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The direct determination of the normal boiling point of tin
232
Letters to the editors
Preparation of
cis-dinitrobis(ethylenediamine)eobalt(III)
nitrite
(Received 13 August 1962) S~VERAL preparations of salts of the [Co(en),(NO2)2] + ion have been reported in the literature. The most usual is that of WERNER~1> as modified by HOLTZCLAW et al., c~ beginning with potassium hexanitroeobaltate. However, this method has several disadvantages including a starting material which is difficult to prepare in high purity and to dry thoroughly; critical temperature control; and low yield (12-15 per cent). Since the compound is not only interesting in its own right, being stable and resolvable, but is also the resolving agent recently applied most successfully to the resolution of the ethylene-dinitrilotetraacetatocobaltate ion, TM a simpler synthesis is desirable. A method using trans-dichlorobis(ethylenediamine)cobalt(III) chloride requires a much shorter time and is at least twice as efficient. EXPERIMENTAL Thirty grams of trans-dichlorobis(ethylenediamine)cobalt(III) chloride 14~ are dissolved with magnetic stirring in 150 ml cold H20. When the salt is dissolved, the solution is cooled to about --12 ° in an ice-salt bath and 114 g of powdered NaNO, added over 1 or 2 min while stirring fairly rapidly. The solution changes from green to red and before all the salt has been added is bright orange-brown with the suspension of the desired cis-salt. The mixture is cooled and stirred 30 min longer, filtered quickly, the precipitate washed once with 20-30 ml of cold water, twice with 20-30 ml portions of absolute ethanol, and twice with similar portions of ether or aceto~ae, sucked dry on the funnel, and air-dried. The yield of the desired salt is 20 g or 61 per cent based on the starting complex. The small amount of contaminating NaNO2 and NaC1 are removed in converting to the nitratO 2~ and the resulting compound gives no chloride test with silver nitrate. Electrolytic analysis for cobalt gave values of 17.5 and 17.7 per cent (theory 17.6 per cent). The qualitative test for the eis-isomer described by HOLTZCLAWt2~ confirmed that the product was the correct isomer, as did infra-red analysis. As a final check, the compound was resolved according to the method of Dvcv~Rt3~ and the specific rotation of the bromide salt found to be --0"45 ° (reported, --0-44°). It was found that allowing the diastereoisomer to stand in ice water for 2 hr rather than 10 min was advisable in order to obtain the expected yield. E. P. HARBULAK*
University of Detroit
M . J . ALBINAKI"
* Present address: General Electric Co., Large Lamp Division, Cleveland, Ohio. 1" Present address: Owens-Illinois Glass Co., Technical Center, Toledo, Ohio. c1~A. WARNER,Ber. 34, 1706 (1901) c*>H. F. HOLTZCLAW,D. P. SHEETYand B. D. MCCARTY, Inorganic Synth. IV, p. 176, McGraw-Hill, New York, 1953. ta~ F. P. DWYER and F. L. GARVAN, Inorganic Synth. VI, p. 192, McGraw-Hill, New York, 1960. t4~ j. C. BAILARJr., Inorganic Synth. I1, p. 223, McGraw-Hill, New York, 1946.
The direct determination of the normal boiling point of tin ¢1) (Received 3 August 1962) IN our studies on the density of liquid metals from their melting points to their normal boiling points, it was essential to know the normal boiling points of the metals. A literature search showed that the most reliable values for tin were those reported in the review literature by STULLand SINKE(2960°K) ~2~ and BREWER(3000°K). TM W h i l e determining the density of liquid tin c4~, it was observed that the tin actually boiled at 760 mm Hg, about 200 ° below the above literature values. To check this observation 250 g of tin (99-90~ ~1) This work was supported by the National Science Foundation under Grant 18829. c~ D. R. STULLand G. C. SIN~:E,Thermodynamic Properties of the Elements, Advances in Chemistry Series 18, American Chemical Society, Washington, D.C. 1956, p. 33. c8~ L. BREWER, Paper 3, Thermodynamic and Physical Properties of the Elements, p. 31 in: The Chemistry and Metallurgy of Miscellaneous Materials: Thermodynamics, L. L. QUILL, Editor, Vol. IV-19B, National Nuclear Energy Series, New York, McGraw-Hill, 1950. ~4~A. D. KmSn~NaAUM and J. A. CAMEL, Trans. Quart. Amer. Soe. Metall., 55, 844 (1962).
