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COMMUNICATIONS T o THEEDITOR
absorption reaction. Although no COz evolution was detected, appreciable amounts of acetic acid were found in the reaction mixture.6 Table V presents relative reaction rates for the hydrogen-evolution reaction in a nitrogen atmosphere. The eight metals investigated are those which showed appreciable reactivity in ai1 oxygen atmosphere. It may be noted that lead, which had the highest reactivity with acetylacetone in oxygen, did not undergo the hydrogen evolution reaction
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at a measurable rate. Only Mg, Mn and Zn reacted at ail appreciable rate (a fourth, indium, exhibited a small but measurable reactivity) ; and these are the three which were found to yield hydrogen during oxygen absorption, in the same order of reactivity. Acknowledgment.-The writers are grateful to Dr. W. M. Hickam and his group for mass spectrometer analyses, and t o Dr. J. H. Lady for infrared spectra.
COMMUNICATIONS TO THE EDITOR T H E MECHANISM OF THE HYDROGEN magnesium ~ h l o r i d e . ~ . ~The J data on magnesium EVOLUTION REACTION ON PLATINUM, chloride given in the three references do not agree SILVER, AND TUNGSTEN SURFACES IN very well with each other. We have determined the surface tension of ACID SOLUTIONS : CORRECTION several alkaline earth metal halides a t temperatures ranging from near the melting points up to about Sir: We wish t o point out that in our recent publi- 1000°. Table I gives the coefficients of linear cation, it was implied that electrodes used in experiTABLEI ments reported by Schuldiner2w a e to be classed as TENSION DATAFOR SOMEALKALINE EARTH having been in a “nonactivated state.” In fact, THESURFACE HALIDES Schuldiner’s results were plotted as a function of a “real” current density calculated from double y = a - bt where y = surface tension in dynes/cm., t = temperature in “C. layer capacity measurements. Recalculation of Standard TemSchuldiner’s results on an “apparent” current deviation perature density scale brings them into a range characteristic in dynes/ range om. in O C . a b Salt of “activated” electrodes. Schuldiner’s later re1.3 865-1009 205.2 0.0617 sults differ by only a few mv. a t a given current BaBrz 1.0 884-1034 0.0553 SrClz 217.3 density from those of the present workers, the 1.5 657-1011 178.0 0.0439 SrBr2 comparison being made in aqueous solutions con1.0 577-987 0.0383 SrIz 134.8 taining, respectively, Hi304 and HC1, a t approxi0.3 774-809 0.0459 CaBr2 153.1 mately the same strengths. Better agreement 1.5 795-1052 98.7 0.0174 Ca12 could not, in the present author’s views, be expected. equations for surface tension as a function of JOHNHARRISON LABORATORY OF CHEMISTRY temperature. These coefficients were derived by UNIVERSITY OF PENNSYLVANIA J. O’M. BOCBRIS the method of least squares frpm data obtained by PHILADELPHIA, PA. the maximum-bubble-pressure technique. None of (1) J. O’M. Bockris, I. A. Ainmar and A. K. M. 8. H u q , J . Phys. the fluorides have been measured yet because of Chem., 61, 879 (1957). their high melting points. The magnesium hal(2) 8. Schuldiner, J. EEecLrochem. floc., 99, 488 (1952); 101, 420 (1954). ides are being investigated but satisfactory data have not yet been obtained. RICHARD B. ELLIS SURFACE TENSION OF FUSED BLKALINE SOUTHERN RESEARCH INSTITUTE JOSIAH E. SMITH EARTH METAL HALIDES EVELYN B. BAKER BIRMINGHAM 5, ALABAMA RECEIVED MAY9, 1958 Sir: In view of the current interest in high tempera(1) “International Critical Tables,” Vol. IV, McGraw-Hill, New ture chemistry, a fundamental research program t o York, N. Y., 192G,p. 442. study the surface tension of fused salts has been (2) J. S. Peak and M. R. Bothwell, J . A m . Chem. Soc., 7 6 , 2G5G undertaken. The reported surface tension data (1954). (3) V. K. Sementshenko and L. P. Shihobalova, J . Phus. Chem. on fused alkali metal halides is reasonably complete; , 21, 707 (1947). however, this is not the case for other periodic U S(4)S RV. P. Barzakouski, J. AppZ. Cham. U S S R , 18, 1117 (1940). groups. The alkaline earth metal halides are of (6) V. P. Barzakouski, Bull. Acad. Sci. U S S R , Classe Sci. Chim., considerable interest in fused salt technology, but No. 5, 825 (1940). ( G ) V. Zhivov, Trans. B A M I , No. 11-12 (1935). surface tension data are available for only three: L. Strelets and 0. G . Desyatnikov, J . A p p l . Chem. U S S R , barium ~ h l o r i d e , ~ ,calcium ~J,~ ~ h l o r i d e ~ , ~ and , ~ - ’ 28,(7)35 Kh. (1955). (1) This work was sponsored by the U. 8. Atomic Energy Coinniission under Contract AT-(40-1)-2073.
( 8 ) L. Ya. Kreiunev, A. I. Feklinov and K. P. Mischenko, Tmenlnye M e l d , 19, No. 6 , 51 (1946).
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