NOTES
2086
sample. The sealed tube runs on the 10 and 70% gallium oxide mixtures gave results identical with those obtained in open foil envelopes. No compounds of gallium oxide and Si02were encountered in this study. The 50, 60 and 70% Ga203compositions were heated a t solidus temperatures, and also a t 1550 and 1450" for 24 and 48 hours, respectively. Only @-Ga203and cristobalite were present in the runs. Thus no gallium analogs of mullite (3A1203.2Si02)or the A12SiOspolymorphs are stable a t high temperatures. The high temperature liquid immiscibility in the Ga203-Si02 system is another feature not found in A1203-Si02.4
1800~
Vol. 63
The observed electromative forces and values of the activity coefficients are recorded in Table I . TABLE I THE ACTIVITYCOEFFICIENT O F HYDROCHLORIC ACID CADMIUM CHLORIDE SOLUTIONS T = 25"; pT = p1 pp = ml 3mg = 5
+
IN
+
ml
E
log. Yl
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5
0.09519 ,10906 ,12359 ,13859 ,15390 ,16935 .18529 .20253 ,22245 .25009
0,3766 ,2896 ,2001 .I102 ,0224 - ,0600 ,1574 - ,2114 ,2822 - .3550
-
This contribut,ion was supported in part by The Atomic Energy Commission under Contract AT (30-1) 1375
I
1500-
c n JIW2
2o
40
60
Mde % Ga,O,.
-
80
r
,-.
b o Z "3
Fig. 1.-Phase relations in the system Ga2O3-Si02. Solid dots represent the temperature of critical quench runs.
Phase relations in the Fe203-Si02 systems are not known a t liquidus temperatures because of the difficulty of maintaining the iron in the ferric state, so that no direct comparisons can be made with other M203-SiO2 systems. An extrapolation of data obtained at oxygen pressures of 1 atmosphere and less6 indicates that extensive liquid immiscibility exists in the Fe2O3-SiOa system. It may be suggested, therefore, that melting relations are similar in the systems Ga2O3--SiOzand Fez03Si02. (4) N. L. Bowen and J. W. Greig, ibid., 7 [41,242 (1924); with corrections by J. F. Schairer, ibid., 26, 243 (1942); further revision suggested b y N. A. Toropov and F. Ya. Galakhov, Doklady Akad. Nauk S.S.S.R., 78 [2],301 (1951). ( 5 ) A. Muan, J . Metals, 7 [9],965 (1955).
THE ACTIVITY COEFFICIENT OF HYDROCHLORIC ACID IN CADMIUM CHLORIDE SOLUTIONS AT 5 M TOTAL IONIC STRENGTH BY HERBERTS. HARNED AND ROBERT GARY Contribution N o . 1669from the Department of Chemistry of Yale University, NEWHaven, Conn. Received June 66,1959
As a further contribution to the st.udy of the systems containing two electrolytes in water, the activity coefficient of hydrochloric acid in cadmium chloride solutions a t 5 M total stoichiometric ionic strength has been determined at 25' from measurements of the cells H 2 lHCl
(mi), CdClz
(mz)lAgC1-Ag
ELECTRON PARAMAGNETIC RESONANCE STUDIES ON CARBON DISULFIDEINSOLUBLE SULFUR BY A. G. PINKUS A N D L. H. PIETTE~ Department 01Chemistry, Baylor University, Waeo, Texas, and Varian Associates, Palo Alto, California Recez'ved J u l y l.$?1969
Recently,2 a close-packed helical structure was uggested for crystalline polymeric carbon disulfide -insoluble sulfur obtained from the slow cooling of a purified sulfur melt in order to explain the similarity of its X-ray diffraction pattern to that of orthorhombic sulfur.3 A more extended helical structure also had been suggested recently for the fibrous constituent of stretched plastic s u l f ~ r , ~ , ~ Dads white sulfur,6.6 and for "supersublimaIt was pointed out2 that stereotion" chemical considerations exclude a macrocyclicS structure for the close-packed helical configuration and suggested that electron paramagnetic resonance determinations on the insoluble sulfur would distinguish between the biradical (I) or three-electrori bond (II)9 structures on the one hand and the ionic structure (111) on the other. In their classical paper,'O Gardner and Fraenkel previously had re(1) Varian Associates.
(2) A. G. Pinkus, J. S. Kim, J. L. McAtee, Jr., and C. B. Concilio, to be published. (3) A. G. Pinkus. J . S. Kiln, J. L. McAtee, Jr., and C. B. Concilio, J . A m . Chem. Soc., 79, 4566 (1957). (4) L. Pauling, Proc. Nat. Acad. Sei., U . S.,35, 405 (1949); J. A. Prins, J. Schenk and P. A. M. Hospel, Physica, 22, 770 (1950);A. R i m monti and C. Vacca, Ricerca Sei., 28, 1880 (1958). ( 5 ) S. R. Das, Indian J . Phys., l a , 163 (1938). (6) J. A. Prins, J. Sohenk and L. H. J. Wachters, Physica, as, 746
(1957). (7) Product of Stauffer Chemical Co. having the registered trade name of "Crystex." ( 8 ) H. Krebs and E. F. Weber, Z. anorg. allgem. Chem., 272, 288 (1953). (9) F. Fairbrother, G. Gee and G. T. Merrall, J . Potymer Sei., 18, 459 (1955); G.Gee, Science P r o g ~ e s sNo. , 170, 193 (1955). (10) D. M. Gardner and G. K. Fraenkel, J . A m . Chem. Soc., 18, 3279 (1950).