Letters to the editors
233
purity) were refluxed in a graphite crucible and reflux condenser under argon in the carbon tube furnace. Two calibrated p y r o " optical pyrometers ~ were used in these measurements. They were sighted into a black body cavity immersed into both the boiling liquid tin and its vapour. The tin boiled at 2780 ± 20°K at 760 m m Hg. The electrical imput of the furnace (18.0 kW.) was increased by 300 watts. This resulted in an increase in furnace temperature but not in the temperature o f the vapour or the boiling tin, which only boiled more vigorously. Since the observed boiling point was approximately 200 ° lower than the best values reported in the review literature, the same pyrometers were used as a check to determine the boiling and melting points o f various metals under the same conditions used for boiling tin. The results obtained are tabulated in Table 1. They are in good agreement, within the experimental error, of the best values reported in the literature except for tin. TABLE 1.--OBSERVED NORMAL BOILING AND MELTING POINTS OF VARIOUS METALS
Observed M.P. (°K) N.B.P. (°K)
Metal
Purity
Bi Sb Pb Pt In Ag Nb
99.95 100"0 99.99 99"99 99.97+ 99.99"99"85
---2040 ± l f f --2710 ± 2 0
1816 ~ 15 ~ 1907 ± 10 ° 2022 A: 10 ° -2285 :~- 15 ~ 2468 ÷ 15 ~ --
Cu Sn
99.95 99.90
---
28ll ± 20 ° 2780 ± 20 °
Best literature value, °K. 1832 '~'~ 1910 °~1°~ 2024 °~°~ 2046"7 -!: 0"2 °l~l 2273 ± 10 °(71 2450 °l~°~ 2770 ± 20 °18) 2741 ± 10 °l°l ave =- 2755 ± 20 ° 2855 °11°) 2960 °l~l 3000°lal
STtJCL and SINKE calculated the boiling points of Sn by applying the Second and Third Laws o f Thermodynamics to the vapour pressure data reported by BREWER and PORTERmj and SEARCY and FREEtC,AN~12)in the 10 -6 and 10 -4 atm. range. They assumed, in their calculations o f the boiling point of tin, that the tin vapour is monatomic since HONIG (131 showed mass spectrometricaIly that tin vapour is about 99 ~ monatomic while SEARCY and FREEMANfound that the molecular weight o f the vapour was 91 ×- 29. If this is true at a pressure o f 10 -" to 10 -4 atm., it is not necessarily so at a pressure of one atmosphere. The boiling point reported by STULL and SINKE is based on a long extrapolation o f BREWER and PORTER'S~11~and SEARCHand FREEMAN'S~12~vapour pressure data using a constant liquid heat capacity o f 7.3 cal mole -* deg.-L If a heat capacity of 6.0 cal mole -* deg. -1 was used, STULLC17~calculated the boiling points obtained from BREWER and PORTER'S and SEARCV and FREE~AN'S data to be 2787°K and 2837°K respectively. Thus, the discrepancy between the boiling point observed by the authors and those reported by SruLI, and SINKE~2~ and BREWER~8~ may be due to the liquid Cp value and/or the existence o f complex vapour species. It would be desirable to determine directly the normal boiling points of the homologs of tin, namely germanium and silicon, especially since HONI~ ~m has shown that Ge and Si vapours contain t~ Checked with the tungsten ribbon lamp at 2300 and 2500°K by The Pyrometer Instrument Company, Bergenfield, N.J. ~') W. F. ROESErq F. R. CALDWELL and H. T. WENSEL, Bur. Stand. J. Res. 6, 1119 (1931). t7) E. J. KOHLMEYER and H. SPANDAU,Z. Anorg. Chem. 253, 37 (1945). Cs~A. L. R~EMAN and C. K. GRANT, Phil. Mag. 22, 34 (1936). " H. T. SCHOFIELD, Inst. Metals J. 85, 372 (1957). ~10~D. R. STULL and G. C. S~NKE. Thermodynamic Properties of the Elements in Advances in Chemistry Series 18, American Chemical Society, Washington, D.C. 1956. pp. I0, 12, 16, 21, 30 (B.P. calculated from best vapour pressure, heats o f sublimation and vapouration data reported in the literature and should be accurate to --+20°). ¢11~L. BREWER and R. F. PORTER, J. Chem. Phys. 21, 2012 (1953". ¢~2, A. W. SEARCY and R. D. FREEMAN, 3". Amer. Chem. Soc. 76, 5229 (1954). cxa) R. E. HONIG, J. Chem. Phys, 21, 573 (1953). ¢x4) R. E. HONIG, J. Chem. Phys. 22, 1610 (1954).
234
Letters to the editors
mono, di, tri and tetratomic species and the literature shows a great disagreement as to the normal boiling point of Si la1,l~,lS,ae~ The value varies from 2625°K to 2950°K. A. D. KIRSHENBAUM Research Institute of Temple University J . A . CAHILL 4150 Henry Avenue Philadelphia 44, Pa, Cl~ E. BAUR and R, BRUNNER,Helv. Chim. Acta 17, 958 (1934). ~1~ O. RUFF and M. KONSCHAK,Z. Elektrochem. 32, 68 (1926). (171 n . R. STULL, Private communication.
Reagent dependence in sodium and strontium extraction by di(2-ethylhexyl) phosphoric acid (Received 27 September 1962) RECENT investigations here into the chemistry of strontium extraction from sodium nitrate solutions by di(2-ethylhexyl)-phosphoric acid (HX) in benzene indicate that the dependence of the extraction coefficient, E~t = (M)org/(M)aq, on HX concentration is direct second power when M = Na and direct third power when M = Sr if the aqueous pH (and therefore the amount of metal extracted) is low enough so that essentially all the extractant may be considered to be in the acid form. This latter case is in accord with the third power reagent dependence for calcium extraction from weak HC1 solutions by xylene solutions of di(2-ethylhexyl)phosphoric acid recently reported by PEPPARO et aL, ~1~who conjectured that strontium should also exhibit third-power reagent dependence. As HX in non-polar diluents is known to be a dimer, (HX)z c~ and since hydrogen-ion dependence for the extraction of these two metals by (HX)2 was also shown to be inverse first power in the case of sodium and inverse second power in the case of strontium, the following reactions are suggested Na + + 2(HX)2 ~ NaX'3HX + H + and Sr 2+ + 3(HX)~ ~ SrXf4HX + 2H +. These reactions may be generalized as: M l+ + (n/2) (HX)~ ~ MXi" (n -- i)HX + i H +. This is essentially the same as the reaction written by PEPPAgD,c1~ the difference being that no special significance is given to hydrogen bonding between ligands within the complex.* PEPPARD et al. previously explained discrepancies between [H +] dependence and reagent dependence in a series of metal extractions where the indicated stoichiometry was always M(X2H)n by proposing the single ionization of the acid dimer (HX)2, viz., (HX)2 ~ HX2- + H +, followed by chelation with the metal, c3) This adequately fitted the data and thus supported the view that chelation by hydrogen-bonded ligand pairs was of primary importance. It appears now, however, that satisfying the coordination number of the metal may be more important. The earlier data are generally consistent with this view as well as with the previous view, since in most reported c3,4) cases the accepted coordination number was twice the cation valence.t * Bonds between active