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Equilibria of ZnCl2 in molten KCl(sat.)-acetamide
Notes
3641
rise to only one i.r. active band in the above said region, these may be regarded to have trans structure of coordination number six. The fifth complex shows an additional band at 425 cm-. 1 which is attributed to P b - O stretch in view of the previous assignments[7] showing that it has trans structure of coordination number six. Acknowledgement--One of the authors (NNS) is grateful to the Karnatak University for the award of University Studentship. Department of Chemistry Karnatak University Dharwar- 3 India
N . S . BIRADAR* N . N . SIRMOKADAM
* To whom all the correspondence should be addressed. 7. (a) N. S. Biradar and V. H. Kulkarni, Z. anorg, allg. Chem. 387, 275 (1972); Proc. D.A.E. Chem., Symp., Vol. 1. p. 270 (1969). (b) N. S. Biradar, V. H. Kulkarni and N. N. Sirmokadam, J. inorg, nucl. Chem. 34, 3651 (1972).
J. inorg,nucL Chem., 1973,VoL 35, pp. 3641-3644."PergamonPress. Printed in Great Britain.
Equilibria of ZnCI z in molten KCl(sat.)-acetamide (Received 8 January 1973) SATURATI:D KCl-acetamide solution is very important as the fused electrolyte in high-temperature silver chloride-zinc thermal batteries [1, 2]. Conductometric analysis has been employed to examine the zinc chloride equilibria in fused KCl(sat.)-acetamide solutions. Jander and Winider [3] have reviewed the general physical and chemical properties of acetamide in its molten state. In this note, the extent of specific conductance variations of zinc chloride in saturated KCl-acetamide molten solutions are presented over the temperature range from 85 to 135°C. For comparison, the specific conductances of the simple ZnClzacetamide solutions have also been measured. Conductance deviations in the mixed ZnCIz-KCl(sat.)acetamide are discussed in terms of chlorozinc complex ion formations and increased viscosity of the acetamide electrolyte. EXPERIMENTAL Conductances were measured at 1000 cycles with a shielded Jones bridge. A standard dipping ceil, which had a cell constant of 0-1055 cm- t as determined by the method of Jones and Bradshaw [4] was used. Allresistance measurements were made with the cell held in a silicone oil bath which was maintained at a constant temperature within +0.1°C. The conductance cell was sealed on the side of a 500 ml conical flask closed by a ground-glass stopper fitted with a side arm through which prepurified dry nitrogen was passed to prevent the admission of air into the cell when the molten acetamide salt solutions were added to the cell.
1. 2. 3. 4.
R. R. G. G.
A. Wallace and P. F. Bruins, J. electrochem. Soc. 114, 209 (1967). A. Wallace and P. F. Bruins, J. electrochem. Soc. 114,212 (1967). Jander and G. Winkler, J. inorg, nucl. Chem. 9, 24 (1959), Jones and B. G. Bradshaw, d. Am. chem. Soc. 55, 1780 (1933).
3642
Notes
Acetamide solutions Analytical grade acetamide crystals (Mallinckrodt Chemical) were further purified by recrystallization in pure benzene. The resulting solvent (m.p. 80.0°C) had a mean specific conductance of 8.3 x 10 -6 f l - 1 croat 94°C. Analytical grade KCI and ZnCI2 (Baker and Adamson) were used without further purification; the salts were dried at about 150°C and the dried salts kept in a desiccator. RESULTS AND DISCUSSION In Fig. 1 are presented the specific conductance results for the molten ZnCi2-KCl(+at.)-acetamide solutions, as a function of zinc salt content and temperature. The electrical conductivity is markedly diminished when zinc chloride is added in small amounts. On further additions, the conductivity underwent a minimum and then increased fairly rapidly thereafter until it reached a maximum value occurring in the 1-3 M zinc chloride region. These conductance variations resulted in minimum-maximum conductance curves, and were attributed to the formation of chlorozine complex ions of lower ionic mobility than the more mobile chloride anion in the saturated KCl-acetamide electrolyte. As is shown in Fig. 1, the precise location of the minima and maxima points depend on the temperature and the amount of KCI in acetamide. For comparison, the specific conductance data are presented in Fig. 2 for the simpler ZaCl2-acetamide electrolyte. Figure 2 shows the results of the specific conductance of the ZnClz-acetamide system as a function of zinc salt concentration with temperature as a parameter. Our conductance data indicates that zinc chloride behaves as an intermediate electrolyte in molten acetamide solutions. The conductance maxima, as are shown in the concentrated zinc chloride region in Fig. 2, were attributed to increasing melt viscosity and chlorozine complex formation effects, and were in direct proportion to the temperature of the fused aeetamide solutions. At these high 1-3 M zinc salt concentrations, there is not enough solvent acetamide molecules to go around; that is, to both solvate the ions and to provide the medium through which the ions move. "The result seems to be that the acetamide solution becomes a continuum of solvated ions with little or no free solvent. Thereupon, the mobility of the solvated ions is retarded because of increased resistance offered by the acetamide solution medium. In addition, as zinc chloride is added to the concentrated ZnClzacetamide solution, the mobility of the remaining ions is reduced owing to chlorozine complex formation. These two effects lowered the conductivity and hence contributed to the observed maxima as is shown in Fig. 2.
