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Enrichment of deuterium with tritium in the presence of a palladium-561 giant cluster
Journal
of Molecular
Catal@s,
66 (1991)
99-104
99
Enrichment of deuterium with tritium in the presence of a palladium-56 1 giant cluster D. I. Kochubey’, V. P. Babenko Institute of Catalysis, Siberian Novosibirsk 630090 (U.S.S.R.)
Branch
of the U.S.S.R. Acad.em~
of Sciences,
M. N. Vargaftik and I. I. Moiseev* N. S. Kurnakov Institute of General Sciences, Moscow 117907 (U.S.S.R.)
and Inorganic
Chemistv,
the U.S.S.R. Academy
of
(Received June 26, 1990; revised December 12, 1990)
Abstract In experiments where a pahadium giant cluster of PdssiPhen,&OAc)is,, idealized formula was contacted with gaseous deuterium at room temperature and atmospheric pressure, the content of tritium in deuterium was increased. Among various origins of the effect observed, deuteron-deuteron cold fusion is considered.
Introduction The palladium giant cluster of idealized formula PdseIPheneo(OAc)lso (1) (Phen = l,lO-phenanthroline) was recently found to be the effective catalyst for various liquid-phase oxidative reactions [ 11. The cluster was characterized by high-resolution transmission electron microscopy, small-angle X-ray scattering, EXAFS and NMR spectroscopy, magnetic succeptibility, molecular mass and chemical analysis data [ 1, 21. On the basis of these data, the substance was found to consist of uniform particles with a massive, denselypacked Pd5T0i3~ metal core 26 + 5 A in diameter, bonded with 63 +3 Phen molecules and surrounded by 190 L-10 OAc- ligands at its periphery. Palladium atoms are packed within the core as multi-layer icosahedra (in an idealized model, five-layer polyhedra consisting of 561 Pd atoms) with 10 to 12 metal atoms along the maximal diameter of the metal core. The substance was found to absorb up to one hydrogen atom per Pd atom from gaseous Ha at room temperature and atmospheric pressure. The hydrogen absorbed can be removed in vacua or by the action of gaseous oxygen, in the latter case forming water. Absorption and removal processes were repeated several times without substantial change in the hydrogen absorption of each cycle. This study was prompted by the experiments of Fleischmann and Pons [ 31 and Jones et al. [ 41 on cold d-d nuclear fusion with palladium electrodes. *Authors to whom correspondence should be addressed.
0304-5102/91/$3.50
0 Elsevier Sequoia/Printed in The Netherlands
In the discussions on possible origins of the effects declared, mechanicoelectrical phenomena due to the fracture of metal (or its deuteride) crystal lattice were suggested to be the plausible origin of the effects mentioned [5]. Strong local electric fields at the propagation crack were presumed to induce d-d fusion [ 61. When bulk palladium metal is saturated with deuterium or hydrogen, a solid material could undergo cracking because of the considerable difference between the crystal lattice constants of the metal and its deuteride (hydride). Palladium black as well as colloidal palladium are known to possess a wide size distribution, including a substantial portion of large crystallites on a micron scale. In these cases, mechanico-electrical effects accompanying the absorption of deuterium or hydrogen by palladium could not be excluded. To eliminate the above effects, we have studied gaseous Dz contacted with palladium in the form of giant cluster 1.The cores of cluster 1 molecules being very small and uniformly distributed, the phenomena observed in the experiments were expected not to be affected by any cracking effects.