hydrogens on the un-ionized molecules and phosphoryl oxygens on those which have formed the salt probably do occur at least to some extent. +, Exceptions are the cases of uranium(VI) reported by BhES, ZINGARO and COLEMANand by DYRSSEN and KRASOWC, and thorium(IV) reported by PEPPARD, MASON and McCARTY, accepted coordination number of 8. Using the model proposed here, a coordination number of 6 is required for both uranium and thorium (counting the uranyl oxygens in the case of uranium). In the case of Cm(III) and Cf(III) reported by PEPPARD, MASONand HUcHrR not enough is known of the coordination chemistry of these elements to state the usual coordination number. tl) D. F. PEPPARD,G. W. MASON,S. MCCARTYand F. D. JOHNSON,J. Inorg. Nucl. Chem., 24, 321-332 (1962). t2~ C. F. BAES,Jr., RALPH A. ZINGAROand C. F. COLEMAN,J. Phys. Chem. 62, 129 (1958). t3) D. F. PEPPARD, G. W. MASON,W. J. DRISCOLLand R. J. SIRONEN,J. Inorff. Nucl. Chem., 7, 276--258 (1958); D. F. PEPPARD, G. W. MASONand I. HocI-IER, J. Inorg. Nucl. Chem., 18, 245-258 (1961). t4) DAVID DYRSSEN, Acta Chem. Scand., 11, 1277-78 (1957); D. DYRSSENand F. KRASOVEC,Acta Chem. Scand., 13, 561-570 (1959); C. F. BAES,Jr., and H. T. BAKER,J. Phys. Chem., 64, 89 (1960); D. F. PEPPARD, G. W. MASON, J. L. MAIER and W. J. DRISCOLL,J. Inorg. Nucl. Chem., 4, 334 (1957); D. F. P~PPARD, G. W. MASON,and S. MCCARTY,J. Inorg. Nucl. Chem., 13, 138-150 (1960).
Letters to the editors
Preparation of
cis-dinitrobis(ethylenediamine)eobalt(III)
nitrite
(Received 13 August 1962) S~VERAL preparations of salts of the [Co(en),(NO2)2] + ion have been reported in the literature. The most usual is that of WERNER~1> as modified by HOLTZCLAW et al., c~ beginning with potassium hexanitroeobaltate. However, this method has several disadvantages including a starting material which is difficult to prepare in high purity and to dry thoroughly; critical temperature control; and low yield (12-15 per cent). Since the compound is not only interesting in its own right, being stable and resolvable, but is also the resolving agent recently applied most successfully to the resolution of the ethylene-dinitrilotetraacetatocobaltate ion, TM a simpler synthesis is desirable. A method using trans-dichlorobis(ethylenediamine)cobalt(III) chloride requires a much shorter time and is at least twice as efficient. EXPERIMENTAL Thirty grams of trans-dichlorobis(ethylenediamine)cobalt(III) chloride 14~ are dissolved with magnetic stirring in 150 ml cold H20. When the salt is dissolved, the solution is cooled to about --12 ° in an ice-salt bath and 114 g of powdered NaNO, added over 1 or 2 min while stirring fairly rapidly. The solution changes from green to red and before all the salt has been added is bright orange-brown with the suspension of the desired cis-salt. The mixture is cooled and stirred 30 min longer, filtered quickly, the precipitate washed once with 20-30 ml of cold water, twice with 20-30 ml portions of absolute ethanol, and twice with similar portions of ether or aceto~ae, sucked dry on the funnel, and air-dried. The yield of the desired salt is 20 g or 61 per cent based on the starting complex. The small amount of contaminating NaNO2 and NaC1 are removed in converting to the nitratO 2~ and the resulting compound gives no chloride test with silver nitrate. Electrolytic