S T
Rosner and Allendorfi have recently reported expcrimclntai dala err the fluorination rate of solid tungsten \vhich revealed B sharp drop in reactivity above B filament I~x~iperaiure of 2080°K. Based on a compazison cf thew data with the quasi-cquilibrium ) model oi BalC? and 8tickney,213they concluded ('the q~i~,6i-ccj-Luiibrrurn model, rombined with presmtly available ~ ~ e ~ m o c h e m i cdata, al does not provide a selC-consistcnL explanation of our observed vior for the W(B)-F(g) reacticn " Kowever, one reaEon for reaching this conclusion was that, based on 1,hc tluaci-c.quil;briurn model and avallablc Rosner t ~ ~ e r ~ ~ o data c h efor~ ~ Fc(g) ~ ~ ~and ~ , F(g), ~ and Ailcndoi-E iotiritl tha6 the predicted transition in dominant ;TRC ion Ijrdurt from WFs(g) t o F(gj occurred beloto :.?OOfJ"BL We wish to point out here that while their R P itljrsis apptws to bc correct, the temted occurs perature ad 11 hich the ~ ~ - p ~ e d i c transition lue (-2800°K) corresporiding Hence, we suggest that the wlren c o ~ ~ b ~ nwith e d availtent with Rosner a,nd Allendorf't4 data To pro-vidtl 6-p ~ m r edetailed comparison of the QE predictions 111 / 13 ihi. experiment a1 data of Rosner and Allentlorf, we have performed a complete analysis similar to -t bai le bed in ref 3 for the 02-Wreaction. The rrsults $IF shown in Figure I, which. is a reproduction of li'igurc. 4 of Kosner and Allendorf] except for Sir:
I
our addition of the curves representing the quasiequilibrium predictions. For simplicity, wc have approximated their data for T 1/8; see especially the Mo/F data of re%a), when combined with the QE underpredictiorn of sates (in the only portions of Figure 1 of ref I which are honufide predictions) seem to us to preclude WPs(g) as the only significant W-containing product, especialLy above 2000°K. Moreover, it is significant thac the $E underpredictions of rate above 2000°K (well over three decades at 2500°K) far exceed discrepancies that could reasonably be attributed to experimental tmcertainties in (i) reactant arrival rate, F6(g) thermochemical data, and/or (iii) oxygen impurity level. Without more complete thermodynamic data for the gaseous tungsten fluorides and/or product distribution measurements for this and similar reactions it IS difffcult (i) to decide on the accuracy of QE in the W-F2 reaction and (ji) to answer the more subtle question of whether the assumptions underlying QIC models3%* break down for atom-metal reactions in which product formation by Rideal-Eley elementary steps may play an j mportant role.5 indeed, the use of atomic reactants to study the gasification kinetics of refractory solids6i7 could shed light on this interesting question.2
Optical Absorption of Solvated Electrons in Alcohols and Their Mixtures w i t h ~
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Publication costs aasisted by the U. S. Atomic Energy Commission‘
Sir: As noted by other^,^-^ the dc:ohok and their lar~y mixtures, especially with alkanes, are ~ a ~ t ~ c : ~suitable media for study of the factors that in formation, structure, and decay of solvated electrons. We have initiated a broad and thorough atllzdy of the time dependence of solvated electron a,bsorption spectra in such media. The initial results of that study are of special interest and significance in rrlat1oi.i t o certain previously published experimental viork294-6 and m o d e l ~ l * - ~for ~ the solvated electron. Absorption spectra have been determined for the solvated rlectron in 22 alcohols (for 15 of which i,he eS- spectrum has not been reported) and in binary mixtures of a number of alcohols and cyclohexane. Soriie qalierrt aspects of the results are reported in this ~ o n ~ ~ ~ ~ ~ ~ c a ~ The best avnilable grade of each alcohol TVBS purified by distillation wit,R a Nester-Faubt spinning-band column. Water content of an sllcohol ~ B V F I ’exceeded 0.2% and generally was less than Certified cyclohexane was used witlaou fication. Solutions were deaerated by aiitrogeri bubbling and irradiated in 1-em quartz c d a a t --.30” with 5or 10-nsec pulses of - J S - M ~ V eiiectroras (estiraated dose per pulse of -1019 eV from bhe Notre Arco Model LP-7 linear accelerator, The light for rnensurement of +,heoptical absorption1 wn,s a 450-W xenon lamp (Ushio UXL 451-0) that was p d s e times the steady-state output Cor a 5-anwc period within 11hich the absorption WRS recorded. Trans-
(1) The Radiation Laboratory of the Univcrsaty of Notre Dame is operated under contract with the U. S Atomic Energy Commission. This i s AEC Document No. COO-38-851. (2) M. C. Sauer, Jr., S. Arai, and 1,.M. Dortman, J . Chem. Phys., 42,708 (1965); 1,. M . Dorfman, Adaan. Chem. Ser., Mo,SO, 36 (1965). (3) S. Arai and M C Sauer, Jr., J . C h ~ mk“h$,s., . 44, 2297 (1966). (4) T . J. Kemp, G, A. Salmon, and P.Wardman in “Pulse Radiolysis,” M. Ebert, J. P. Keene, A. J. Swallow, and J . W Baxendale, Ed., (1) P. C. Abbott and R. E. Stickney, J. Phys. Chem., 75,2930 (1971). hcadeniie Press, London, 1965, pp 247-287. (2) D. E. Rosner and H. D. hllendorf, ibid., 75, 308 (1971). (5) B. J. Brown, N. T Barker, and D, F. Bangster, J . Plays, Chem., 75,3639 (1971) (3) J. C. Batty and R . E. Stickney, J . Chem. Phus., 51,4475 (1969); see also J. E. Franklin and R . E. Stickney, High Temp. Sci., 3, 401 (6) L. B. Magnusson, J. T. Richards, and J, K Thomas, I n t . J . (197 1) Radiat. Fhgs. Chem., 3,295 (1971). (4) J. C. Batty and R. E. Stickney, Ozid. Metals, 3,331 (1971). (7) J. X-P. Baxendale and P. Wardman, N a t w e (London), 230, 449 (1971). (5) D. E. Rosner and €3. D. Allendorf, J. Electrochem. Soc., 114, ,306(1967). (8) J. T. Eichards and J. I
