The further absorpt,ion of hydrogen in tile b'phase may be visualized as occupation by hydrogtw of vacant lattice sites in the hydride lattice. If the sites are smaller than the hydrogen atmomso r ions, tJheentry of the 1at)t'erwould result in a distension of the lattice such as is observed in Fig. 1. $ 22 1 An alternate interpretat,ion, which agrees with other properties of the system, e.g., dissociation pressure, is that the vacancies attract one another more than do the hydrogens. The lattice energy of the defect structure is slightly higher and t'he lattice parameter slightly lower than that of the perfect structure. As hydrogens occupy ~ a c a n t , sites, therefore, the lattice expands. In contrast to palladium hydride, no contraction. of the uranium hydride lattice is observed at a fixed temperature when the hydrogen pressure is deL - 3.960 3.98QW 3.880 3.90CI 3.920 3.940 4.000 4.020 creased.9 The difference in behavior bet'ween LATTICE P A R A M E T E R , A . UH3 and PdH, may be due to the large difference Fig. 2. in the number of hydrogen vacancies t,hat the t x o The rmction occurring in the plateau region hydride lattices can tolerate. I n uranium hycan, if n~ neglect non-stoichiometry, be written dride the attractive energy between vacancies (E",) is 6.6 kcal./mole and the corresponding value 2Pd + Hz 2PdH for palladium hydride is about 2.1 kcal./mole.'4 The heat of this reaction, [ A H ] , then can be cal- Libowitz points out that the greater the value of culated from the integrated form of the van't E,,, the smaller the concentration of vacancies Hoff equation. A logarithmic plot of P tis. 1/T required to break down the 1 a t t i ~ e . I The ~ inusing the evo!!ut'ion plateau pressures from Table crease in concentration of vacancies when hydroI1 yields a st)ra,ightline and a value of -9.5 kcal./ gen is removed from uranium hydride presumably is TARLE I1 too small to produce an observable decrease in the PL.4TE.4U PRESSVFLES AT VARIOUS TEMPERATURES lattice parameter before the hydride phase breaks down. I n palladium hydride, however, the inTemp., " C . P)i/z, cm. U T x 103 creased concentration of vacancies is much larger 80 8.0 2.83 8 and the lattice parameter is observed to decrease 100 14.0 2.G8 8 (Fig. 1). I20 30.0 2.54 8
304
200 258 294 301
"9
709 1215 13%
2.09 1.88 1.76 1.i4
This This This This
work work work work
mole for A H . Kace and Aston recently reported - 9.G kcal./rriole from calorimetric absorption measiirements at 30°.12 Extrapolation of the data to the critical solution temperature (308') gives a yalue of 19.7 atm. for the critical solution pressure in ag:reement with the value reported by Gillespie and Galstaun (ref. 11). Above the critical t'emperature n homogeneous transition occurs between the cy- and the @-phase. Whether or not this transformation, requires a complex rearrangement cannot be as;serted, since the positions of the hydrogens in the a-phase have as yet not been established. Worsham,13 et al., have shown by neutron diffraction studies that the hydrogen atoms occupy octahedral sites in the face-centered cubic palladium lattice to give a NaCl type struct'ure. They mere unable to determine the hydrogen positions in the a-phase because of the very small hydrogen concentration in this phase a t room temperature. Extension of the neutron diffraction experiments to higher temperatures and pressures (higher hydro,gen concentrations in the a-phase) should furnish results indicative of the hydrogen positions in this phase. (12) D. M. Y a w ind .J. G, Aston. .I. Am. Chem.Poc.. 79,3619 (1952). 113) J. F:. %'orsham. M. K. Wilkinson and C. G . Schull, J . Phy8. Chem. Solid. 3 , 803 (1957).
(14) G. G. Libowitz, NAA-SR-3452. (15) G . G. Libowitz, J . Chem. Phys.. 27, No. 2 , 514 (1957).
ADSORPTION OF CONGO RED BY HYDROUS T H O R I L ? OXIDE BY RAMESHWAR PRASAD AND ARUNK. DEY Chemical Laboratories, Univeraity of Allahabad, Allahabad Received December 16, 1960
(India)
I n earlier communications1- 4 we have described the precipitation of samples of hydrous thorium oxide of different amphoterism and have studied the adsorption of inorganic ions by the different samples. The hydrous oxide precipitated with a deficient amount of alkali behaves as basic in character and thus adsorbs anions in preference to cations. On the other hand, the sample precipitated with an excess of alkali behaves as acidic in nature and has a preferential adsorptive capacit'y for cations. 'It is well known that insoluble met'allic hydroxides have an affinity to adsorb dycl molecules and are, therefore, used as mordants. Extensive studies6-s on the adsorption of dye( 1 ) R. Prasad and .4. K. Dey. Proc. .Vatl. .4cad. Sei. India, 27A. 350 (1959). (2) R. Prasad and A. K. Dey, I'ijUana P a r i . Anu. Patrika. 3 , 1.5.5 (1960). (3) R. Prasad and A. K. Dey, J . I n d . Chem. Soc., 37, 747 (1960). (4) R. Prasad and h. K. Dey, J . Sei. I n d . Res., India (communicated). (5) .4. K. Dey and S.Ghosh. Proc. N a i l . Acad. Sei. India, 1 6 8 , 143 (1946).