analysis for cobalt gave values of 17.5 and 17.7 per cent (theory 17.6 per cent). The qualitative test for the eis-isomer described by HOLTZCLAWt2~ confirmed that the product was the correct isomer, as did infra-red analysis. As a final check, the compound was resolved according to the method of Dvcv~Rt3~ and the specific rotation of the bromide salt found to be --0"45 ° (reported, --0-44°). It was found that allowing the diastereoisomer to stand in ice water for 2 hr rather than 10 min was advisable in order to obtain the expected yield. E. P. HARBULAK*
University of Detroit
M . J . ALBINAKI"
* Present address: General Electric Co., Large Lamp Division, Cleveland, Ohio. 1" Present address: Owens-Illinois Glass Co., Technical Center, Toledo, Ohio. c1~A. WARNER,Ber. 34, 1706 (1901) c*>H. F. HOLTZCLAW,D. P. SHEETYand B. D. MCCARTY, Inorganic Synth. IV, p. 176, McGraw-Hill, New York, 1953. ta~ F. P. DWYER and F. L. GARVAN, Inorganic Synth. VI, p. 192, McGraw-Hill, New York, 1960. t4~ j. C. BAILARJr., Inorganic Synth. I1, p. 223, McGraw-Hill, New York, 1946.
The direct determination of the normal boiling point of tin ¢1) (Received 3 August 1962) IN our studies on the density of liquid metals from their melting points to their normal boiling points, it was essential to know the normal boiling points of the metals. A literature search showed that the most reliable values for tin were those reported in the review literature by STULLand SINKE(2960°K) ~2~ and BREWER(3000°K). TM W h i l e determining the density of liquid tin c4~, it was observed that the tin actually boiled at 760 mm Hg, about 200 ° below the above literature values. To check this observation 250 g of tin (99-90~ ~1) This work was supported by the National Science Foundation under Grant 18829. c~ D. R. STULLand G. C. SIN~:E,Thermodynamic Properties of the Elements, Advances in Chemistry Series 18, American Chemical Society, Washington, D.C. 1956, p. 33. c8~ L. BREWER, Paper 3, Thermodynamic and Physical Properties of the Elements, p. 31 in: The Chemistry and Metallurgy of Miscellaneous Materials: Thermodynamics, L. L. QUILL, Editor, Vol. IV-19B, National Nuclear Energy Series, New York, McGraw-Hill, 1950. ~4~A. D. KmSn~NaAUM and J. A. CAMEL, Trans. Quart. Amer. Soe. Metall., 55, 844 (1962).
Letters to the editors
233
purity) were refluxed in a graphite crucible and reflux condenser under argon in the carbon tube furnace. Two calibrated p y r o " optical pyrometers ~ were used in these measurements. They were sighted into a black body cavity immersed into both the boiling liquid tin and its vapour. The tin boiled at 2780 ± 20°K at 760 m m Hg. The electrical imput of the furnace (18.0 kW.) was increased by 300 watts. This resulted in an increase in furnace temperature but not in the temperature o f the vapour or the boiling tin, which only boiled more vigorously. Since the observed boiling point was approximately 200 ° lower than the best values reported in the review literature, the same pyrometers were used as a check to determine the boiling and melting points o f various metals under the same conditions used for boiling tin. The results obtained are tabulated in Table 1. They are in good agreement, within the experimental error, of the best values reported in the literature except for tin. TABLE 1.--OBSERVED NORMAL BOILING AND MELTING POINTS OF VARIOUS METALS
