Competition of hydrolysis and complex formation in the Cu(NO 3)2, (H+)-NH3·H 2O-H2O system

Article abstract of DOI:10.1023/A:1020739624177

The concentration regions of prevalence of various chemical interactions in the Cu(NO₃)₂, (H⁺)-NH ₃·H₉O-H₂O system were determined by dilatometry, pH-metry, and electronic spectroscopy of s

Full text of DOI:10.1023/A:1020739624177

Russian Journal of Applied Chemistry, Vol. 75, No. 7, 2002, pp. 1055 1060. Translated from Zhurnal Prikladnoi Khimii, Vol. 75, No. 7,
002, pp. 1072 1077.
Original Russian Text Copyright
2
2002 by Burkov, Sidorov, Sal’nikov, Kryuchkova.
INORGANIC SYNTHESIS
AND INDUSTRIAL INORGANIC CHEMISTRY
Competition of Hydrolysis and Complex Formation
+
in the Cu(NO ) , (H ) NH H O H O System
3
2
3
2
2
K. A. Burkov, Yu. V. Sidorov, Yu. I. Sal’nikov, and N. A. Kryuchkova
St. Petersburg State University, St. Petersburg, Russia
Kazan State University, Kazan, Tatarstan, Russia
Received November 15, 2001
Abstract The concentration regions of prevalence of various chemical interactions in the Cu(NO ) ,
3
2
+
(
H ) NH3 H O H O system were determined by dilatometry, pH-metry, and electronic spectroscopy of
2 2
solutions and by X-ray phase and gravimetric analyses of precipitates. The adequacy of the model proposed
was confirmed by CPESSP calculations.
Occurrence of equilibria (1) in aqueous ammonia
solutions suggests that either ammine complexes
or mono- and polynuclear hydroxo complexes, and
probably mixed hydroxo ammine complexes can be
formed in systems metal ion ammonia water:
electrolyte. It was shown that, along with the dominat-
2+
+
ing binuclear complex Cu (OH) , the CuOH and
2
2
3+
Cu (OH)
species are formed in solution. Their
2
hydrolysis constants logK , equal to 10.93 0.02,
h
7.4 0.1, and 6.02 0.02, respectively, were deter-
mined, and the stability constants log were cal-
+
NH3 + H O = NH H O = NH + OH .
(1)
culated in view of pK = 14.09 found in [3]: 6.69
2
3
2
4
w
+
+
2+
for CuOH , 17.25 for Cu (OH) , and 8.07 for
2
2
3
The hydrolysis and complex formation can compete.
Such reactions, which often take place in heterogene- clear species Cu (OH) . The most probable hy-
Cu (OH) . Several authors also detected the trinu-
2
2
+
3
4
ous systems, result in the precipitation of poorly
soluble compounds and, in certain cases, in their sub-
sequent dissolution.
droxo compounds in the solid state are copper hy-
droxide Cu(OH)2 and also the binuclear complex
Cu (OH) NO characteristic of nitrate systems [4].
2
3
3
In solutions of copper ammines, there are only
It is often difficult to gain insight into the chemical
interactions and state of the components in such com-
plicated systems consisting of both solutions and
solids. The subject of this work was the Cu(NO ) ,
2+
mononuclear complexes [Cu(NH ) ] , n = 1 4
3 n
(
however, there are also scarce data on the complexes
with n 5 and 6). Their step stability constants were
determined by many authors [1]. For example, the fol-
3
2
+
(
H ) NH H O H O system. The experimental data
3 2 2
lowing values are given in [5]: logk = 4.31, logk =
were obtained dilatometrically. This method allows
highly accurate monitoring of changes in the solution
volume due to chemical interactions. Also, we used
potentiometric titration and electronic absorption spec-
troscopy of solutions (after thorough filtration to re-
move precipitates, which, in turn, were studied by
chemical and X-ray phase analyses). The data of the
dilatometric titration were treated with a simulating
CPESSP program.
