determina-
tions. The solid phase composition was determined
To determine the mutual solubility of the compo-
nents and the possibility of formation of new phases
from barium, calcium, and magnesium formates, we
studied the systems Ba(HCOO)2 Ca(HCOO)2 H2O
and Ba(HCOO)2 Mg(HCOO)2 H2O at 25 C. The sys-
tems have not been studied previously. Data on the
solubility of barium, calcium, and magnesium for-
mates were taken from [12, 13].
1070-4272/03/7608-1221 $25.00 2003 MAIK Nauka/Interperiodica

1222
VASILEVA
Table 1. Solubility and solid phase composition in the systems Ba(HCOO)2 M(HCOO)2 H2O (M is Ca or Mg) at 25 C
Liquid phase
Residue, wt %
wt %
Ba(HCOO)2
mol %
Ba(HCOO)2 M(HCOO)2
Ba(HCOO)2 Ca(HCOO)2 H2O system
Solid phase composition
M(HCOO)2
Ba(HCOO)2
M(HCOO)2
23.21
20.59
18.05
16.38
14.93
15.03
15.14
13.25
8.90
2.34
2.09
1.84
1.67
1.54
1.54
1.56
1.33
0.85
0.45
0.28
Ba(HCOO)2
3.25
6.35
8.50
0.58
1.13
1.52
1.92
1.83
1.86
1.76
1.79
1.82
1.98
2.23
71.17
76.13
74.25
70.54
52.06
16.43
70.45
68.75
66.12
73.09
1.55
2.23
3.10
3.50
37.11
70.15
4.30
2.80
1.94
2.10
10.66
10.23
10.38
10.08
10.67
11.29
12.37
14.12
Eutonic
Ca(HCOO)2
4.92
3.02
Ba(HCOO)2 Mg(HCOO)2 H2O system
2.34
23.21
21.11
20.28
18.56
17.45
17.27
14.86
11.45
7.80
Ba(HCOO)2
1.92
3.40
6.11
7.30
7.39
7.55
7.63
8.32
9.80
11.99
2.12
2.05
1.89
1.78
1.76
1.47
1.09
0.72
0.38
0.38
0.68
1.24
1.48
1.5
1.49
1.45
1.53
1.76
2.10
71.33
72.55
81.72
80.12
44.07
4.03
3.25
2.27
1.57
0.80
0.80
1.80
1.37
36.52
59.88
51.79
55.32
60.38
Eutonic
Mg(HCOO)2 H2O
4.20
by Schreinemaker’s method of residues [19] and con-
firmed by chemical, thermal, and X-ray phase ana-
lyses. Thermal analysis was performed on an MOM-12
derivatograph (Hungary), and X-ray phase analysis,
on a DRON-3 diffractometer (CuK radiation, Ni fil-
ter).
Data on the solubility in the Ba(HCOO)2
Mg(HCOO)2 H2O system are presented in Table 1
and Fig. 1b. The solubility isotherm is represented
by the crystallization branches of anhydrous barium
formate [14] and magnesium formate dihydrate [16],
which intersect at the eutonic point of compositions
(wt %): 17.27 Ba(HCOO)2 and 7.39 Mg(HCOO)2.
The components exert the mutual salting-out effect.
For example, the solubility of barium formate in the
system decreases from 23.21 to 17.27 wt %, and that
of manganese formate, from 11.99 to 7.39 wt %.
The results of a study of the system Ba(HCOO)2
Ca(HCOO)2 H2O at 25 C are presented in Table 1,
and the solubility isotherm is plotted in Fig. 1a.
The system is simple eutonic at this temperature.
The crystallizing solid phases are Ba(HCOO)2 [14]
and -Ca(HCOO)2 [15]. The composition of the
eutonic solution is (wt %) 15.03 barium formate and
10.23 calcium formate. As either of the components
is added, the solubility of the other decreases owing
to salting-out.
A study of the two systems showed that neither
double salts nor mixed crystals are formed at 25 C.
Thus, when barium formate is crystallized, the zinc
and magnesium impurities are concentrated in the
mother liquor. Barium formate free of calcium and
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 8 2003

