NOTES
1590
deposition on the cell window. With respect to the effect of concentration, it will be noted that an increase in the partial pressure of pentaborane from 4 t o 22 mm. had little, if any, effect on yield. This is presumably due in part to deposition of solid but may also be the result of strong or substantially complete ab~orption.~ Some further observations were made on the solid product. On rinsing with water, the material seemed to consist of small white crystals which slowly went into solution. The characteristically strong odor of boron hydrides could be detected. The freshly prepared solution was also found to reduce permanganate solution partially. The presence of borate ion was confirmed by a fluorescence test involving an alcoholic benzoic solution complex with borate ion.6 Attempts to remove the solid by hydrogenation (irradiation in the presence of hydrogen for one hour) were unsuccessful, ie., no volatile boron hydrides could be detected. The solid seemed in part to be subject to sublimation. This fact together with a rough material balance might indicate the presence of decaborane (BIoHI~). To gain some information as to the nature of the primary process, experiments with deuterium were undertaken. It was assumed that if no hydrogen deuteride was formed, the primary reaction could not have involved free hydrogen atoms. However it was found that 11 mm. each of deuterium and pentaborane irradiated for one hour produced a mixture of hydrogen, deuterium and hydrogen deuteride in approximately equilibrium concentrations (determined by mass spectrometric analysis). There is thus extensive exchange. As was to be expected, mixtures of hydrogen and deuterium on irradiation showed no exchange. It was also shown that there was no dark reaction between pentaborane and deuterium nor between deuterium and the products of the irradiation. These results suggest that perhaps the primary process is the separation of a hydrogen atom BbHg $. hv +H.+ BsHs In the presence of deuterium, exchange occurs
Vol. 60
tion number of the metal is two, and that in this state there are certain resemblances to the alkaline earth elements. We have recently shown, for example, that europium and ytterbium form dihydrides isostructural with the alkaline earth hydrides.l On the further basis of structure, density and the volatility of europium and ytterbium, in which respects a certain similarity to calcium, strontium and barium exists, it was considered that, like the alkaline earth metals, these rare earth metals may dissolve in liquid ammonia. Calcium, strontium, barium, europium and ytterbium are all either face-centered or body-centered cubic, but density considerations are more pertinent, as europium and ytterbium are distinctly less dense than their neighbors. Pading* has shown the relation of the metallic radii of europium and ytterbium to that of barium. Europium and ytterbium are much more volatile than the other rare earth metals.* The evidence suggests that in metallic europium and ytterbium, each atom contributes two electrons to the mobile lattice electrons, as in the alkaline earth metals, while in the other rare earth metals, three electrons per atom are contributed.
Department of Chemistry, Universit of Southern California, Lo8 Anodes 7, 8 a l i j . Received June 66, 1966
Experimental Solutions of Europium and Ytterbium in Liquid Ammonia. -A sim le apparatus attached to the vacuum line was used, in w h d ammonia could be distilled from sodium and condensed on the metal. The ytterbium and samarium metals were kindly supplied by Dr. F . H. Spedding, who also reduced europium salts, obtained through the couqhesy of Mrs. Herbert N. McCoy; this metal had been cast in a tantalum crucible. Both europium and ytterbium were found to dissolve in liquid ammonia at -78", forming solutions having the characteristic deep blue color of metals in ammonia. Europium appeared to be the more soluble. While no solubility measurements were made, europium solutions 1.14fand ytterbium solutions 0.25 f were prepared. Samarium was apparently insoluble. Evaporation of ammonia from europium and ytterbium solutions left golden metallic crystals, presumably the metal hexammoniates . Ytterbium in Ammonia via Electrolysis .-Efforts were made to show that ytterbium(I1) salts in ammonia could be electrolyzed, yielding solutions of ytterbium. A solution of ytterbium( 11) iodide in liquid ammonia, approximately 0.005 f, was prepared by adding the stoichiometric amount of ammonium iodide to ytterbium in ammonia. An electrolytic cell with platinum electrodes was employed. The yellFw YbIz solution was electrolyzed, and after an initial period of gas evolution, a deep blue color appeared around the cathode. The color was not stable; on diffusing outward, it disappeared with the formation of an unidentified precipitate, conceivably Yb(NH&. Europium( 11) Amide.