Observed M.P. (°K) N.B.P. (°K)
Metal
Purity
Bi Sb Pb Pt In Ag Nb
99.95 100"0 99.99 99"99 99.97+ 99.99"99"85
---2040 ± l f f --2710 ± 2 0
1816 ~ 15 ~ 1907 ± 10 ° 2022 A: 10 ° -2285 :~- 15 ~ 2468 ÷ 15 ~ --
Cu Sn
99.95 99.90
---
28ll ± 20 ° 2780 ± 20 °
Best literature value, °K. 1832 '~'~ 1910 °~1°~ 2024 °~°~ 2046"7 -!: 0"2 °l~l 2273 ± 10 °(71 2450 °l~°~ 2770 ± 20 °18) 2741 ± 10 °l°l ave =- 2755 ± 20 ° 2855 °11°) 2960 °l~l 3000°lal
STtJCL and SINKE calculated the boiling points of Sn by applying the Second and Third Laws o f Thermodynamics to the vapour pressure data reported by BREWER and PORTERmj and SEARCY and FREEtC,AN~12)in the 10 -6 and 10 -4 atm. range. They assumed, in their calculations o f the boiling point of tin, that the tin vapour is monatomic since HONIG (131 showed mass spectrometricaIly that tin vapour is about 99 ~ monatomic while SEARCY and FREEMANfound that the molecular weight o f the vapour was 91 ×- 29. If this is true at a pressure o f 10 -" to 10 -4 atm., it is not necessarily so at a pressure of one atmosphere. The boiling point reported by STULL and SINKE is based on a long extrapolation o f BREWER and PORTER'S~11~and SEARCHand FREEMAN'S~12~vapour pressure data using a constant liquid heat capacity o f 7.3 cal mole -* deg.-L If a heat capacity of 6.0 cal mole -* deg. -1 was used, STULLC17~calculated the boiling points obtained from BREWER and PORTER'S and SEARCV and FREE~AN'S data to be 2787°K and 2837°K respectively. Thus, the discrepancy between the boiling point observed by the authors and those reported by SruLI, and SINKE~2~ and BREWER~8~ may be due to the liquid Cp value and/or the existence o f complex vapour species. It would be desirable to determine directly the normal boiling points of the homologs of tin, namely germanium and silicon, especially since HONI~ ~m has shown that Ge and Si vapours contain t~ Checked with the tungsten ribbon lamp at 2300 and 2500°K by The Pyrometer Instrument Company, Bergenfield, N.J. ~') W. F. ROESErq F. R. CALDWELL and H. T. WENSEL, Bur. Stand. J. Res. 6, 1119 (1931). t7) E. J. KOHLMEYER and H. SPANDAU,Z. Anorg. Chem. 253, 37 (1945). Cs~A. L. R~EMAN and C. K. GRANT, Phil. Mag. 22, 34 (1936). " H. T. SCHOFIELD, Inst. Metals J. 85, 372 (1957). ~10~D. R. STULL and G. C. S~NKE. Thermodynamic Properties of the Elements in Advances in Chemistry Series 18, American Chemical Society, Washington, D.C. 1956. pp. I0, 12, 16, 21, 30 (B.P. calculated from best vapour pressure, heats o f sublimation and vapouration data reported in the literature and should be accurate to --+20°). ¢11~L. BREWER and R. F. PORTER, J. Chem. Phys. 21, 2012 (1953". ¢~2, A. W. SEARCY and R. D. FREEMAN, 3". Amer. Chem. Soc. 76, 5229 (1954). cxa) R. E. HONIG, J. Chem. Phys, 21, 573 (1953). ¢x4) R. E. HONIG, J. Chem. Phys. 22, 1610 (1954).
234
Letters to the editors
mono, di, tri and tetratomic species and the literature shows a great disagreement as to the normal boiling point of Si la1,l~,lS,ae~ The value varies from 2625°K to 2950°K. A. D. KIRSHENBAUM Research Institute of Temple University J . A . CAHILL 4150 Henry Avenue Philadelphia 44, Pa, Cl~ E. BAUR and R, BRUNNER,Helv. Chim. Acta 17, 958 (1934). ~1~ O. RUFF and M. KONSCHAK,Z. Elektrochem. 32, 68 (1926). (171 n . R. STULL, Private communication.