1
2
4
3
1
.67, logk = 3.04, and logk = 2.30 (thus, log
=
3
4
3.32 at 18 C in a 2 N solution of ammonium nitrate).
Attempts were made to gain insight into processes
occurring under the action of aqueous ammonia solu-
tion on the suspension of copper oxide CuO. Gubeli
et al. [6], when fitting the CuO solubility curve, sug-
gested the presence of a number of species in the sys-
2
+
2 n
2+
tem: Cu , Cu(OH)
(n = 2 4), Cu(NH ) (n =
n
3 n
+
+
2
4), and also Cu(NH )(OH) , Cu(NH ) (OH) , and
Hydrolysis and complex formation of copper(II)
with ammonia were extensively studied as separate
processes. The hydrolysis of copper(II) ions was
studied previously in [1] by potentiometric titration
with an alkali (NaOH) at a constant ionic strength,
3 3 3
Cu(NH ) (OH) . At the same time, this conclusion
3 2
2
seems doubtful, because the well-known existence of
binuclear hydroxo complexes was not included in the
model.
and also in [2], with 3.0 M NaClO as supporting
Comparison of the published data shows that vari-
4
1
070-4272/02/7507-1055$27.00 2002 MAIK Nauka/Interperiodica

1056
BURKOV et al.
copper ions, N = [NH H O]/[Cu ] for Fig. 1 and
2+
3
2
3
1
V , cm mol
2+
m
N = [NaOH]/[Cu ] for Fig. 2.
For more convenient comparison and interpreta-
tion, we accepted the starting point of the hydrolysis
of Cu2 ions (i.e., point B) as the point of zero value
of N . Thus, the values N < 0 in the beginning of the
curve (straight line AB) corresponded to the titration
region in which the main component [copper(II) ions]
yet do not enter into the reaction, and the possible
scatter of the starting points A in various titration
experiments may be due to different amounts of the
acid added.
+
The dilatometric titration curves for such com-
plicated systems as the system under study consist of
a number of linear portions, each of which corre-
sponds to various chemical reactions. We have shown
earlier [7 9] that the singular points (according to
Mendeleev’s definition [10]) in the composition
property diagrams correspond to the boundaries of
the regions with prevalence of particular types of reac-
tions, depending on N. Thus, the change in the solu-
tion molar volume Vm for each particular reaction
Fig. 1. Curves of (I) dilatometric and (II) potentiometric
+
titration for the system Cu(NO ) , (H ) NH H O H O.
3
2
3
2
2
Concentrations, M: copper(II) nitrate 0.091 and ammonia
0
(
.312; ionic strength of solutions
1 M (NaNO ).
3
V ) Change in molar volume and (N) the number of
m
NH H O moles per mole of Cu(II); the same for Figs. 3
and 5.
3
2
is determined as the slope of the V = f(N) depen-
m
3
1
dence in the dilatometric curve portion under con-
sideration.
V , cm mol
m
A detailed study of the dilatometric titration data
+
for the system Cu(NO ) , (H ) NH H O H O
3
2
3
2
2
(
Fig. 1) in comparison with the data on bulk proper-
+
ties of the system Cu(NO ) , (H ) NaOH H O
3
2
2
(Fig. 2), and also with the data of other methods,
allowed us to reveal and interpret the regions of pre-
valence of the following chemical reactions.
Fig. 2. Dilatometric titration curve for the system
(1) The neutralization of excess nitric acid, which
is usually added to the initial solution to prevent the
spontaneous hydrolysis of copper(II). The region of
the neutralization corresponds to the linear portion AB
in the dilatometric curves shown in Figs. 1 and 2.
A set of facts indicate that specifically neutralization
takes place in both systems within boundaries of the
AB portion. First, point B coincides with the calcu-
lated equivalence point with respect to the acid. Sec-
ond, the first equivalence point in the pH-metric curve
corresponds to point B. Furthermore, after this point,
hydroxo compounds start to precipitate.