Solutions •-e
n
n
% K ° u c
135oC
125"C
14 115"C
~'
,
_u
I0
g ~" Q. U)
8
105"C
95°C "~
'
~
85"C
I
I
I
t
I
0.5
1.0
1.5
2-0
2.5
Zinc
chloride
mololity
Fig. 1. Specific conductance of molten ZnClz-KCl(sat.)-acetamide solutions.
Notes
3643
ZnCIz-Acetomide
solutions
8--
mO
x 7_o~ 6 - - e 120 C 'u
I
2 ul
I 0
I
[
,
I Zinc
chloride
I
L
2
I
3
mololity
Fig. 2. Specific conductance of molten ZnCl2-acetamide solutions. The conductance minima, observed upon the additions of small amounts of zinc chloride to the saturated KCl-acetamide solution, could either be caused by a reduction of the number of ions, or by the formation of complex ions of lower ionic mobility than the chloride ions. It is likely that the chlorozinc complexes dissociate with increasing temperature and thereby put more ions into solution. It is also more probable that zinc chloride forms complex ions of lower ionic mobility thai1 the chloride ions. The reaction of such chloro-zinc complex formation in fused KCl-acetamide solution likely involves the transfer of chloride ions according to ZnCI2 + xCl- ~ ZnCI~.2), where x is a function of KCI concentration. Moreover, in view of the fact that lower conductances for the mixed ZnC12-KCl(sat. )acetamide system occurred at zinc salt concentration under about 0"2 molality; it is evident that the zinc salt removes the more mobile chloride ions from solution by means of complex formation, replacing them with less mobile chlorozinc complexes. The conductance maxima observed in the mixed molten acetamide system can be attributed to increased viscosity and complex formation effects, that were discussed previously for the simpler ZnCl2-acetamide system. The main difference between the~e two systems is the presence of potassium chloride which, at high zinc chloride concentrations, is essentially cancelled out as a separate conducting species through complexation with zinc chloride. Additional information on the nature of the predominant chloro-zinc complexes existing in the mixed ZnCi2-KCl(sat.)-acetamide was obtained by a conductometric titration determination. In this titration the resistance of a dilute 0.050 M ZnCI2 fused acetamide solution at 100°C was measured after each addition of solid potassium chloride. Figure 2 presents these titration data and gives the corresponding .. F molality KCI added -] . . molality . . ZnCI211 conductances as a function of molality rauo L 10.050
g
¢1 u)
I
I
I
2
I
3
L
MoIollty ratio Mololit~t of potassium chloride added 0 . 0 5 0 Molol zinc chloride
Fig. 3. Conductometric titration of 0-050 M zinc chloride in molten acetamide with potassium chloride at 100°C.
3644
Notes
In Fig. 3, two straight lines intersected at a 2.0 M ratio end point. This indicates that two moles of KCI was required to combine with one mole of ZnC12 for the probable formation of the chloro-zincate complex, ZnCI~ in fused acetamide. As the KC1 reacted with the weak ZnCI 2 electrolyte, the more mobile reaction product, ZnCI~ formed. As the molten mixed acetamide electrolyte becomes progressively more concentrated in zinc chloride, a combination of chlorozinc complex ions as well as zinc chloride molecules likely prevails. Acknowledgement--This work was supported in part by the Stanford University Center for Materials Research, and by the Office of Naval Research. Department of Materials Science and Engineering Stanford University Stanford, California 94305
RICHARD A. WALLACE
j. inorg,nucl. Chem., 1973,Vol. 35, pp. 3644-3648. PergamonPress. Printedin Great Britain.
