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Composition of TTA-nitro complexes of caesium
Notes
3365
another interpretation of the measured data. The relation for the surface tension represented by the line is given by Pb:
[erg/cmz] = 538-0.114-T[°K].
Direct Conversion Group Euratom Research Center Ispra ( VA ), Italy 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
J. B O H D A N S K Y H. E. J. SCHINS
G. Metzger.Z. phys. Chem. 211, I (1959). F. Sauerwald et al., Z. anorg, allg, Chem. 181,353 (1929); 223, 86 (1935), E. E. Libmann, Univ. Ill. Sta. Bull. 187 (1928). W. D. Kingery and M. Humenik,J. phys. Chem. 57,359 (1953). D. A. Timofeevicheva, V. B. Lazarev, lzvest. A kad. Nauk. 1, 147 ( 1961 ). T. R. Hogness,J. Am. chem. Soc. 43, 1621 (1921). H.T. Greeneway,J. Inst. Metall. 74, 133 (1948). L. L. Bircumshaw, Phil. Mag. 17,181 (1934);3, 1286 (1927). Y. Matuyama, Sci. Rep. Tokyo. Imp. Univ. 16,555 (1927). C. C. Addison, J. B. Raynor,J. chem. Soc. A, 965 (1966). D. A. Melford, T. P. Hoar,J. Inst. Metall. 85, 197 (1956/57). E. Flechsig, VDI Zs 107, 1227 (1965). K. Monma, H. Suto, Trans. Jap. Inst. Metall. 1, 69 (1960). F. Sauerwatd et al., Z. anorg. A llg. Chem. 162, 301 (1927); 154, 79 (1926).
J. inorg,nucl.Chem.,1968,Vol.30. pp. 3365to 3368. PergamonPress. Printedin GreatBritain
Composition of TTA-nitro complexes of caesium (First received 13 February 1968; in revised form 22 April 1968) IN AN earlier publication[l] it was shown that Cs could be extracted into organic solvents from aqueous media by means of "l~A (thenoyl trifluoro-acetone) on the addition of organo-nitro compounds. The purpose of the present study was to investigate the nature of the extracting species. The extraction times and procedures using lsTCs as tracer have already been described[l]. The exact experimental conditions are given in the legends of Figs. 1 and 2. Maximum extraction was attained within l rain, so extraction times were always confined to less than 3 min in order to avoid any possible complications due to the hydrolysis of the TTA. The anomalous hydrolysis behaviour of TTA in alkali media has been fully discussed in previous publications [ 1-4]. TTA reacts with most metal ions to form unionised chelate compounds soluble in organic solvents and immiscible with water. Because of their large size and small charge, the alkali metals form saltlike derivatives of fl-diketones which are insoluble in hydrocarbon solvents. However, the addition of sufficient neutral molecules to satisfy apparent coordination numbers for the alkali metal ion of 4 o r 6, imparts some complex character. Thus, sodium benzoyt acetonate is insoluble in toluene but the 2-hydrate is soluble [5]. Many of these alkali metal derivatives which are insoluble in organic solvents readily dissolve in the presence of excess of the mother substance by forming 4 or 6 coordinated complexes. I. 2. 3. 4. 5.
P. Crowther and F. L. Moore,Ann. Chem. 35, 2081 (1963). E. Zebrowski, U S A E C Rep. No. BC-63 (1947). E. H. Cook. W. Taft, Jr.,J.Am. chem. Soc. 74, 6103 (1952). E. L. King and W. H. Reas, J. Am. chem. Soc. 73, 1806 ( 1951 ). T. Moeller, Inorganic Chemistry. Wiley, New York (1959).
3366
Notes
1.0
A
SIo
0,1
0.01
0"I
1.0
I~TA 3 ,~ M Fig. 1. Cs distribution as a function of T T A concentration. A = 3.9 M nitrobenzene; B = 5-6 M nitromethane. Organic - volume = I. Aqueous Organic diluent xylene. Aqueous phase: 0.5 M NaOH.
The above facts suggest the possible role of the nitro group in the extraction of Cs by TTA; namely by raising the effective coordination number of the metal ion. The formation of the extracing complex may be considered as follows: CS+q + TTA~q + n($NO2)o~ m Cs(TTA)(~NO2).o,~ where ~ represents a methyl or phenyl group.