+
2+
Cu(NO ) , (H ) NaOH H O. Concentrations, M: Cu
3
2
2
ions 0.228, NaOH 0.330; ionic strength of solutions 1 M
(
NaNO ). ( V ) Change in the molar volume; N =
3 m
2
+
[NaOH]/[Cu ].
ous chemical reactions can compete in the system
+
Cu(NO ) , (H ) NH H O H O.
3
2
3
2
2
The results of dilatometric and potentiometric titra-
tion of copper nitrate solution (with addition of HNO3
to prevent spontaneous hydrolysis) by an ammonia
solution are shown in Fig. 1. The dilatometric curve
corresponding to the titration in the system Cu(NO ) ,
3
2
+
(
H ) NaOH H O, i.e., to the hydrolysis of copper(II)
There is principle difference between the courses of
volume changes in neutralization with sodium hydrox-
ide and ammonia aqueous solutions. Reaction (2) in-
volving a strong base and a strong acid (Fig. 2, por-
tion AB) is accompanied by an increase in volume
2
ions without complex formation, is shown in Fig. 2.
The dilatometric curves were constructed as the plots
3
1
of changes in the molar volume V (cm mol ) vs.
m
the number of added moles of a base N per mole of
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 7 2002

COMPETITION OF HYDROLYSIS AND COMPLEX FORMATION
1
1057
3
(
VAB = 21.06 cm mol ):
,
% of total Cu content
NaOH + HNO3 = H O + NaNO .
(2)
2
3
The observed positive volume effect agrees well
with the published data [9]. The main component of
VAB is the partial molar volume of the forming water
3
1
(
V = 18.07 cm mol at 25 C). An additional con-
w
tribution to the volume effect is due to the dehydra-
+
tion of H and OH ions and, correspondingly, to
their deelectrostriction [11]. Reaction (2) can be
written in the ionic form as follows:
Fig. 3. Plot of the precipitate yield
(2) 1.0, (3) 1.5, (4) 2.3, (5) 3.1, and (6) 4.0; the same for
vs. N. N: (1) 0.5,
+
OHaq + H = H O + aq + VAB
,
(3)
aq
2
Fig. 4.
where aq is water in the hydration spheres of ions.
both cases corresponded to N = 1.5 mol. The volume
With aqueous ammonia solution (Fig. 1), the pat-
tern of volume changes in the AB section is opposite,
i.e., the volume of the system decreases. The VAB
value for reaction (4) [or (5) in the ionic form] is
3
1
changes describing the BC section are (cm mol )
VBC (NaOH) = 31.44 and VBC (NH H O) = 6.04.
3
2
As found previously for induced hydrolysis of iron(III)
ions [8], the hydrolytic polymerization under the ac-
tion of a strong base is accompanied by an additional
positive volume effect, as compared to the first sec-
tion corresponding to the neutralization of an acid. For
the systems under consideration, these additional con-
3
1
4
.85 cm mol :
NH3 H O + HNO = H O + NH NO ,
(4)
(5)
2
3
2
4
3
NH3(aq) + H+
(aq)
= NH+
.
4(aq)
3
1
tributions are as follows (cm mol ): VBC (NaOH)
VAB(NaOH) = 31.44 21.06 = 10.38 for NaOH
titrant and VBC (NH H O) V (NH H O) =
At first glance, such a difference in the volume effects
as compared to the neutralization with alkali) seems
3
2
AB
3
2
(
6
.04 ( 4.85) = 10.89 for NH H O titrant. This fact
3 2
strange, as in both cases water molecules are formed,
and dehydration of the acid protons also makes a
certain positive contribution. The observed effect is
due to specific features of the neutralization with
aqueous ammonia (namely, the partial molar volume
of the initial ammonia in solution is larger than the
partial molar volume of an aquated ammonium ion
formed in the reaction [12, 13]).
allows an important conclusion that, in spite of
different nature of the bases in the two titration
experiments, the volume effect resulting from the hy-
drolysis and hydrolytic polymerization remains the
same.