Experimental Materials Cluster 1 was obtained by successive treatment of Pd(OAc), with Ha and O2 in acetic acid solution contained Phen as described in [ 11. Pd(I1) acetate was prepared by oxidation of palladium black with HNOa using the procedure described in [7]. Gaseous deuterium was prepared by the reaction of pure deuterium oxide with metallic sodium and was stored in a gas burette under dibutyl phthalate as a lock liquid. The admixture of tritium in D20 used was characterized by counting rates equal to 50 counts min-’ cmW3 of DzO. Experimental procedure The experimental set-up is shown in Fig. 1. Samples of cluster 1 were 1.5 to 2.0 g (corresponding to 1.2 to 1.5 g of palladium) in variousexperimental runs. Before each run, the gas burette was blown thoroughly with dry Ar. A sample of palladium cluster was also blown with dry Ar or evacuated to 10e2 torr at 20 “C before each run. Gaseous deuterium was brought into contact with a sample of palladium cluster at room temperature and atmospheric pressure during 1 to 11 days, after which the gas was removed from the reaction vessel by Ar flow. The D2-Ar mixture with oxygen added was passed over Pt/A1203 catalyst at 200 “C to convert Dz into D20. Deuterium oxide obtained was collected in a cold trap at - 70 “C and then placed into the cuvette of a dioxane scintillator (81. Background counting rates of the cuvette were preliminarily measured. The amount of tritium was registered with a liquid scintillator counter SL4221 (Roche Bioelectronic). Each recorded run included at least 10 mea-
101
Fig. 1. Schematic diagram of the experimental apparatus: (1) valve, (2) gas burette of 400 cm3 volume under dibutyl phthalate, (3) reaction vessel, (4) Pt/A1203 catalyst for conversion of D,+O, to D,O, (5) D,O collector.
surements of 2 min duration, with suppression of chemihuninescence, and using an external standard. The background of cuvette and tritium content were measured using the correction on quenching, which was constant (94-96%) for all the runs. Cuvette background was found to be’ constant over at least 10 days. The mean divergence of counting rates was equal to f10 counts mm-’ for alI runs. The experimental procedure used did not permit complete collection of all the deuterium after its contact with the palladium cluster. Some amounts of DzO vapour were carried away from the trap by the gas flow. From 10 to 60% of the total Dz was collected in the experiments. Results
and discussion
Experimental
results
The experimental data for the runs in which Dz was contacted with a freshly-prepared sample of cluster 1 are given in Table 1. The observed values of counting rates exceeded those for the background as well as for the expected upper limit for possible tritium admixture transferred from the initial heavy water (see below). The effect observed was proved to be connected with the contact of deuterium with the palladium cluster. Table 2 shows the results of the series of experiments in which the run with Dz was followed by contact of the cluster with Hz and vice versa. In the first series of rims, Hz was contacted with a fresh sample of the cluster. As is seen from Table ‘2, no excess
102 TABLE 1 Tritium observation in experiments with Da contacted with freshly-prepared palladium cluster samples Contact time (days)
DsO collected W)
Cuvette background (counts mm-‘)
counting rates (counts mm-‘)
A, 3H decay rates (counts min-‘)
3H decay rates for 1 cm3 Da0 (counts mm’)
5 5 11
44 18 70
166 144 162
290 226 820
124 82 658
2800 4500 9400
TABLE 2 Tritium observed in experiments with Ds and Ha contacted with palladium cluster in diierent sequences Contact time (days)
DsO collected (0)
Cuvette background (counts min-‘)
counting rates (counts min-‘)
Hz without 5
con&& 80
with Pd cluster 162
170
H, contacted
with fresh Pd cluster 55 166
169
6
Hz contacted with Pd cluster 5 26 169 3 90 160
1
110
161
Dz contacted with Pd cluster 9 64 166 5 154 138 6 110 162
5 6 5 6
104 76 130 100
previously
149 168 165 166
contacted 246 241
180 previously
contacted 208 173
214 215 245 251 180
A, 3H decay rates (counts mm-‘)
3H decay rates for 1 cm3 DsO (counts min-‘)
8 3 with Dz 77 81
3000 800
19
170
with Hz 42 35
52 66 77 86 14
620 230 470 670
1000 660 340
counting rates above background were found in this case. In the second series, Hz was contacted with the cluster sample used earlier in the rtms with deuterium. Some excess tritium content above background was found in this series, suggesting that the removal of tritium from the palladium cluster at 10e2 torr and 20 “C after the preceding experimental run was not effective. The experiments in which D2 was contacted with the cluster after its use in the runs with H2 yielded lower quantities of tritium than those with
103