( 1)
Notes
3367
1.0
I'0
Slope
=
4
0"1
O'O I
io
EC6H 5N02 "-] ~M Fig. 2. Cs distribution as a function o f nitrobenzene concentration.
Organic - volume = 1. Aqueous Organic phase: 0.25 M TTA-xylene. Aquoues phase: 0.5 M NaOH.
The distribution coefficient is given by C s org. D = - CSaq.
(2)
From Equation (1) it follows [Cs(TTA) (~bN0 2),,]o~. kl = [Cs+laq.iTTA_la,.[ckNO2]g,g ..
~3)
3368
Notes
Thus D may be rewritten
(4)
log D = log kl + log [TTA -]aq + n log (~bNO~).
In the above relation (4) kl is a constant. The first power dependence of D on [TTA] at constant nitro concentration is shown in Fig. I. The value of n = 4 was obtained from the slope in Fig. 2, where log D is plotted against log [~bNO2] at a constant q T A concentration. From the above facts a possible structure for C s(TI'A) (qbNO2)4 in the form of a 6 co-ordinated alkali metal chelate is proposed. However, it must be remembered that the above conclusions refer to data derived from concentrated solutions which cannot be assumed to be ideal.
National Nuclear Research Centre Pelindaba Pretoria
P. C R O W T H E R A. J U R R I A A N S E
J. inorg,nucl.Chem., 1968,Vol.30. pp. 3368to 3373. PergamonPress. Printedin Great Britain
Electrometric studies on the composition and stability constants of zinc-/3-Mercapto-propionic acid complexes (First received 1April 1968; in revised form 8 May 1968) THE ZINC complexes of fl-Mercapto-propionic acid have been investigated by potentiometric and conductometric titration techniques in aqueous 0" l M KNO3. it was found that Zn ~+ forms two colourless complexes; 1 : 1 predominating at pH 6.5-7.0 and 1:2 at pH 8.0-9.5. The log K values for these complexes have been computed by alternative methods at 20, 30 and 40°C. The overall changes in AG, AH and AS accompanying the reaction have also been reported. There is no reference available in the literature on the study of zinc complexes of/3-Mercapto propionic acid (referred to herein as MPA), their stability constants and other thermodynamic functions. Hence the present investigation has been undertaken. fl-Mercapto propionic acid (99-1% Evan's Chemetics Inc., New York) and Anal-R (BDH) reagents ZnSO4, KNO3, NaOH etc., were used and their solutions prepared in doubly distilled air-free conductivity water. An approximately2 x 10-2 M solution of MPA was prepared and standardised by potentiometric titration with standard NaOH. The zinc content in zinc sulphate solution was checked by estimating it as zinc pyrophospbate [ 1]. A Cambridge bench pattern (null deflection type) pH-meter with universal glass and dip type calomel electrodes was used for pH-measurements and calibrated by using several solutions 10-2 and 10-a M HCIO4 with ionic strength 0-1 M (obtained by the addition of NaC104). Thus the reading gave immediately concentrations and not the activities of H ÷. Before and after each series of measurements, a calibration was made. Though the meter can measure 0.01 unit of pH, it is supposed that with the error inherent in calibration, the ultimate, error is _+0.02 pH unit. A CO2-free nitrogen atmosphere (Pre-saturated with 0-1 M KNOa) was maintained above the solution throughout the titrations. All the pH titrations were performed in aqueous 0. l M KNO3. The experimental procedure, as described earlier [2-5], involved a series of pH and conductometric I. A. |l Vogel, A Text book of Quantitative Inorganic Analysis, pp. 532-33. Longmans Green, London (1961 ). 2. R. S. Saxena, K. C. Gupta and M. L. Mittal, J. inorg, nucl. Chem. 30, 189 (1968). 3. R.S. Saxena, K. C. Gupta and M. L. Mittal, Can. J. Chem. 46, 311 (1968). 4. R.S. Saxena, K. C. Gupta and M. L. MittaI,Aust.J. Chem. 21 (3), 641 (1968). 5. R, S. Saxena and K. C. Gupta, J. Indian chem. Soc. In press.