According to X-ray phase analysis, the solid phase
is the same in both cases: the known binuclear copper
trihydroxonitrate Cu (OH) NO . No ammine and
2
3
3
To confirm additionally the fact that acid is neu-
tralized in the initial stage of the titration (por-
tion AB), we titrated a non-acidified solution of cop-
per(II) nitrate with an ammonia solution [the system
Cu(NO ) NH H O H O]. As expected, the result-
mixed hydroxo ammine complexes were detected in
the solid phase.
The B C portion of the plot of the precipitate
weight (% of total copper content) vs. N in Fig. 3 (in
the B C portion, precipitates were isolated at N 0.5,
3
2
3
2
2
ing titration curve was similar to the curve under
1.0, and 1.5) is a straight line ascending in parallel to
consideration, except for the AB portion.
the BC portion of the dilatometric curve (Fig. 1). The
amount of the precipitate linearly increased, reaching
a maximum at N = 1.5, i.e., in point C . The electronic
absorption spectra (Fig. 4) show that the solutions
(2) After passing point B, a blue precipitate is
formed in both systems under consideration, which is
accompanied by an increase in volume, suggesting
occurrence of a new chemical reaction (Figs. 1 and 2, corresponding to the straight-line portion BC of the
straight line BC) responsible for a sharp change in
the molar volume. Point B is the starting point for
measuring the amount N (mol) of a titrant [sodium
hydroxide (Fig. 2) or ammonia (Fig. 1)] reacting di-
rectly with copper(II). The length of the BC section in
dilatometric curve contain no Cu(II) ammine com-
plexes (the solutions were prepared by thorough filtra-
tion at the same N values as the precipitates). The
absorption band in the region 600 625 nm, character-
istic for copper ammines [14], was absent from the
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 7 2002

1058
BURKOV et al.
+
(
H ) NH H O H O (Fig. 1, curve II) in the region
3
2
2
corresponding to the BC portion reveales a slight
increase in pH at N from 0 to 1.5. The sharp pH in-
crease in the second equivalence point at N = 1.5
coincided with singular point C in the dilatometric
curve. At N > 1.5, the pH changed only slightly.
Hence, the formation of hydroxo species, with binding
of hydroxide ions without noticeable pH change, was
complete.
(
3) Analysis of the VCD(NaOH) and VCD(NH3
H O) values in the CD portion (Figs. 1, 2) revealed
2
,
nm
principal differences in the nature of volume changes
and, hence, in chemical reactions in the two systems
under consideration (i.e., when sodium hydroxide or
aqueous ammonia solution was added). When titrating
with sodium hydroxide (Fig. 2), the volume continued
to grow up to N = 2, with only the value of the volume
effect changed [ VCD(NaOH) = 13.56 cm mol ].
The transformations in the system were associated
with further hydrolytic reactions whose final solid
product was a mixture of copper hydroxide and oxide
Fig. 4. Electronic absorption spectra of solutions obtained
in the system Cu(NO ) NH H O H O at various
N values. (D) Optical density and ( ) wavelength.
3
2
3
2
2
spectra of solutions corresponding to N 0.5, 1.0, and
.5 (curves 1, 2, and 3, respectively). At the same
time, a decrease in the intensity of the absorption band
in the region of 800 nm, characteristic for copper(II)
aqua complexes [15], was indicative of gradual de-
crease in the copper amount in the solution. At N =
1
3
1
2+
formed by partial decomposition of Cu(OH) (which
1
.5 (singular point C), Cu ions were almost absent
2
was also confirmed by X-ray phase analysis). The CD
portion is located between N 1.5 and 2, which ap-
parently corresponds to reaction (8) and parallel par-
tial decomposition (9) of copper hydroxide into cop-
per oxide and water (in the course of the experiment,
the precipitate gradually darkens owing to the forma-
tion of black copper oxide):
from the solution. Thus, in the range of N from 0 up
+
to 1.5 in the system Cu(NO ) , (H ) NH H O H O,
3
2
3
2
2
the hydrolysis (i.e., interactions also characteristic of
the induced hydrolysis under the action of a strong
base) prevailed over the formation of ammine com-
plexes.