Studies on oxofluoromolybdates(VI) with organic basic cations (First received 18 September 1972; in revised form 8 January 1973) ALTHOUGH various types of oxofluoromolybdates(VI), viz. [MoO3F]-, [MoO3F2] 2-, [MoO2F3] -, [MoO3F3] 3-, [MoO2F4] 2-, [MoOFs]- and [MoO2Fs] 3- have been reported[l, 2], only a few chemical and physical data of these compounds are available and it is difficult to judge the credibility of some of the claims[3]. In recent years the existence of salts of the types [M602F4] 2- and [MoOFs]- has been confirmed and the crystal structure of a few salts studied[4-8]. Very few salts mostly with inorganic simple cations have been reported for each series. The low solubility of many fluorides and molybdates of inorganic ions often makes the crystallization of fluoromolybdates difficult from aqueous solution. The availability of a large number of organic base fluorides soluble in water-or in aqueous hydrofluoric acid leads to the possibility of preparing a wide number of oxofluoromolybdates from aqueous medium. Since the size and the charge of the organic basic cations can be varied to a great extent by suitable choice of the base, it can also be examined whether these factors have any influence on the formation of the different types of the oxofluoromolybdates(VI). In this communication we are presenting the results of our studies on the isolation and the properties of a number of oxofluoromolybdates(VI) with organic nitrogeneous basic cations, most of the salts belonging to the type [MoO2F4] 2-. EXPERIMENTAL Molybdenum trioxide was prepared by heating ammonium molybdate (analytical reagent grade of J. T. Baker Chemical Co. Phillipsburg) at 500°. Phenyl biguanide hydrochloride was prepared by standard 1. N.V. Sidgwick, The Chemical Elements and Their Compounds, Vol. 2, p. 1044. Oxford University Press, Oxford (1962). 2. J. W. Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry, Vol. II, p. 612. Longroans, Green, London (1948). 3. J. H. Canterford and R. Colton, Halides o f the Secondand Third Row Transition Metals, p. 242. John Wiley, New York (1968). 4. G. B. Hargreaves and R. D. Peacock, J. chem. Soc. 2170 (1958). 5. G. B. Hargreaves and R. D. Peacock, J. chem. Soc. 4390 (1958). 6. D. Grandjean and R. Weiss, C.r.hebd. Sdanc..4cad. Sci. Paris 262C, 1964 (1966). 7. D. Grandjean and R. Weiss, Bull. Soc. chim. Fr. 3049 (1967). 8. J. Fischer, A. DeCian and R. Weiss, Bull. Soc. chim. Fr. 2646 (1966).
3641
rise to only one i.r. active band in the above said region, these may be regarded to have trans structure of coordination number six. The fifth complex shows an additional band at 425 cm-. 1 which is attributed to P b - O stretch in view of the previous assignments[7] showing that it has trans structure of coordination number six. Acknowledgement--One of the authors (NNS) is grateful to the Karnatak University for the award of University Studentship. Department of Chemistry Karnatak University Dharwar- 3 India
N . S . BIRADAR* N . N . SIRMOKADAM
* To whom all the correspondence should be addressed. 7. (a) N. S. Biradar and V. H. Kulkarni, Z. anorg, allg. Chem. 387, 275 (1972); Proc. D.A.E. Chem., Symp., Vol. 1. p. 270 (1969). (b) N. S. Biradar, V. H. Kulkarni and N. N. Sirmokadam, J. inorg, nucl. Chem. 34, 3651 (1972).
J. inorg,nucL Chem., 1973,VoL 35, pp. 3641-3644."PergamonPress. Printed in Great Britain.
Equilibria of ZnCI z in molten KCl(sat.)-acetamide (Received 8 January 1973) SATURATI:D KCl-acetamide solution is very important as the fused electrolyte in high-temperature silver chloride-zinc thermal batteries [1, 2]. Conductometric analysis has been employed to examine the zinc chloride equilibria in fused KCl(sat.)-acetamide solutions. Jander and Winider [3] have reviewed the general physical and chemical properties of acetamide in its molten state. In this note, the extent of specific conductance variations of zinc chloride in saturated KCl-acetamide molten solutions are presented over the temperature range from 85 to 135°C. For comparison, the specific conductances of the simple ZnClzacetamide solutions have also been measured. Conductance deviations in the mixed ZnCIz-KCl(sat.)acetamide are discussed in terms of chlorozinc complex ion formations and increased viscosity of the acetamide electrolyte. EXPERIMENTAL Conductances were measured at 1000 cycles with a shielded Jones bridge. A standard dipping ceil, which had a cell constant of 0-1055 cm- t as determined by the method of Jones and Bradshaw [4] was used. Allresistance measurements were made with the cell held in a silicone oil bath which was maintained at a constant temperature within +0.1°C. The conductance cell was sealed on the side of a 500 ml conical flask closed by a ground-glass stopper fitted with a side arm through which prepurified dry nitrogen was passed to prevent the admission of air into the cell when the molten acetamide salt solutions were added to the cell.