3365
another interpretation of the measured data. The relation for the surface tension represented by the line is given by Pb:
[erg/cmz] = 538-0.114-T[°K].
Direct Conversion Group Euratom Research Center Ispra ( VA ), Italy 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.
J. B O H D A N S K Y H. E. J. SCHINS
G. Metzger.Z. phys. Chem. 211, I (1959). F. Sauerwald et al., Z. anorg, allg, Chem. 181,353 (1929); 223, 86 (1935), E. E. Libmann, Univ. Ill. Sta. Bull. 187 (1928). W. D. Kingery and M. Humenik,J. phys. Chem. 57,359 (1953). D. A. Timofeevicheva, V. B. Lazarev, lzvest. A kad. Nauk. 1, 147 ( 1961 ). T. R. Hogness,J. Am. chem. Soc. 43, 1621 (1921). H.T. Greeneway,J. Inst. Metall. 74, 133 (1948). L. L. Bircumshaw, Phil. Mag. 17,181 (1934);3, 1286 (1927). Y. Matuyama, Sci. Rep. Tokyo. Imp. Univ. 16,555 (1927). C. C. Addison, J. B. Raynor,J. chem. Soc. A, 965 (1966). D. A. Melford, T. P. Hoar,J. Inst. Metall. 85, 197 (1956/57). E. Flechsig, VDI Zs 107, 1227 (1965). K. Monma, H. Suto, Trans. Jap. Inst. Metall. 1, 69 (1960). F. Sauerwatd et al., Z. anorg. A llg. Chem. 162, 301 (1927); 154, 79 (1926).
J. inorg,nucl.Chem.,1968,Vol.30. pp. 3365to 3368. PergamonPress. Printedin GreatBritain
Composition of TTA-nitro complexes of caesium (First received 13 February 1968; in revised form 22 April 1968) IN AN earlier publication[l] it was shown that Cs could be extracted into organic solvents from aqueous media by means of "l~A (thenoyl trifluoro-acetone) on the addition of organo-nitro compounds. The purpose of the present study was to investigate the nature of the extracting species. The extraction times and procedures using lsTCs as tracer have already been described[l]. The exact experimental conditions are given in the legends of Figs. 1 and 2. Maximum extraction was attained within l rain, so extraction times were always confined to less than 3 min in order to avoid any possible complications due to the hydrolysis of the TTA. The anomalous hydrolysis behaviour of TTA in alkali media has been fully discussed in previous publications [ 1-4]. TTA reacts with most metal ions to form unionised chelate compounds soluble in organic solvents and immiscible with water. Because of their large size and small charge, the alkali metals form saltlike derivatives of fl-diketones which are insoluble in hydrocarbon solvents. However, the addition of sufficient neutral molecules to satisfy apparent coordination numbers for the alkali metal ion of 4 o r 6, imparts some complex character. Thus, sodium benzoyt acetonate is insoluble in toluene but the 2-hydrate is soluble [5]. Many of these alkali metal derivatives which are insoluble in organic solvents readily dissolve in the presence of excess of the mother substance by forming 4 or 6 coordinated complexes. I. 2. 3. 4. 5.
P. Crowther and F. L. Moore,Ann. Chem. 35, 2081 (1963). E. Zebrowski, U S A E C Rep. No. BC-63 (1947). E. H. Cook. W. Taft, Jr.,J.Am. chem. Soc. 74, 6103 (1952). E. L. King and W. H. Reas, J. Am. chem. Soc. 73, 1806 ( 1951 ). T. Moeller, Inorganic Chemistry. Wiley, New York (1959).
3366
Notes
1.0
A
SIo
0,1
0.01
0"I
1.0
I~TA 3 ,~ M Fig. 1. Cs distribution as a function of T T A concentration. A = 3.9 M nitrobenzene; B = 5-6 M nitromethane. Organic - volume = I. Aqueous Organic diluent xylene. Aqueous phase: 0.5 M NaOH.
The above facts suggest the possible role of the nitro group in the extraction of Cs by TTA; namely by raising the effective coordination number of the metal ion. The formation of the extracing complex may be considered as follows: CS+q + TTA~q + n($NO2)o~ m Cs(TTA)(~NO2).o,~ where ~ represents a methyl or phenyl group.