The following reactions are presumably responsible
for the volume changes in the BC portions of the dila-
tometric curves for both systems under consideration:
Cu (OH) NO + OH = 2Cu(OH)2 + NO3,
(8)
(9)
2
3
3
Cu(OH)2 = CuO + H O.
2
2
Cu2+ + NO3 + 3OH = Cu (OH) NO ,
(6)
2
3
3
The volume changes are virtually complete in sin-
gular point D (N = 2) owing to the completion of
main chemical reactions in the system: after N = 2,
the titration curve (Fig. 2) flattens out.
+
2
Cu2+ + NO + 3NH H O = Cu (OH) NO + 3NH . (7)
3 3 2 2 3 3 4
Apparently, the hydrolytic transformations de-
scribed by Eqs. (6) and (7) involve the stages of the
formation of copper mono- and polynuclear hydroxo
At the same time, in titration with aqueous am-
+
3+
2+
monia (Fig. 1), the volume decreased [ VCD(NH3
complexes CuOH , Cu OH , and Cu (OH) , which
2
2
2
3
1
H O) = 2.93 cm mol ], which continued up to
N = 4.
2
are precursors of the forming solid phase.
It was shown in [8] that the positive volume effect
is due to liberation of water molecules from the hydra-
tion shells of the interacting ions upon the hydrolytic
polymerization (the molar volume of water in the free
state is 18.07 cm mol , and in hydration shells
of double-charged cations of 3d metals it is about
+
In the Cu(NO ) , (H ) NH H O H O system,
3
2
3
2
2
the CD section gives one more evidence of competi-
tion between the chemical reactions. In contrast to
the previous example (titration with alkali), the further
titration with ammonia results in the dissolution of
the copper hydroxo complex and in its conversion to
copper(II) ammines:
3
1
1
5 [16]). Note that a neutral hydroxo complex was
formed from six differently charged species in reac-
tion (6) with liberation of water molecules from the
hydration shells of the ions.
2
+
Cu (OH) NO + 2nNH H O = 2Cu(NH ) + 3OH
2
3
3
3
2
3 n
The potentiometric titration of the system Cu(NO ) ,
+ NO3 + 2nH O.
(10)
3
2
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 7 2002

COMPETITION OF HYDROLYSIS AND COMPLEX FORMATION
1059
To examine further changes in mCu (%), we should
note that, according to the plot of the precipitate
weight (the precipitates were taken at N 2.3, 3.1, and
4
.0) vs. N in the range of N from 1.5 to 4.0 in Fig. 3
(straight line C D ), the precipitate amount decreases,
and in poing D it dissolves almost completely (the
course of the dilatometric curve is almost repeated).
According to the X-ray phase analysis, the composi-
tion of the precipitate Cu (OH) NO remains un-
2
3
3
changed in the process. No mixed hydroxo ammine
complexes were detected. In the electronic spectra
(
Fig. 4), instead of the completely disappeaing band
at 800 nm, an absorption band appears in the range
00 625 nm (spectra of solutions 4 6), which can be
6
Fig. 5. Distribution of hydroxide and ammine complexes
+
in the heterogeneous system Cu(NO ) , (H ) NH H O
assigned, as mentioned above, to copper ammine
complexes.
3 2
3
2
2
+
H O as a function of N: (1) Cu , (2) Cu (OH) NO (s),
2
2
3
3
2
+
2+
2+
(
3) Cu(NH ) , (4) Cu(NH ) , and (5) Cu(NH ) .
3 4 3 3 3 2
Thus, the nature of the final solid product of hy-
drolytic transformations of Cu2+ ions in Cu(NO3)
Cu(NH )2 are present in the system in minor
+
2
3
solutions depends on the titrating base. In the case of
amounts. Our calculations showed that the volume
changes in the system are determined first by neutrali-
zation of the acid, then by hydrolytic reactions of
copper ions with Cu (OH) NO precipitation, and
finally by its dissolution in excess ammonia with
the formation of ammine complexes. The calculated
V values (Fig. 1, solid line) nicely agree with the
experiment.