1. 2. 3. 4.
R. R. G. G.
A. Wallace and P. F. Bruins, J. electrochem. Soc. 114, 209 (1967). A. Wallace and P. F. Bruins, J. electrochem. Soc. 114,212 (1967). Jander and G. Winkler, J. inorg, nucl. Chem. 9, 24 (1959), Jones and B. G. Bradshaw, d. Am. chem. Soc. 55, 1780 (1933).
3642
Notes
Acetamide solutions Analytical grade acetamide crystals (Mallinckrodt Chemical) were further purified by recrystallization in pure benzene. The resulting solvent (m.p. 80.0°C) had a mean specific conductance of 8.3 x 10 -6 f l - 1 croat 94°C. Analytical grade KCI and ZnCI2 (Baker and Adamson) were used without further purification; the salts were dried at about 150°C and the dried salts kept in a desiccator. RESULTS AND DISCUSSION In Fig. 1 are presented the specific conductance results for the molten ZnCi2-KCl(+at.)-acetamide solutions, as a function of zinc salt content and temperature. The electrical conductivity is markedly diminished when zinc chloride is added in small amounts. On further additions, the conductivity underwent a minimum and then increased fairly rapidly thereafter until it reached a maximum value occurring in the 1-3 M zinc chloride region. These conductance variations resulted in minimum-maximum conductance curves, and were attributed to the formation of chlorozine complex ions of lower ionic mobility than the more mobile chloride anion in the saturated KCl-acetamide electrolyte. As is shown in Fig. 1, the precise location of the minima and maxima points depend on the temperature and the amount of KCI in acetamide. For comparison, the specific conductance data are presented in Fig. 2 for the simpler ZaCl2-acetamide electrolyte. Figure 2 shows the results of the specific conductance of the ZnClz-acetamide system as a function of zinc salt concentration with temperature as a parameter. Our conductance data indicates that zinc chloride behaves as an intermediate electrolyte in molten acetamide solutions. The conductance maxima, as are shown in the concentrated zinc chloride region in Fig. 2, were attributed to increasing melt viscosity and chlorozine complex formation effects, and were in direct proportion to the temperature of the fused aeetamide solutions. At these high 1-3 M zinc salt concentrations, there is not enough solvent acetamide molecules to go around; that is, to both solvate the ions and to provide the medium through which the ions move. "The result seems to be that the acetamide solution becomes a continuum of solvated ions with little or no free solvent. Thereupon, the mobility of the solvated ions is retarded because of increased resistance offered by the acetamide solution medium. In addition, as zinc chloride is added to the concentrated ZnClzacetamide solution, the mobility of the remaining ions is reduced owing to chlorozine complex formation. These two effects lowered the conductivity and hence contributed to the observed maxima as is shown in Fig. 2.
Solutions •-e
n
n
% K ° u c
135oC
125"C
14 115"C
~'
,
_u
I0
g ~" Q. U)
8
105"C
95°C "~
'
~
85"C
I
I
I
t
I
0.5
1.0
1.5
2-0
2.5
Zinc
chloride
mololity
Fig. 1. Specific conductance of molten ZnClz-KCl(sat.)-acetamide solutions.
Notes
3643
ZnCIz-Acetomide
solutions
8--
mO
x 7_o~ 6 - - e 120 C 'u
I
2 ul
I 0
I
[
,
I Zinc
chloride
I
L
2
I
3
mololity
Fig. 2. Specific conductance of molten ZnCl2-acetamide solutions. The conductance minima, observed upon the additions of small amounts of zinc chloride to the saturated KCl-acetamide solution, could either be caused by a reduction of the number of ions, or by the formation of complex ions of lower ionic mobility than the chloride ions. It is likely that the chlorozinc complexes dissociate with increasing temperature and thereby put more ions into solution. It is also more probable that zinc chloride forms complex ions of lower ionic mobility thai1 the chloride ions. The reaction of such chloro-zinc complex formation in fused KCl-acetamide solution likely involves the transfer of chloride ions according to ZnCI2 + xCl- ~ ZnCI~.2), where x is a function of KCI concentration. Moreover, in view of the fact that lower conductances for the mixed ZnC12-KCl(sat. )acetamide system occurred at zinc salt concentration under about 0"2 molality; it is evident that the zinc salt removes the more mobile chloride ions from solution by means of complex formation, replacing them with less mobile chlorozinc complexes. The conductance maxima observed in the mixed molten acetamide system can be attributed to increased viscosity and complex formation effects, that were discussed previously for the simpler ZnCl2-acetamide system. The main difference between the~e two systems is the presence of potassium chloride which, at high zinc chloride concentrations, is essentially cancelled out as a separate conducting species through complexation with zinc chloride. Additional information on the nature of the predominant chloro-zinc complexes existing in the mixed ZnCi2-KCl(sat.)-acetamide was obtained by a conductometric titration determination. In this titration the resistance of a dilute 0.050 M ZnCI2 fused acetamide solution at 100°C was measured after each addition of solid potassium chloride. Figure 2 presents these titration data and gives the corresponding .. F molality KCI added -] . . molality . . ZnCI211 conductances as a function of molality rauo L 10.050
g
¢1 u)
I
I
I
2
I
3
L
MoIollty ratio Mololit~t of potassium chloride added 0 . 0 5 0 Molol zinc chloride
Fig. 3. Conductometric titration of 0-050 M zinc chloride in molten acetamide with potassium chloride at 100°C.