a fresh sample of the chister. In subsequent runs with Dz the yields of tritium slightly increased. Possible origins of tritium In the basic experiments, some quantities of tritium or any radiation species from the initial heavy water (used for preparation of gaseous deuterium), metallic sodium, dibutyl phthalate or Pt/A120a catalyst, as well as from the walls of the apparatus could be retained by deuterium. The upper limit of possible tritium content in the final heavy water (obtained by the oxidation of total amount of Da taken in the experimental run) was estimated as 32 counts min-‘, assuming complete transfer of tritium from the initial heavy water to the final one. The real value is obviously less than this. Dibutyl phthalate is known to be a powerful radiation quencher and its vapour could not increase the counting rates. Two types of blank experiments were carried out to estimate the real contribution of other possible admixtures: (1) Gaseous Dz, prepared using the same samples of initial D20 and sodium metal as those in the basic experiments, was oxidized with the same Pt/Al,O, catalyst without contact with palladium cluster. The counting rates for the D20 obtained was found to coincide with those for cuvette background, within experimental error. (2) Gaseous Hz, with initial background counting rates equal to 14 counts min-’ per 100 cm3 (corresponding to 170 counts min-’ cmW3 of HaO), was contacted with the palladium cluster over 5 days and then was converted to water using the same procedure as in the basic experiments. The collected water showed the same counting rates as the background. The enhanced tritium content in the final heavy water could be assumed to have transferred from the Phen and OAc- ligands of the cluster to gaseous D2 due to isotopic exchange catalysed by the cluster (the tritium content in the hydrogen atoms of the ligands was unknown). However, this assumption is inconsistent with the results of the experiments in which Ha was used instead of Dz. In the runs in which Ha was contacted for 5 days with freshlyprepared palladium cluster, the collected water exhibited counting rates identical with those for the background (see Table 2). Lastly, yet another origin of the enhanced tritium observations could be presumed to be selective absorption of D2 by cluster 1 due to a high D2/Ta isotopic effect. Thus, a considerable decrease in gas volume, of the order of 100 cm3, caused by absorption of deuterium by the cluster, was observed at the beginning of each experimental run. If deuterium was absorbed preferably in comparison with tritium, the gas phase would be somewhat enriched with the latter. However, even in this case the total amount of tritium found in the final heavy water should not exceed that contained in the initial one (the upper limit was estimated as 32 counts min-‘, see above). As is seen from the fifth column of Table 1, the counting rates found in the experiments exceed thisvalue by 2.5 to 20 times. Therefore, this assumption also cannot explain the origin of the enhanced tritium observations.
104
Conclusions
The obtained data show that the tritium content in gaseous deuteriurn was increased after its contact with the palladium giant cluster 1 at room temperature and atmospheric pressure for 5-10 days. Additional experiments need to be carried out prior to definite judgements on the nature of this effect. I t should be noted that the effect was observed in the absence of both electrolysis and possible crack phenomena discussed in the context of the papers [ 3-61.
Acknowledgements
The authors thank Dr. V. P. Zagorodnikov for preparation of the palladium cluster samples, Dr. V. A. Rogov for help in measurementsof tritium content, and Dr. V. N. Parmon, Professor K. I. Zamaraev, Professor M. E. Volpin and Professor H. D. Kaesz for useful discussions.
References 1 M. N. Vargaftik, V. P. Zagorodnikov, I. P. Stolyarov, I. I. Moiseev, D. I. Kochubey, V. A. Likholobov, A. L. Chuvilin and K. I. Zamaraev, J. Mol. Cutal., 53 (1989) 315. 2 M. N. Vargaftik, V. P. Zagorodnikov, I. P. Stolyarov, I. I. Moiseev, V. A. Likholobov, D. I. Kochubey, A. L. Chuvilin, V. I. Zaikovskii, K. I. Zamaraev and G. I. Tiofeeva, J. Chem. Sot., Chem. Commun., (1985) 937. 3 M. Fleischmann and S. Pons, J. EL&rocmaZ~t. Ch., 261 (1989) 301. 4 S. E. Jones, E. P. Palmer, J. B. C&r, D. L. Decker, G. L. Jensen, J. M. Thome, S. F. Taylor and J. Rafelski, Nature, 338 (1989) 737. 5 J. S. Kohen and J. D. Davies, Nature, 338 (1989) 705. 6 V. A. Klyuev, A. G. Lipson, Yu. P. Toporov, B. V. Deryaguin, V. I. Lustchikov, A. V. Strelkov and E. P. Shabalin, Sov. Tekh. P/zgs. L&t., I2 (1986) 551. 7 T. A. Stephenson, S. M. Morehouse, A. R. Powell, J. P. Heffer and G. W&son, J. Chem. Sot., (1965) 3632. 8 G. A. Bray, Anal. Bidmn., 1 (1960) 279.
of Molecular
Catal@s,
66 (1991)
99-104
99
Enrichment of deuterium with tritium in the presence of a palladium-56 1 giant cluster D. I. Kochubey’, V. P. Babenko Institute of Catalysis, Siberian Novosibirsk 630090 (U.S.S.R.)