NaOH, it is Cu(OH) , which is converted to CuO with
2
time and in excess of the base, and, in the case of
aqueous ammonia, it is Cu (OH) NO , which dis-
2
3
3
2
3
3
solves in excess ammonia to form copper ammines.
Examining Eq. (10), we can characterize the reac-
tion described by the portion CD of the dilatometric
curve as reverse of the reaction corresponding to the
portion BC, i.e., as Cu (OH) NO depolymerization
2
3
3
and dissolution. On addition of uncharged molecules
EXPERIMENTAL
of hydrated NH to one molecule of the neutral hy-
3
droxo complex, six ions are formed at once, which
causes a reduction in the volume at the expense of
their hydration.
The dilatometric titration was carried out on a pre-
cision installation; its scheme and operation principle
were described earlier [17]. The volume changes were
detected by the shift of the meniscus of a liquid in a
calibrated measuring capillary tube 0.4007 mm in di-
ameter. To ensure the stability of the volume changes,
a constant temperature of the system (25.00 0.01 C)
was maintained with two UT-2/77 ultrathermostats
and an air thermostat, connected in series.
The fact that, in the course of further titration after
passing singular point D, the molar volume does not
change noticeably (straight line DE) is due to the com-
pletion of the main chemical reactions in the system.
Dark blue Cu(NH ) (NO ) crystals (identified by
3
2
3 2
X-ray phase analysis) were obtained from the solution
For each point of the dilatometric curves, V was
at N > 4.
m
calculated from the experimental data by the follow-
The interactions revealed in the system Cu(NO ) ,
3
2
ing procedure. We determined the absolute changes
+
(
H ) NH H O H O were confirmed by CPESSP
3
3
2
2
in the volume (cm ) from the shifts s (cm) of the
model calculations. The initial model included the
meniscus of a liquid in a calibrated measuring capil-
lary tube by the formula Vabs = V1 cms (V1 cm is the
volume corresponding to 1 cm length of the capillary
tube, determined by calibration; for the capillary tube
+
2+
dissolved complexes Cu(OH) , Cu (OH) , and
2
2
Cu(NH3) 2n + (n = 1 4) with the pK values considered
above, and also Cu (OH) NO and Cu(OH) precipi-
2
3
3
2
tates. The resulting distribution of hydroxide and am-
mine complexes is given in Fig. 5. It follows from
the calculations that ammine complexes appear in
the solution at N = 1.5. Under the experimental con-
3
3
in use, V1cmM is 1.261 10 cm ). For each point,
this quantity were converted to V , equal to the ratio
m
of Vabs to the number of moles of the component
2+
+
being titrated, namely, Cu ions.
ditions, the hydroxo complex species Cu(OH) ,
3+
2+
Cu (OH) , Cu (OH) , and also the complex
The pH-metric titration in the system Cu(NO3)2
2
2
2
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 75 No. 7 2002

1060
BURKOV et al.
NH H O was carried out on an EV-74 pH meter
va, I.N., Zh. Neorg. Khim., 1982, vol. 27, no. 6,
pp. 1455 1459.
3
2
with a glass electrode. The electronic absorption spec-
tra of solutions were recorded on a Specord UV-VIS
spectrophotometer in the range 400 900 nm.
3. Burkov, K.A., Bus’ko, E.A., and Zinevich, N.I.,
Vestn. Leningr. Gos. Univ., Fiz., Khim., 1975, no. 1,
pp. 144 145.
To obtain quantitative characteristics of changes in
the volume corresponding to step complex formation,
we performed a mathematical simulation using the
CPESSP program [18, 19]. The model for processing
dilatometric data is based on an additive scheme,
which is given in [20], as applied to volume proper-
ties.
4
. Effenberger, H., Z. Kristallogr., 1983, vol. 165,
nos. 1 4, pp. 127 135.