3644
Notes
In Fig. 3, two straight lines intersected at a 2.0 M ratio end point. This indicates that two moles of KCI was required to combine with one mole of ZnC12 for the probable formation of the chloro-zincate complex, ZnCI~ in fused acetamide. As the KC1 reacted with the weak ZnCI 2 electrolyte, the more mobile reaction product, ZnCI~ formed. As the molten mixed acetamide electrolyte becomes progressively more concentrated in zinc chloride, a combination of chlorozinc complex ions as well as zinc chloride molecules likely prevails. Acknowledgement--This work was supported in part by the Stanford University Center for Materials Research, and by the Office of Naval Research. Department of Materials Science and Engineering Stanford University Stanford, California 94305
RICHARD A. WALLACE
j. inorg,nucl. Chem., 1973,Vol. 35, pp. 3644-3648. PergamonPress. Printedin Great Britain.
Studies on oxofluoromolybdates(VI) with organic basic cations (First received 18 September 1972; in revised form 8 January 1973) ALTHOUGH various types of oxofluoromolybdates(VI), viz. [MoO3F]-, [MoO3F2] 2-, [MoO2F3] -, [MoO3F3] 3-, [MoO2F4] 2-, [MoOFs]- and [MoO2Fs] 3- have been reported[l, 2], only a few chemical and physical data of these compounds are available and it is difficult to judge the credibility of some of the claims[3]. In recent years the existence of salts of the types [M602F4] 2- and [MoOFs]- has been confirmed and the crystal structure of a few salts studied[4-8]. Very few salts mostly with inorganic simple cations have been reported for each series. The low solubility of many fluorides and molybdates of inorganic ions often makes the crystallization of fluoromolybdates difficult from aqueous solution. The availability of a large number of organic base fluorides soluble in water-or in aqueous hydrofluoric acid leads to the possibility of preparing a wide number of oxofluoromolybdates from aqueous medium. Since the size and the charge of the organic basic cations can be varied to a great extent by suitable choice of the base, it can also be examined whether these factors have any influence on the formation of the different types of the oxofluoromolybdates(VI). In this communication we are presenting the results of our studies on the isolation and the properties of a number of oxofluoromolybdates(VI) with organic nitrogeneous basic cations, most of the salts belonging to the type [MoO2F4] 2-. EXPERIMENTAL Molybdenum trioxide was prepared by heating ammonium molybdate (analytical reagent grade of J. T. Baker Chemical Co. Phillipsburg) at 500°. Phenyl biguanide hydrochloride was prepared by standard 1. N.V. Sidgwick, The Chemical Elements and Their Compounds, Vol. 2, p. 1044. Oxford University Press, Oxford (1962). 2. J. W. Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry, Vol. II, p. 612. Longroans, Green, London (1948). 3. J. H. Canterford and R. Colton, Halides o f the Secondand Third Row Transition Metals, p. 242. John Wiley, New York (1968). 4. G. B. Hargreaves and R. D. Peacock, J. chem. Soc. 2170 (1958). 5. G. B. Hargreaves and R. D. Peacock, J. chem. Soc. 4390 (1958). 6. D. Grandjean and R. Weiss, C.r.hebd. Sdanc..4cad. Sci. Paris 262C, 1964 (1966). 7. D. Grandjean and R. Weiss, Bull. Soc. chim. Fr. 3049 (1967). 8. J. Fischer, A. DeCian and R. Weiss, Bull. Soc. chim. Fr. 2646 (1966).