-An attempt was made to prepare europium amide by catalytic decomposition of the ammonia solution. Europium was leached with liquid ammonia from a fragment of the tantalum crucible in which it was cast, and filtered through a sintered glass disk into a vessel holding a few milligrams of iron(II1) oxide. After standing approximately an hour, the ammonia was removed, leaving the amide and the lustrous bronze-colored metal ammoniate; the latter was decomposed, as judged by the disappearance of the golden color, by evacuation at room temperature. The gray-brown residue was analyzed for nitrogen and for europium. This gave an N/Eu ratio of 0.484, corresponding to 27.9% Eu(NH&. Presumably the pure amide could be prepared by more effective decomposition of the ammonia solution of the metal. Attempted Preparation of Europium Solutions in Ammonia by Leaching Europium Oxide Reduction Products.-
It is well known that samarium, europium and ytterbium, unlike the other rare earth elements, form a number of compounds in which the oxida-
(1) W. L. Korat and J. C . Warf, Acta Crust., 9, 452 (1956). (2) L. Pauling, J . Am. Chem. Soe., 69, 642 (1947). (3) (a) A. H. Daane, D. H. Dennison and F. H. Spedding, ibid., 75, 2272 (1953); (b) E. I. Onstott, ibid., 77, 812 (1955)
H*+Dz+HD+D
The process is completed by reaction of D or H with another molecule of BsH9 H (or D )
+ B6H9---t BrHs + HZ(or H D )
The steps leading to the conversion of the assumed B6H8. radical into diborane and into solid product are not clear. (6) C. E. White, A. Weissler and D. Busker, Anal. Chem., 19, 802
(1947).
SOLUTIONS OF EUROPIUM AND YTTERBIUM METALS I N LIQUID AMMONIA BYJAMESC. WARFAND WILLIAM L. KORST
1591
NOTES
Nov., 1956 Daane, et al.,Sa have shown that ytterbium and samarium oxides may be reduced by lanthanum a t 1450’. We thought that it may not be necessary actually to distil the ytterbium (or europium) metal away, but that mere leaching of the reaction product would serve to yield liquid ammonia solutions. Accordingly, a mixture of europium oxide and lanthanum, the former in 10% excess over the amount de2La = 2Eu La&, manded by the equation Eut03 was fired in a sealed molybdenum crucible under 300 mm. of helium pressure in an induction furnace. The temperature was maintained a t 1450-1460’ for 25 minutes. After cooling, the reaction product waa leached with liquid ammonia, but not a trace of blue color formed. The experiment was repeat,ed under much the same conditions, except that aluminum was substituted for lanthanum; the result was the same. The reduction reaction is evidently rapidly reversible, the reactants being favored at lower temperatures.
+
+
Discussion The heat of solution of europium in liquid ammonia was estimated a t -26 kcal./g. atom by the difference of two energy-cycle equations for europium and calcium. This was based on the heats of J ~first two ionization sublimation of the r n e t a l ~ , ~the potentials of the metals,6 and the difference between the heat of ammoniation of the gaseous ions, interpolating Coulter’s7 data a t the ionic radius of Eu++ (1.10 B.). Finally, the possibility that americium metal is soluble in liquid ammonia should be noted, since the position of this element in the actinide series corresponds to that of europium in the lanthanide series. Evidence supporting such a conjecture lies in the distinctly low density of americium8 compared to neighboring elements and in its somewhat low heat of vaporizati~n.~But lack of definite evidence of americium(I1) compounds and the existence of a hydride in which the H/Am ratio is approximately 2.78 would indicate insolubility of the metal in ammonia. The conclusion of Graf, et aZ.,’O that in metallic americium there are three valence electrons per atom also indicates insolubility in ammonia. This work was carried out in part under the auspices of the Office of Naval Research. (4) A tentative value of 40 kcal./g.-atom for europium was supplied by Dr. Adrian Daane. (5) National Bureau of Standards, Circular 500, “Selected Values of Chemical Thermodynamic Properties.” U. 8. Govt. Printing Office, Washington, D. C., 1952. (6) C. E. Moore, “Atomic Energy Levels,” Vol. I, Natl. Bur. Standards, Circular 467, 1949; H. N. Russell, W. Albertson and D. N. Davis, Phus. Rev.,60, 641 (1941). (7) L.V. Coulter, THISJOURNAL, 61,553 (1953). (8)E. F. Westrum, Jr., and L. Eyring, J . A m . Chem. SOC.,75, 3396 (1951). (9) S. C. Carniglia and 8. B. Cunningham, ibid., 77, 1502 (1955). (10) P.Graf, el al., ibid., 7 8 , 2340 (1956).