5. Bjerrum, J., Metal Ammine Formation in Aqueous
Solution. Theory of Reversible Step Reactions, Copen-
hagen: P. Haase, 1957.
6. Gubeli, A.O., Hebert, J., Cote, P.A., and Taillon, R.,
2
+
+
Helv. Chim. Acta, 1970, vol. 53, no. 1, pp. 186 197.
The basis included the simple species Cu , H ,
+
7. Smirnova, N.I., Bus’ko, E.A., Wize, G., and Bur-
OH , NH , and NO , and the complex species NH ,
3
3
4
+
3+
2+
2+
kov, K.A., Vestn. Leningr. Gos. Univ., Fiz., Khim.,
Cu(OH) , Cu OH , Cu (OH) , Cu(NH ) (n =
2
2
2
3 n
1
987, issue 4, no. 25, pp. 83 85.
1
4), Cu (OH) NO , and Cu(OH) . The distribution
2 3 3 2
8
9
. Sidorov, Yu.V., Pykhteev, O.Yu., Burkov, K.A., et al.,
Vestn. Sankt-Peterb. Gos. Univ., Fiz., Khim., 2000,
issue 2, no. 12, pp. 81 86.
of the complexes as a function of N is given in Fig. 5,
and the comparison with the experimental data, in
Fig. 1.
. Burkov, K.A., Bus’ko, E.A., Wize, G., and Smirno-
va, N.I., Zh. Neorg. Khim, 1989, vol. 34, no. 1,
pp. 16 19.
CONCLUSION
1
1
0. Mendeleev, D.I., Rastvory (Solutions), Moscow:
By comprehensive analysis of the data obtained for
+
Akad. Nauk SSSR, 1959.
the system Cu(NO ) , (H ) NH H O H O by sev-
3
2
3
2
2
1. Millero, F.J., Water and Aqueous Solution, Structure,
Thermodynamics and Transport Processes, Horne, R.,
Ed., New York: Wiley Interscience, 1972, ch. 13,
pp. 519 565.
eral physicochemical methods, we have determined
the ranges of N corresponding to prevalence of vari-
ous chemical reactions. At N < 0, excess acid is neu-
tralized. The volume effects of the neutralization with
an alkali and with an ammonia solution differ sig-
nificantly, which is due to specific chemical features
of ammonia. At N from 0 to 1.5, the hydrolytic poly-
merization occurs, yielding the poorly soluble com-
plex Cu (OH) NO with both bases. At N > 1.5, the
1
1
2. Arat-ool, Sh.M., Chemical Interactions of Phosphonic
Acids with Various Bases in Aqueous Solutions,
Cand. Sci. (Chem.) Dissertation, St. Petersburg, 2001.
3. Stokes, R.H., Aust. J. Chem., 1975, vol. 28, no. 10,
pp. 2109 2114.
2
3
3
chemical transformations with the two bases are dif-
ferent: in titration with NaOH, solid binuclear copper
trihydroxonitrate is converted to copper hydroxide and
oxide, and in titration with NH H O, it is converted
14. Elliot, H. and Hathaway, B.J., Inorg. Chem., 1966,
vol. 5, no. 5, pp. 885 889.
15. Wendling, E., Benali-Baitich, O., and Larrat, J., Rev.
Chim. Miner., 1972, vol. 9, no. 4, pp. 607 624.
3
2
2
+
into soluble copper ammines Cu(NH ) .
3
n
16. Lo Surdo, A. and Millero, F.J., J. Phys. Chem., 1980,
vol. 84, no. 7, pp. 710 715.
ACKNOWLEDGMENTS
17. Wize, G. and Burkov, K.A., Vestn. Leningr. Gos.
Univ., Fiz., Khim., 1981, no. 10, pp. 47 52.
The authors are sincerely grateful to I.I. Kozhina
for performing the X-ray phase analyses.
1
8. Sal’nikov, Yu.I., Glebov, A.N., and Devyatov, F.V.,
Poliyadernye kompleksy v rastvorakh (Polynuclear
Complexes in Solutions), Kazan. Univ., 1989.
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