Branch
of the U.S.S.R. Acad.em~
of Sciences,
M. N. Vargaftik and I. I. Moiseev* N. S. Kurnakov Institute of General Sciences, Moscow 117907 (U.S.S.R.)
and Inorganic
Chemistv,
the U.S.S.R. Academy
of
(Received June 26, 1990; revised December 12, 1990)
Abstract In experiments where a pahadium giant cluster of PdssiPhen,&OAc)is,, idealized formula was contacted with gaseous deuterium at room temperature and atmospheric pressure, the content of tritium in deuterium was increased. Among various origins of the effect observed, deuteron-deuteron cold fusion is considered.
Introduction The palladium giant cluster of idealized formula PdseIPheneo(OAc)lso (1) (Phen = l,lO-phenanthroline) was recently found to be the effective catalyst for various liquid-phase oxidative reactions [ 11. The cluster was characterized by high-resolution transmission electron microscopy, small-angle X-ray scattering, EXAFS and NMR spectroscopy, magnetic succeptibility, molecular mass and chemical analysis data [ 1, 21. On the basis of these data, the substance was found to consist of uniform particles with a massive, denselypacked Pd5T0i3~ metal core 26 + 5 A in diameter, bonded with 63 +3 Phen molecules and surrounded by 190 L-10 OAc- ligands at its periphery. Palladium atoms are packed within the core as multi-layer icosahedra (in an idealized model, five-layer polyhedra consisting of 561 Pd atoms) with 10 to 12 metal atoms along the maximal diameter of the metal core. The substance was found to absorb up to one hydrogen atom per Pd atom from gaseous Ha at room temperature and atmospheric pressure. The hydrogen absorbed can be removed in vacua or by the action of gaseous oxygen, in the latter case forming water. Absorption and removal processes were repeated several times without substantial change in the hydrogen absorption of each cycle. This study was prompted by the experiments of Fleischmann and Pons [ 31 and Jones et al. [ 41 on cold d-d nuclear fusion with palladium electrodes. *Authors to whom correspondence should be addressed.
0304-5102/91/$3.50
0 Elsevier Sequoia/Printed in The Netherlands
In the discussions on possible origins of the effects declared, mechanicoelectrical phenomena due to the fracture of metal (or its deuteride) crystal lattice were suggested to be the plausible origin of the effects mentioned [5]. Strong local electric fields at the propagation crack were presumed to induce d-d fusion [ 61. When bulk palladium metal is saturated with deuterium or hydrogen, a solid material could undergo cracking because of the considerable difference between the crystal lattice constants of the metal and its deuteride (hydride). Palladium black as well as colloidal palladium are known to possess a wide size distribution, including a substantial portion of large crystallites on a micron scale. In these cases, mechanico-electrical effects accompanying the absorption of deuterium or hydrogen by palladium could not be excluded. To eliminate the above effects, we have studied gaseous Dz contacted with palladium in the form of giant cluster 1.The cores of cluster 1 molecules being very small and uniformly distributed, the phenomena observed in the experiments were expected not to be affected by any cracking effects.