SOME PROPERTIES O F T H E SYSTEMS DIOXANE-BUTYL ALCOHOLS’ BY R.I. RUSH,D. C. AMES,R. W. HORST A N D J. R. MACKAY
Chemistry Laboratory, Centre CoZZege, D a n d l e , K#. Received June 87,1066
Especially because of its excellent solvent properties 1,4-dioxane has been of considerable interest t o many investigators in recent times. Binary mixtures of dioxane and water, methyl alcohol and (1) This investigation was made possible by a grant from the Carnegie Research Fund of Centre College.
.
ethyl alcohol have been studied with respect to certain physical properties such as density, index of refraction, viscosity, surface tension and vapor pressure.2-6 Several ternary systems have also been investigated.eS7 However, data relating to the physical properties of mixtures of dioxane and various other substances are not too abundant. Consequently, it seemed desirable to begin a study of some of the physical properties of binary mixtures of dioxane and organic hydroxy compounds. This paper deals with the densities, refractive indices and viscosities of the systems dioxane and each of the four butyl alcohols a t 25.00 f: 0.05’. Purification of Materials Dioxane.-1,C-Dioxane (Eastman Kodak No. 2144) was further purified by a modification of the method of Eigenberger.8 Each time before distilling as needed the product was refluxed with metallic sodium for one hour or until a fraction was obtained, on distillation, which had a refractive index of 1.4200 at 25.00’, which value agrees well with those reported in the literature cited.2-7 %-Butyl Alcohol.-Eastman Kodak No. 50 n-butyl alcohol was fractionally distilled as needed, eac,h sample used having a refractive index of 1.3974 a t 25.00 This agrees with determinations reported in the literature.9 sec-Butyl Alcohol.-Eastman Kodak No. 943 sec-butyl alcohol waa found to have a refractive index of 1.3950 a t 25.00’. Since this was in good agreement with values found in the literature,g no further purification was carried out. Isobutyl Alcohol.-It waa found necessary to purify Eastman Kodak No. 303 isobutyl alcohol. This was accomplished by a modification of a method described in Beilstein.10 That portion of the distillate having a refractive index of 1.3939-1.3940 at 25.00’was collected for use. &Butyl Alcohol.-Eastman Kodak No. 820 t-butyl alcohol, without further purification, was found to have a refractive index of 1.3849 at 25.00’, which compares favorably with values obtained by other investigators.”-14 Experimental Constant Temperature Water-bath.-Throughout the work a constant temperature water-bath was employed, the temperature being controlled by a thermoregulator. The variations in temperature were observed by the use of a Beckmann differential thermometer which was checked against a thermometer certified by the National Bureau of Standards in order to determine the reading a t 25.00’. At no time wa: the deviation from this temperature greater that f:0.05 Preparation of Solutions .-All solutions were prepared by the direct weighing of both components in a small flask having a standard taper glass stopper. The size of the flask waa such that the solutions nearly filled it. Density Determinations.-The pycnometers with the solutions contained therein were allowed to remain in a constant temperature water-bath a t 25.00 f 0.05”for a t least 30 minutes in order to reach equilibrium. Each value obtained was the result of two or more determinations.
.
.
(2) J. A. Geddes, J. A m . Chem. Soc., 6 6 , 4832 (1.933). (3) F. Hovorka, R. A. Schaerer and D. Dreisbach, ibid., 68, 2264 (1936). (4) L. W. Oholm, Finska Kemiatsamfundets Medd., 48, 19 (1939). (5) (a) R. N.Hopkins, E. S. Yerger and C. C. Lynch, J . A m . Chem. Soc., 61,2460 (1939); (b) W. A. Amis, A. R. Chopin and F. L. Padgitt, ibid., 64,1207 (1942). (6) C. H. Schneider and C. C. Lynch, ibid., 65,1003 (1943). (7) R.J. Berndt and C. C. Lynch, ibid., 66, 282 (1944). (8) E. Eigenberger, J . prakt. Chem., 130,75 (1931). (9) R. F. Brunel, J. L. Crenshaw and E. Tobin, J. A m . Chem. Soc., 43, 561 (1921). (10) Beilstein, “Handbuch der Organischen Chemie.” 4th ed. Vol. I. 1918,p. 374. (11) “Beilstein,” Vol. I, 1st Supp., Berlin, 1928, p. 192. (12) H. Adkins and W. E. Broderick, J . A m . Chem. Soc., 80, 499 (1928). (13) D. R. Simmona and E. R. Washburn, ibid., 68, 235 (1946). (14) D. R. Dreisbach and R. A. Martin, Ind. Eng. Chem., 41, 2875 (1949).
