NOTES
457
The electroneutrality conditions n ~ = ' n ~ for~ the + Helmholtz double layer and n ~ ' ncl- = nNa+for the Gouy double layer will remain unchanged when the part of n~~aggregates in the surface phase. The value of the bracketed term in eq 19 representing the KT coefficient will be given again by either eq 10 or 15. However, from the plot of y against CRfor this special case, it will be possible only to calculate n~',the total number of monomeric ions per unit area prior to surface micellization. The real equilibrium value of the area per molecule is however, equal to l / [ n ~ ~ ( l pzs zs) J since the number of molecules per unit area changes ss) due to micellization. from n R t to nR' (1 - pzs When micelles exist in the surface phase, the calculation of the real area per molecule will be difficult due to the lack of information about p and zs from the experimental data. TJnder special circumstances for the C18H37N(CH3)3+Br and C2,Hj3N(CH3)3+C1monolayers at the air-water interface, their values can be estimated from the data of cohesional p r e s ~ u r e . ~ Let us now consider the limitation of eq 10 and 15 when applied to an actual micellar system. These equations have been derived on the basis of the Helmholtz and Gouy models for the interfacial double layer. If, however, the validity of the Stern model is assumed, then $d, the potential of the diffuse part of the double layer, should replace in eq 15. For above 25 mv, it 1, and has already been shown that (1 eq 15 will be independent of the model of the double layer. We have assumed in eq 3 that the micelle has been completely dissociated, whereas experimental evidence indicates about 30 to 50% dissociation.1°-12 The degree of dissociation, however, has been shown1°-12 to be independent of the neutral salt concentration. If this is the case, then 2 in eq 15 will represent the number of the actual charge per micelle in the bulk and not the aggregation number. The charge may be assumed to be constant within the limited range of the soap concentration during the application of eq 15. Another limitation of eq 15 is that here the equilibrium concentration CR is to be plotted against y, Accuracy for the value of CR will depend upon the accuracy of determinThe third point is inn K' which is really- a pr0b1em.l~ . thstt we have neglected the activity coefficients of the
+
+
+
+
+
(10) M. L. Corrin, J . Colloid. Sci., 3, 333 (1948). (11) D. Stigter, Rec. Trav. Chim., 73, 771 (1954). (12) D. Stigter and K. J. Mysels, J . Phys. Chem., 59, 452 (1955). (13) B. A. Pethica, Proceedings of the Third International Congress of Surface Activity, Amsterdam, Vol. I , 1960, p 212.
monomer and the micelle in eq 2 and 5. Very little is, in fact, known about the activity coefficients of these substances above and even below the cmcj8and in our future analysis, an attempt will be made to take this important factor into account.
Gaseous Oxides and Oxyacids of Iodine and Xenon:
Mass Spectra'
by Martin H . Studier Chemistry Division, Argonne National Laboratory, Argonne, Illinois
and John L. Huston Chemistry Department, Loyola University, Chicago, IllinOi8 (Received August 18, 1966)
Volatility of oxygen compounds of xenon and iodine decreases in the order: Xe04, Xe03,HI04,Iz05; all are sufficiently volatile to allow their mass spectra to be observed by appropriate techniques. The mass spectra reported here were observed with a Bendix time-offlight mass spectrometer equipped with a source2modified to allow continuous, as well as pulsed, operation of the ionizing electron beam. They are presented as photographs of oscilloscope displays. The small peaks at every mass, from trace hydrocarbon impurities, werc used for precise mass determinations. Xenon tetroxide is the most volatile, most reactive, and least stable of the three known volatile tetroxides: 0 ~ 0 4 Ru04, , and Xe04. It has been made3 by reaction of concentrated sulfuric acid with the stable perxenate salts of sodium, rubidium, and barium, ie., with salts of octavalent xenon. We find that it is also generated by reaction of concentrated sulfuric acid with the explosive yellow alkali metal salts of the type K2Xe04. 2Xe03 reported by Appelman and Malm,4 providing thereby confirmation of the presence of octavalent xenon in these compounds. On the other hand, when the recently prepared6 salt of hexavalent xenon, monocesium xenate, CsHXe04, is decomposed in sulfuric (1) Based on work performed under the auspices of the U. S. Atomic Energy __ Commission. (2) M. Studier, Rev. Sci. Instr., 34, NO. 12, 1369 (1963). (3) J. L. Huston, M. H. Studier, and E. N. Sloth, Science, 143, 1161 (1964); H. Selig, H . H. Claassen, C. L. Chernick, J. G. Malm, and J. L. Huston, ibid., 143, 1322 (1964). (4) E. H. Appelman and J. G. Malm, J . Am. Chem. Soc., 86, 2141 (1964). (5) B. Jaselskis, T. M. Spittler, and J. L. Huston, ibid., 88, 2149 (1966).