Experimental Materials Cluster 1 was obtained by successive treatment of Pd(OAc), with Ha and O2 in acetic acid solution contained Phen as described in [ 11. Pd(I1) acetate was prepared by oxidation of palladium black with HNOa using the procedure described in [7]. Gaseous deuterium was prepared by the reaction of pure deuterium oxide with metallic sodium and was stored in a gas burette under dibutyl phthalate as a lock liquid. The admixture of tritium in D20 used was characterized by counting rates equal to 50 counts min-’ cmW3 of DzO. Experimental procedure The experimental set-up is shown in Fig. 1. Samples of cluster 1 were 1.5 to 2.0 g (corresponding to 1.2 to 1.5 g of palladium) in variousexperimental runs. Before each run, the gas burette was blown thoroughly with dry Ar. A sample of palladium cluster was also blown with dry Ar or evacuated to 10e2 torr at 20 “C before each run. Gaseous deuterium was brought into contact with a sample of palladium cluster at room temperature and atmospheric pressure during 1 to 11 days, after which the gas was removed from the reaction vessel by Ar flow. The D2-Ar mixture with oxygen added was passed over Pt/A1203 catalyst at 200 “C to convert Dz into D20. Deuterium oxide obtained was collected in a cold trap at - 70 “C and then placed into the cuvette of a dioxane scintillator (81. Background counting rates of the cuvette were preliminarily measured. The amount of tritium was registered with a liquid scintillator counter SL4221 (Roche Bioelectronic). Each recorded run included at least 10 mea-
101
Fig. 1. Schematic diagram of the experimental apparatus: (1) valve, (2) gas burette of 400 cm3 volume under dibutyl phthalate, (3) reaction vessel, (4) Pt/A1203 catalyst for conversion of D,+O, to D,O, (5) D,O collector.
surements of 2 min duration, with suppression of chemihuninescence, and using an external standard. The background of cuvette and tritium content were measured using the correction on quenching, which was constant (94-96%) for all the runs. Cuvette background was found to be’ constant over at least 10 days. The mean divergence of counting rates was equal to f10 counts mm-’ for alI runs. The experimental procedure used did not permit complete collection of all the deuterium after its contact with the palladium cluster. Some amounts of DzO vapour were carried away from the trap by the gas flow. From 10 to 60% of the total Dz was collected in the experiments. Results
and discussion
Experimental
results
The experimental data for the runs in which Dz was contacted with a freshly-prepared sample of cluster 1 are given in Table 1. The observed values of counting rates exceeded those for the background as well as for the expected upper limit for possible tritium admixture transferred from the initial heavy water (see below). The effect observed was proved to be connected with the contact of deuterium with the palladium cluster. Table 2 shows the results of the series of experiments in which the run with Dz was followed by contact of the cluster with Hz and vice versa. In the first series of rims, Hz was contacted with a fresh sample of the cluster. As is seen from Table ‘2, no excess
102 TABLE 1 Tritium observation in experiments with Da contacted with freshly-prepared palladium cluster samples Contact time (days)
DsO collected W)
Cuvette background (counts mm-‘)
counting rates (counts mm-‘)
A, 3H decay rates (counts min-‘)
3H decay rates for 1 cm3 Da0 (counts mm’)
5 5 11
44 18 70
166 144 162
290 226 820
124 82 658
2800 4500 9400
TABLE 2 Tritium observed in experiments with Ds and Ha contacted with palladium cluster in diierent sequences Contact time (days)
DsO collected (0)
Cuvette background (counts min-‘)
counting rates (counts min-‘)
Hz without 5
con&& 80
with Pd cluster 162
170
H, contacted
with fresh Pd cluster 55 166
169
6
Hz contacted with Pd cluster 5 26 169 3 90 160
1
110
161
Dz contacted with Pd cluster 9 64 166 5 154 138 6 110 162
5 6 5 6
104 76 130 100
previously
149 168 165 166
contacted 246 241
180 previously
contacted 208 173
214 215 245 251 180
A, 3H decay rates (counts mm-‘)
3H decay rates for 1 cm3 DsO (counts min-‘)
8 3 with Dz 77 81
3000 800
19
170
with Hz 42 35
52 66 77 86 14
620 230 470 670
1000 660 340
counting rates above background were found in this case. In the second series, Hz was contacted with the cluster sample used earlier in the rtms with deuterium. Some excess tritium content above background was found in this series, suggesting that the removal of tritium from the palladium cluster at 10e2 torr and 20 “C after the preceding experimental run was not effective. The experiments in which D2 was contacted with the cluster after its use in the runs with H2 yielded lower quantities of tritium than those with
103
