COMMUNICATIONS TO THE EDITOR
1566
ence as that of Hunt and Taube, his method would give a value of 1.0425 a t 15'. A value of 1.045 f 0.003 a t 15' seems to be compatible with both experimental and theoretical data. A similar sort of argument points to a value of 1.040 f 9.003 a t 25'.
Vol. 67
Acknowledgment.-This work was supported by the National Science Foundation under Grants G-5411 and G-17422. hl. G. wishes to express his gratitude to the United States Educational Commission in the United Kingdom for a travel grant.
COMMUNICATIONS TO THE EDITOR CATIONIC ;CIBBILITIES IK FUSED CESIUM KITRATE AND THALLOUS SITRATE
Sir : In the course of tlie past few years many papers dealing with the determination of transport numbers of ions in pure ionic melts have been published. Most of the experiments were made with porous plug cells1-4 in which the plugs act as reference frames for the ionic velocities. I n our present work we used the experimental technique of electrophoresis on thin layers for the determination of single ionic mobilities in molten salts. The layer consisted of fine alumina powder sprayed on a sintered non-porous alumina support strip (30 cm. X 1.5 cm. X 2 mm. thick). The thickness of the layer was about 10 mg./cm.2. It was impregnated with the pure salt under test and doped at one end with a small amount of radioactive cations. The cell terminals consisted of two platinum electrodes immersed in the melt contained in crucibles. The electric connection between the crucibles and the strip was achieved by asbestos paper bridges. The potential gradient along the alumina strip during the experiments was measured by two auxiliary platinum wire electrodes in contact with the strip at both ends. The mobility data reported are referred to this potential gradient. Under normal experimental conditions the field strength was 3-6 v./cm. and the running time was 1-2 hr. The current was 10-45 ma., which corresponds to a maximum Joule heat of 0.2 w./cm.2. This value is small enough to avoid temperature differences along the strip. When the experiment was completed, the strip was cooled to room temperature and the activity distribution scanned by a G.M. window counter in which the aperture was 0.5 mm. I n Table I we compare a few results obtained for alkali nitrate melts with those obtained by other authors who determined the porous plug transport numbers in the same systems. We also give original results for cesium nitrate a t 450' and thallous nitrate a t 250'. The mobilities in the third column are the results of runs carried out a t different potential gradients. (1) B. B. Owens and F. R. Duke, Ames Laboratory, Iowa State College, Unclassified Report USAEC ISC-992. ( 2 ) R. W. Laity and F. R. Duke, J . Electrochem. Sac., 205, 197 (1958); "Metals Reference Book," Butterworths Scientific Publications, London,
1955, pp. 614-627. (3) A. Klemm, Discussiuns Faradag Sac., 83, 203 (1961). (4) E. D. Wolf and F. R. Duke, Ames Laboratory, Iowa State University, Unclassified Report USAEC 19-334.
TABLE I CATIONIC MOBILITIES OF PUREFCSED SALTS u x 104, T, Salt
CSNO~
Tlxoa
oc.
450
250
cm.2 v.-1 sec.-1
1.56 1.69 1.64 1.08 0.99 1,04
Av.
Previous work
1 . 6 3 zt 0.07
...
1.05iO.06
...
1.11
NaNOB
350
3.86 3.90 3.84
3.87 zt 0.07
3.86 i 0.05a
KNOa
350
2.04 2.08 2.12
2.08 f 0.06
2.21 f 0.11"
AgN03
250
Reference I .
2.57 2.68 2.57 f 0.11 2.47 Reference 2.
2.87 f 0.1gb
We feel that electrophoresis on thin layers in fused salts is an accurate and useful method for determining electrical transport properties of ionic melts. DIPARTIMENTO MATERIALI CHIMICA ALTE TEMPERATURE C. C. R. EURATOM ISPRA-VABESE, ITALY RECEIVED JANUARY 29, 1963
S. FORCHERI C. MONFRINI
PHOTOCHEXICAL REACTION OF HYDROGES BROMIDE WITH OLEFINS AT LOW TEMPERATURE
Sir: A recent electron spin resonance study of the interaction between ultraviolet irradiated hydrogen bromide and various olefins1 has been interpreted in terms of radicals formed by addition of a bromine atom to the double bond in such a manner that bonding is effectively symmetrica1.l The alternative reaction considered was hydrogen atom addition, but this was excluded on the grounds that the spectra were not those expected for alkyl radicals, and, for reaction with cyclopentene and 2-butene, spectra were identical when deuterium bromide was used instead of hydrogen bromide. (1) P. I. Abell and L. H. Piette, J . A m . Chem. Sac., 84,916 (1962).