PROPERTIES OF SYSTEMS Ba(HCOO)2 M(HCOO)2 H2O (M = Ca OR Mg) AT 25 C
1223
Fig. 1. Solubility isotherms of the systems (a) Ba(HCOO) Ca(HCOO) H O and (b) Ba(HCOO) Mg(HCOO) H O at 25 C.
2
2
2
2
2
2
magnesium impurities can probably be prepared by
recrystallization.
than 0.75 . These conditions are satisfied by nick-
el(II), cobalt(II), copper(II), zinc(II), and iron(II) ions.
In the systems Ba(HCOO)2 Mg(HCOO)2 H2O (this
study) and Ba(HCOO)2 Mn(HCOO)2 H2O [11] no
double salts are formed. This is because the Mg2+ ra-
dius (0.65 ) is probably too small, whereas the Mn2+
radius (0.80 ) is too large to make this structure
stable. Apparently, the decisive factor influencing
the formation of double compounds of the (2 : 1 : 4)
structural type containing barium formate is the M2+
radius. The double salt of the second type [(1 : 1 : 2)]
(only BaCd(HCOO)4 2H2O is known) crystallizes
from aqueous solution at 25 C with the ionic radius
increasing further. According to the data obtained in
this study, no double salt is formed in the Ba(HCOO)2
Ca(HCOO)2 H2O system. The ionic radii of Cd2+ and
Ca2+ are very close (0.97 and 0.99 , respectively).
All the data presently available for the water formate
systems, including calcium formate, confirm the for-
mation of anhydrous salts [21]. This fact is accounted
for by strong dehydrating action of calcium formate.
Probably, no double salt containing crystallization
water is formed between barium and calcium formates
for this reason.
Table 2 summarizes data on the compositions of
double salts formed in the Ba(HCOO)2 M(HCOO)2
H2O system (where M is Ni, Co, Cu, Zn, Fe, Mn, Cd,
and Ca) at 25 C and lists the M2+ ionic radii [20].
As can be seen, barium formate yields double salts of
stoichiometric composition Ba2M(HCOO)6 4H2O
(2 : 1 : 4) and Ba2M(HCOO)4 2H2O (1 : 1 : 2) with
formates of doubly charged metals. Barium formate
gives the first structural type (2 : 1 : 4) with Ni, Co,
Cu, Zn, and Fe formates. Only the double salt of cop-
per has crystal structure [3]. All these double salts
crystallize in the triclinic system, space group P1,
and have close unit cell parameters, i.e., they are iso-
structural.
The composition of a double salt and the M2+ ion-
ic radius correlate. The structural type (2 : 1 : 4) is
formed at ionic radii larger than 0.69 and smaller
Table 2. Composition of double salts formed in the
Ba(HCOO)2 M(HCOO)2 H2O systems
Ionic
radius,
M2+
Double salt composition
CONCLUSIONS
Mg2+
Ni2+
Co2+
Cu2+
Zn2+
Fe2+
Mn2+
Cd2+
Ca2+
0.65
0.69
0.72
0.72
0.74
0.75
0.80
0.97
0.99
Pure salts
(1) The systems Ba(HCOO)2 M(HCOO)2 H2O
(where M is Ca or Mg) were studied at 25 C and
the formation of pure salts was established.
Ba2Ni(HCOO)6 4H2O [6 8]
Ba2Co(HCOO)6 4H2O [6, 7]
Ba2Cu(HCOO)6 4H2O [4, 6, 7]
Ba2Zn(HCOO)6 4H2O [6, 7, 9]
Ba2Fe(HCOO)6 4H2O
Pure salts [11]
Ba2Cd(HCOO)6 2H2O [6, 7, 10]
Pure salts
(2) Barium formate can be prepared by crystalliza-
tion from an aqueous solution of impurity-free mag-
nesium and calcium salts.
(3) A correlation between the composition of dou-
ble barium salts and the M2+ ionic radius was estab-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 8 2003

1224
VASILEVA
lished. Double salts of the (2 : 1 : 4) type are formed
at the ionic radii within 0.69 0.75 . Above 0.80 ,
another structural type (1 : 1 : 2) is formed.
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Zh. Prikl. Khim., 2000, vol. 73, no. 4, pp. 532 536.
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