a fresh sample of the chister. In subsequent runs with Dz the yields of tritium slightly increased. Possible origins of tritium In the basic experiments, some quantities of tritium or any radiation species from the initial heavy water (used for preparation of gaseous deuterium), metallic sodium, dibutyl phthalate or Pt/A120a catalyst, as well as from the walls of the apparatus could be retained by deuterium. The upper limit of possible tritium content in the final heavy water (obtained by the oxidation of total amount of Da taken in the experimental run) was estimated as 32 counts min-‘, assuming complete transfer of tritium from the initial heavy water to the final one. The real value is obviously less than this. Dibutyl phthalate is known to be a powerful radiation quencher and its vapour could not increase the counting rates. Two types of blank experiments were carried out to estimate the real contribution of other possible admixtures: (1) Gaseous Dz, prepared using the same samples of initial D20 and sodium metal as those in the basic experiments, was oxidized with the same Pt/Al,O, catalyst without contact with palladium cluster. The counting rates for the D20 obtained was found to coincide with those for cuvette background, within experimental error. (2) Gaseous Hz, with initial background counting rates equal to 14 counts min-’ per 100 cm3 (corresponding to 170 counts min-’ cmW3 of HaO), was contacted with the palladium cluster over 5 days and then was converted to water using the same procedure as in the basic experiments. The collected water showed the same counting rates as the background. The enhanced tritium content in the final heavy water could be assumed to have transferred from the Phen and OAc- ligands of the cluster to gaseous D2 due to isotopic exchange catalysed by the cluster (the tritium content in the hydrogen atoms of the ligands was unknown). However, this assumption is inconsistent with the results of the experiments in which Ha was used instead of Dz. In the runs in which Ha was contacted for 5 days with freshlyprepared palladium cluster, the collected water exhibited counting rates identical with those for the background (see Table 2). Lastly, yet another origin of the enhanced tritium observations could be presumed to be selective absorption of D2 by cluster 1 due to a high D2/Ta isotopic effect. Thus, a considerable decrease in gas volume, of the order of 100 cm3, caused by absorption of deuterium by the cluster, was observed at the beginning of each experimental run. If deuterium was absorbed preferably in comparison with tritium, the gas phase would be somewhat enriched with the latter. However, even in this case the total amount of tritium found in the final heavy water should not exceed that contained in the initial one (the upper limit was estimated as 32 counts min-‘, see above). As is seen from the fifth column of Table 1, the counting rates found in the experiments exceed thisvalue by 2.5 to 20 times. Therefore, this assumption also cannot explain the origin of the enhanced tritium observations.
104
Conclusions
The obtained data show that the tritium content in gaseous deuteriurn was increased after its contact with the palladium giant cluster 1 at room temperature and atmospheric pressure for 5-10 days. Additional experiments need to be carried out prior to definite judgements on the nature of this effect. I t should be noted that the effect was observed in the absence of both electrolysis and possible crack phenomena discussed in the context of the papers [ 3-61.
Acknowledgements
The authors thank Dr. V. P. Zagorodnikov for preparation of the palladium cluster samples, Dr. V. A. Rogov for help in measurementsof tritium content, and Dr. V. N. Parmon, Professor K. I. Zamaraev, Professor M. E. Volpin and Professor H. D. Kaesz for useful discussions.
References 1 M. N. Vargaftik, V. P. Zagorodnikov, I. P. Stolyarov, I. I. Moiseev, D. I. Kochubey, V. A. Likholobov, A. L. Chuvilin and K. I. Zamaraev, J. Mol. Cutal., 53 (1989) 315. 2 M. N. Vargaftik, V. P. Zagorodnikov, I. P. Stolyarov, I. I. Moiseev, V. A. Likholobov, D. I. Kochubey, A. L. Chuvilin, V. I. Zaikovskii, K. I. Zamaraev and G. I. Tiofeeva, J. Chem. Sot., Chem. Commun., (1985) 937. 3 M. Fleischmann and S. Pons, J. EL&rocmaZ~t. Ch., 261 (1989) 301. 4 S. E. Jones, E. P. Palmer, J. B. C&r, D. L. Decker, G. L. Jensen, J. M. Thome, S. F. Taylor and J. Rafelski, Nature, 338 (1989) 737. 5 J. S. Kohen and J. D. Davies, Nature, 338 (1989) 705. 6 V. A. Klyuev, A. G. Lipson, Yu. P. Toporov, B. V. Deryaguin, V. I. Lustchikov, A. V. Strelkov and E. P. Shabalin, Sov. Tekh. P/zgs. L&t., I2 (1986) 551. 7 T. A. Stephenson, S. M. Morehouse, A. R. Powell, J. P. Heffer and G. W&son, J. Chem. Sot., (1965) 3632. 8 G. A. Bray, Anal. Bidmn., 1 (1960) 279.