Volume 71,Number Z J a n u a r y 1967
NOTES
458
acid, xcnoii aiid oxygeu arc ohserved in the evolved gases but no xetioti compounds. Mass spectrographic ohscrvatiou of xction ktroxide thus provides a simple verification of the preseucc of oetavalerit xenon in a compound. The volatility of xenou tetroxide allows its mass spectrum readily to be observed if it is gcneratcd and conducted to the source of the mass spcetromcter i n a system sufficicutly inert. Pyrex glass, fluorocarbon plastics, and fluoriuated metal have bccu used sueccssfully. The material can be purified by fractional distillatioii i n such a system. Vapor from purified samples maiutained a t Dry Ice tcmpcrnturc has heen valved to the mass spectrometer source maintairiing therciu sufficiently constant pressure to allow scans to hc made of relative inteusities of the various peaks, Xc+, 100, XeO+, 3.7, Xe02+, 8.0, Xc03+, 3.6, Xe04+, 1.4 at an ioniziug energy of 70 ev. The observed ratios were substantially constant and provided no evidence for formation in the spectrometer of lower xenou oxides such as XeO or Xe02. Mass spectra of substances of lower volatility have been observed by meaus of an apparatus origiually designed for study of surface iouizatiou.2 Samples were mounted on a platinum filament which could he electrically heated while iusertcd in the mass spcctrometer source closc to the iouiziug electron beam. Samples of xeiion trioxide have thus yiclded mass spectrii as showu in liigurc 1. The spectrum displays the typical isotopic rompositiori of xenon repeated at iutervals of 16 mass units, eorrespondiiig to Xe+, XcO+, Xe02+,and Xe03+. Again, scans of the various peaks iudicate substantial constancy of thcir relative intensities xiid 110 cvideuce for formation of lower oxides such as XeO or XeOl. The mass spectrum could be ob-
served at room temperature when the sample (which had bceu mouuted from aqueous solution) was sufficiently dehydrated to allow the ma. .pect,rometerto be operatcd, and hceame more intense when the sample was heated. No oxyacid of xerioii such as H,Xe04 could be ohserved, indicating that whatever may he the extent of hydration of "xenic acid'' iu aqucous solution, no sufficiently strong assoeiatiou to the solvent exists t o produce an oxyacid in the gas phase. Observation of the existelice of XeOI in the vapor phase eucouragcd us to try purification of the material by molecular distillatiou. The distillatiori proceeds with some decompositiou to xciioii and oxygen, yields of recovered XcOa rauging from 50 to 75% as shown by titration. The distillatiori takes place convenieutly around 70" with the distillctl mat.crial depositing as a white solid on the walls of the glass apparatus. In oue experiment, it was distilled outo a surface ionization apparatus which was t,hen inserted into the mass speetrometer to verify that the deposited material was in fact XeOs. AIost distillatious have been done suci:essfully whcn quantities of around 20 mg of matmial were used, but some have resulted in cxplosious which broke the contaiuiug glass apparatus. Two attempts were made to distil 100 mg, but in both cases explosions resulted. Periodic acid samples were placcd iii the mass spectrometer i u the same maimer as xciiori t,rioxide and the mass spectrum observed a s showu in I+gnre 2. S o m e what higher filamcut tcmpcraturc mas required than for XeOa. The mass of parent HIO, was identified by reference to the mercury spectrum, couiitiug down from
I+, HI'
,'OI HIO'
Figure 2. Rlass spectrum of periodic acid
The J o u d ofPhysica2 Chemialrg
+\ +
IO;, HIO; HI04 Hg HI03
NOTES
459
lower oxides as LO. However, IO+ and IO2+ were also observed along with the dimeric iodirie species of Figure 4 arid were seen t o uudergo marked fluctuations in intensity relative to the dimeric species, thus indicatiug ari independent existence for IO? in the gases produced by vaporization of IzOs.