Reagent dependence in sodium and strontium extraction by di(2-ethylhexyl) phosphoric acid (Received 27 September 1962) RECENT investigations here into the chemistry of strontium extraction from sodium nitrate solutions by di(2-ethylhexyl)-phosphoric acid (HX) in benzene indicate that the dependence of the extraction coefficient, E~t = (M)org/(M)aq, on HX concentration is direct second power when M = Na and direct third power when M = Sr if the aqueous pH (and therefore the amount of metal extracted) is low enough so that essentially all the extractant may be considered to be in the acid form. This latter case is in accord with the third power reagent dependence for calcium extraction from weak HC1 solutions by xylene solutions of di(2-ethylhexyl)phosphoric acid recently reported by PEPPARO et aL, ~1~who conjectured that strontium should also exhibit third-power reagent dependence. As HX in non-polar diluents is known to be a dimer, (HX)z c~ and since hydrogen-ion dependence for the extraction of these two metals by (HX)2 was also shown to be inverse first power in the case of sodium and inverse second power in the case of strontium, the following reactions are suggested Na + + 2(HX)2 ~ NaX'3HX + H + and Sr 2+ + 3(HX)~ ~ SrXf4HX + 2H +. These reactions may be generalized as: M l+ + (n/2) (HX)~ ~ MXi" (n -- i)HX + i H +. This is essentially the same as the reaction written by PEPPAgD,c1~ the difference being that no special significance is given to hydrogen bonding between ligands within the complex.* PEPPARD et al. previously explained discrepancies between [H +] dependence and reagent dependence in a series of metal extractions where the indicated stoichiometry was always M(X2H)n by proposing the single ionization of the acid dimer (HX)2, viz., (HX)2 ~ HX2- + H +, followed by chelation with the metal, c3) This adequately fitted the data and thus supported the view that chelation by hydrogen-bonded ligand pairs was of primary importance. It appears now, however, that satisfying the coordination number of the metal may be more important. The earlier data are generally consistent with this view as well as with the previous view, since in most reported c3,4) cases the accepted coordination number was twice the cation valence.t * Bonds between active hydrogens on the un-ionized molecules and phosphoryl oxygens on those which have formed the salt probably do occur at least to some extent. +, Exceptions are the cases of uranium(VI) reported by BhES, ZINGARO and COLEMANand by DYRSSEN and KRASOWC, and thorium(IV) reported by PEPPARD, MASON and McCARTY, accepted coordination number of 8. Using the model proposed here, a coordination number of 6 is required for both uranium and thorium (counting the uranyl oxygens in the case of uranium). In the case of Cm(III) and Cf(III) reported by PEPPARD, MASONand HUcHrR not enough is known of the coordination chemistry of these elements to state the usual coordination number. tl) D. F. PEPPARD,G. W. MASON,S. MCCARTYand F. D. JOHNSON,J. Inorg. Nucl. Chem., 24, 321-332 (1962). t2~ C. F. BAES,Jr., RALPH A. ZINGAROand C. F. COLEMAN,J. Phys. Chem. 62, 129 (1958). t3) D. F. PEPPARD, G. W. MASON,W. J. DRISCOLLand R. J. SIRONEN,J. Inorff. Nucl. Chem., 7, 276--258 (1958); D. F. PEPPARD, G. W. MASONand I. HocI-IER, J. Inorg. Nucl. Chem., 18, 245-258 (1961). t4) DAVID DYRSSEN, Acta Chem. Scand., 11, 1277-78 (1957); D. DYRSSENand F. KRASOVEC,Acta Chem. Scand., 13, 561-570 (1959); C. F. BAES,Jr., and H. T. BAKER,J. Phys. Chem., 64, 89 (1960); D. F. PEPPARD, G. W. MASON, J. L. MAIER and W. J. DRISCOLL,J. Inorg. Nucl. Chem., 4, 334 (1957); D. F. P~PPARD, G. W. MASON,and S. MCCARTY,J. Inorg. Nucl. Chem., 13, 138-150 (1960).