( 1)
Notes
3367
1.0
I'0
Slope
=
4
0"1
O'O I
io
EC6H 5N02 "-] ~M Fig. 2. Cs distribution as a function o f nitrobenzene concentration.
Organic - volume = 1. Aqueous Organic phase: 0.25 M TTA-xylene. Aquoues phase: 0.5 M NaOH.
The distribution coefficient is given by C s org. D = - CSaq.
(2)
From Equation (1) it follows [Cs(TTA) (~bN0 2),,]o~. kl = [Cs+laq.iTTA_la,.[ckNO2]g,g ..
~3)
3368
Notes
Thus D may be rewritten
(4)
log D = log kl + log [TTA -]aq + n log (~bNO~).
In the above relation (4) kl is a constant. The first power dependence of D on [TTA] at constant nitro concentration is shown in Fig. I. The value of n = 4 was obtained from the slope in Fig. 2, where log D is plotted against log [~bNO2] at a constant q T A concentration. From the above facts a possible structure for C s(TI'A) (qbNO2)4 in the form of a 6 co-ordinated alkali metal chelate is proposed. However, it must be remembered that the above conclusions refer to data derived from concentrated solutions which cannot be assumed to be ideal.
National Nuclear Research Centre Pelindaba Pretoria
P. C R O W T H E R A. J U R R I A A N S E
J. inorg,nucl.Chem., 1968,Vol.30. pp. 3368to 3373. PergamonPress. Printedin Great Britain
Electrometric studies on the composition and stability constants of zinc-/3-Mercapto-propionic acid complexes (First received 1April 1968; in revised form 8 May 1968) THE ZINC complexes of fl-Mercapto-propionic acid have been investigated by potentiometric and conductometric titration techniques in aqueous 0" l M KNO3. it was found that Zn ~+ forms two colourless complexes; 1 : 1 predominating at pH 6.5-7.0 and 1:2 at pH 8.0-9.5. The log K values for these complexes have been computed by alternative methods at 20, 30 and 40°C. The overall changes in AG, AH and AS accompanying the reaction have also been reported. There is no reference available in the literature on the study of zinc complexes of/3-Mercapto propionic acid (referred to herein as MPA), their stability constants and other thermodynamic functions. Hence the present investigation has been undertaken. fl-Mercapto propionic acid (99-1% Evan's Chemetics Inc., New York) and Anal-R (BDH) reagents ZnSO4, KNO3, NaOH etc., were used and their solutions prepared in doubly distilled air-free conductivity water. An approximately2 x 10-2 M solution of MPA was prepared and standardised by potentiometric titration with standard NaOH. The zinc content in zinc sulphate solution was checked by estimating it as zinc pyrophospbate [ 1]. A Cambridge bench pattern (null deflection type) pH-meter with universal glass and dip type calomel electrodes was used for pH-measurements and calibrated by using several solutions 10-2 and 10-a M HCIO4 with ionic strength 0-1 M (obtained by the addition of NaC104). Thus the reading gave immediately concentrations and not the activities of H ÷. Before and after each series of measurements, a calibration was made. Though the meter can measure 0.01 unit of pH, it is supposed that with the error inherent in calibration, the ultimate, error is _+0.02 pH unit. A CO2-free nitrogen atmosphere (Pre-saturated with 0-1 M KNOa) was maintained above the solution throughout the titrations. All the pH titrations were performed in aqueous 0. l M KNO3. The experimental procedure, as described earlier [2-5], involved a series of pH and conductometric I. A. |l Vogel, A Text book of Quantitative Inorganic Analysis, pp. 532-33. Longmans Green, London (1961 ). 2. R. S. Saxena, K. C. Gupta and M. L. Mittal, J. inorg, nucl. Chem. 30, 189 (1968). 3. R.S. Saxena, K. C. Gupta and M. L. Mittal, Can. J. Chem. 46, 311 (1968). 4. R.S. Saxena, K. C. Gupta and M. L. MittaI,Aust.J. Chem. 21 (3), 641 (1968). 5. R, S. Saxena and K. C. Gupta, J. Indian chem. Soc. In press.