Acknowledgment. We are grateful to Mr. Leori P. Moore for technical assistance.
&
Concerning the Spectroscopic Determination
1’ HIi
IOt, HIO’
IO;
HI05
Hg’
Figure 3. Mass spertrum of iodic acid.
of the Structure of Water
by Gerhard Boettger, Hartwig Harders, Rechenzentrum der Badischrn Anilin- & Soda-Fabrik AG, Ludwioshafen am Rhcim
and Werner A. P. Luck Harrptlaboratoririm der Badisden Anilin- & Soda-Fabi-ik AG, Ludwigshafon am Rhein. Gcrmny (Rrceiue,l Februar~25. l g l X )
Figure 4. Mass spectrum of iodine pentoxide
19s to 192. Hypoiodous acid was formed as an independent species. It varied in intensity relative t o the other peaks and persisted in the mass spectrometer after heating of the sample had been discontinued and the spectrum of HIOnitself could no longer be observed. Ro evidence was obtained for periodic acid anhydride, Ip07. Iodic acid similarly mounted on a filament yielded the mass spectrum of H I 0 3 as shown in Figure 3. After the sample was sufficiently dehydrated, heating of the filament caused sufficient volatilization of IIOs to give the mass spectrum of Figure 4. Scans of these various peaks showed no substantial variation in relative intensities and no evidence for formation of such
I n a former publication, it was attempted to estimate the approximate proportions (if open and closed hydrogen bonds of water (from the change of iiifrared bands) in order to test the available theories concerning the structure of watcr.’ By exteusive measurements up t o and above the critical it mas attempted to increase the probability of the approximations. During these measurements, Buijs and Choppin’ reported a method of calculat,iori in which, by use of measurements in a small area of temperatures, the relative concentrations of the iudividual species of water without H bonds, co, with one H bond, cI, and with two H bonds, el, and also the unknown extinction coefficients could he determined. Therefore, they took the gross molar extinction coefficients E”’ at three wavelengths X. (n = 1, 2, 3) and at different temperatures T,(i = 1 , 2 . . . .).
(1) W. A. P. Luck, Vortrng Tagungder Deutsehen Bunsengesellsehnft fllr l’hysikdische Chemie. RIUnster, Feb G. 1962: Z. Eleklmhem., 66,766 (1962): Be?. Rtmscnges.. 67, 186 (1963). (2) W. A. P. Luck, Fortschr. Chom. Forsch., 4, 653, 877 (1964).
(3) W. A. 1’. Luck, Nachr. Chem. Teehnik. 12, 345 (1904). (4) W. A.
(5)
1’.
Luck, Ber. Bunswes., 68, 895 (1964): 69, 69 (1965).
W.A. P. Luck, ibid., 69,626 (1965).
(6) W. A. 1’. Luck, NoArrwlissmchajtrn, 5 2 , 25, 49 (1965). K.Bugs and G . R.Choppin, J . Chrm. Phgs., 39, 2035 (1903).
(7)
Volume 71, Nvmbcr B Janzrary 1967