Xorm
July, 1961
1273
st,uffs by precipitated hydrous oxides have been carried out in these laboratories. Tewari, Dey and Ghoshg from a considerat'ion of adsorption of dyestuffs by hydrous oxides attempted to elucidate the mechanism of' aging of metal hydroxides. This paper records our observations on the association of the acid dye, congo red, with samples of hydrous thorium oxide obtained by different methods.
this case the acidic and the basic characters of the hydrous oxide more nearly neutralize each other in sample C than in others and its adsorptive power is least both for acidic and basic dyes. It will be of interest to note that Dey and Ghosh5studied the amphoteric behavior of hydrous stannic oxide and found that a t the isoelectric point, the hydrous oxide showed the minimum adsorption for both acidic and basic dyes. I n this case sample C appears to approach an isoelectric sample more Experimental Materials.--Aqueous solutions of thorium chloride nearly than others, and has the least capacity to (BDH LR), sodium hydroside (BDH AnalaR) and congo red adsorb congo red which is further confirmed by were prepared and standardized. adsorption of basic dyes also.10 The other samples, Apparatus.-The absorbance of the dye was studied with a Unicam SP 500 spectrophotometer operated on 220 volts/50 A, B and D show the adsorption in the same order cycles single phase, a x . mains with the help of a Doran depending on their diminishing basic character and stabilized mains unit. The measuring cells were glass of 10 the observations are explainable on the amphotermm. thickness, supplied n-ith the instrument. The experi- ism of the hydrous oxide. ments were conducted in an air-conditioned room maintainIt is also to be mentioned that congo red is ading 20'. sorbed considerably by all the samples of hydrous Colorimetric meaiiurements were done by using KlettSummerson's photoelectric colorimeter operated on the same thorium oxide as has been seen from the high values mains using color filter no. 50 (transmission 470 to 530 mp) of x / m in the experiments. The solutions a t chosen after ascertaining the region of maximum absorption equilibrium become very faint in color and the of the dye. pH measurements were done with an L. and N. pH indi- adsorbents assume an orange color due to the ascator operated on the same mains with a glass-calomel elec- sociation of the dye. trode system. Acknowledgment.-The authors express their Color of the Dye at Different pH.-It was found that the absorbance of the dye a t 500 mp remains constant a t pH 5.8 gratitude to the Council of Scientific and Indnstrial Research, India, for supporting the work and to 8.9 and all deterniinations were done a t p H 6.8. Validity of Beer's Law.-Beer's law was valid in the range for granting an assistantship to R.P. 4 to 12 p.p.m. of the dye and hence colorimetric estimations were done in ,this range of concentration. Preparation of Samples of the Hydrous Oxide .-Samples A, B, C and D of the hydrous oxide were obtained by adding calculat.ed amounts of a standard solution of sodium hydroside to 500 ml. of 0.251M thorium chloride solution a t 25" A precipitated with 10% deficient sodium hydroxide B precipitated with equivalent sodium hydroxide C precipitated with 5% excess sodium hydroside I> precipitated with 10yo excess sodium hydroxide The samples were thoroughly washed Rrith water till the washings were free from thorium (where present), hydroxyl and chlorine ions. The precipitates were suspended in water, vigorously shaken in a Microid Flask Shaker and the final volumes were raised by dilution with water to 10 g. of Tho2 per liter. Adsorption Experiments.-To 1 ml. of the suspension (0.01 g.), varying arnount,s of the dye were added and the volumes were raised to 100 ml. The systems were allowed t o equilibrate for 24 hours. In the supernatant liquid, the concentration of congo red was estimated by the colorimeter.
Discussion The results show that the adsorptive capacit'ies of the samples decrease mith rise in temperature. Among the four sa,mples A, B, C and D, the basic character of' the hydrous oxide diminishes in the order above mentioned, on account of the increasing amounts of a1.kali used for their precipitation. Hence, it is expected that an acid should be adsorbed most by sample A and least by sample D. The order of adsorption as noted in this paper is A > B > D > C, showing thereby that C has the least adsorpi.ivecapacity. It is well known that amphoteric bodies depend on environmental conditions to display their acidic or basic characters. It may be concluded that in (6) 9. N. Teasri, Kolloid-Z., 128, 19 (1952). (7) R. B. Hajela and S. Ghosh, Proc. Natl. Acad. Sci. Indin, 2 8 8 , 59, 118, 130 (1959). (8) S. N. Teauri and Si. Ghosh, ibid., ala, 29, 41 (1952). (9) S.N. Tewari. A. K. Dey and S. Ghosh, 2.anorp. Chsm.. 171, 150 (1953).
(IO) R. Prasad and A. K. Dey (unpublished work).
ELECTRIC MOMENTS OF SOME ADDITION COMPOUNDS OF ZINC CHLORIDE WITH ORGANIC BASES BY M. JUDITHSCHMELZ,~ M. ANNGERTRUDEHILL^ AND COLUMBA CURRAN
Department of Chetntstry, Universztv of Notre Dame, Notre D a m e , Indznna Recezved December 69. 1960
The determination of electric dipole moments of coordination compounds of zinc chloride with organic bases has been hindered by the low solubility of most of these complexes in non-polar solvents. Dioxane mas observed to have adequate solvent properties for the complexes of zinc chloride with pyridines and the picolines for dielectric constant measurements, and benzene is a suitable solvent for dichlorobis-(triethy1phosphine)-zinc. The moments of these addition compounds along with that of boron trichloride-pyridine have been determined for comparison with values previously obtained for other metal complexes. Dielectric constant measurements also were made on dioxane solutions of the complexes of zinc chloride with aniline and the toluidines but these are not reported, as spectroscopic measurements reveal that these complexes are partially dissociated in this solvent. Experimental The pyridine and picoline complexes were prepared by the addition of freshly distilled ligand to aqueous solutions of zinc chloride in mole ratios of 2: 1. The addition compounds were recrystallized from ethanol and dried over sulfuric acid. ( 1 ) Sister Mary Judith Rchmels, R.S.M.. and Sister M. Ann Gertrude Hill, O.S.U. Supported under AEC Contract AT(ll-1)-38, Radiation Laboratory of the University of Notre Dame.