6
NOTES
Dec., 1959 ported conclusive paramagnetic resonance evidence for the existence of long-chain biradical poly.S+S)-S.
.. .. ..
:&2+(s),-2-s~:..
.. .. *.
..
.. ..
&-(S)-S@
*.
I I1 I11 mers in liquid sulfur. I n the present paper, we report our findings. Results and Discussion A determination on a carbon disulfide-insoluble sample of “supersublimation” sulfur showed a resonance signal a t g = 2.0044,which is close to the g value of 2.0023 for a free electron.ll This result constitutes definite evidence in favor of structure I. It should be noted that the line (Fig. 1) is asym-
kg2;?-1 n
W
Fig. 1.-Electron paramagnetic resonance absorption line for carbon disulfide-insoluble supersublimation sulfur.
metric and thus unlikemost organic free radical lines. This asymmetry is indicative of anisotropy in gl and gll which is a result of an appreciable amount of spin-orbit coupling, the unpaired electron being localized on the sulfur in a p orbit. In comparison, the average g value found by Gardner and Fraenkell0 for liquid sulfur was 2.024,a value which is shifted ever further from the g value for a free electron. The general interpretation has been madelo that shifts in g-values for molecules in nondegenerate orbital ground states increase with the magnitude of the spin-orbit coupling and decrease with the separation between ground and excited states. The absolute concentration of unpaired electrons was estimated to be about 1 X mole/l. which can be compared with the value 1.1 X 10+ found by Gardner and Fraenkel’O for liquid sulfur a t 300”. The number average chain length ( p ) of the sulfur helix polymers was calculated to be 1 X lo7 using the relation:1° p = (1000/32)(p/Cc), where p the density was taken as 1.95 g./m1.12; the concentration of helix fragments (C,) taken as 5 X 10-6 mole/ l.,la assuming two independent electrons per helix fragment. The corresponding values obtained by Gardner and Fraenkel‘O for liquid sulfur were (5.0 2.5) X lo4 a t 300” and a maximum value of (1.5 f 0.7) X lo6 at 171”. Thus, the value obtained in the present work appears to be in the right order of magnitude. Based on the information that the sulfur particles are spheres with an average diameter of 2 to 4 p,la an estimate of the average number of helix chains per sulfur particle (aa) can be calculated = NDPC,/2, where N = from the relation: Avogadro’s number, D = density, V = volume of
*
(11) J. E. Werta, Chem. Reus., 66, 829 (1954). (12) The Stauffer Product Report No. 819 A lists this value for Crystex. (13) Stauffer Product Report No. 819 A.
2087
the sulfur sphere, and Cg = absolute concentration of electrons in mole/g. The calculated value is (2 to 4) X 104 helix chains per sulfur particle, assuming two odd electrons per helix chain. Since X-ray diffraction patterns reveal a regular crystalline structure for this form of sulfur,6s6it is reasonable to postulate that the helix chains are oriented with their central axes parallel. This arrangement would of necessity locate the odd electron ends of the helix chains a t opposite ends of the spherical particle and would result in the localization of the unpaired electrons which would explain the anisotropy suggested by the asymmetry in the absorption line noted above. Experimental The measurements were made on a Varian Associates Model V-4500 E-P-R Spectrometer. The g-value of the sample was calibrated by placing a small amount of 1,l-diphenyl-2-picrylhydrazyl in the sulfur sample. This mixture showed a slight shift from the known” g-value of 2.0036 for l,l-diphenyl-2-picrylhydrazyl. The concentration of unpaired electrons was estimated by comparing the first moment of the line from a 500-mg. sample of sulfur with that from a 5 X 10-* M solution of vanadyl sulfate (containing the VO++ ion), using one line of the 8-line spectrum of the latter. The concentration of unpaired electrons determined in this manner was 5 X 10-9 m?le/g. A sample of “supersublimation” sulfur14 weighing 9 -82 g. was extracted with 200 ml. of redistilled ACS grade carbon disulfide by means of a Soxhlet extractor. After three extractions (totaling 47 hours), the amount of insoluble material remaining after drving to constant weight in VUCUO at room temperature was 8b.3%.ls
Acknowledgment.--Helpful discussions with Professor Charles E. Reeder of Baylor University are gratefully acknowledged. (14) Specifications and properties of this form of sulfur (“Crystex”) are described in several Stauffer technical data sheets, product reports and a brochure entitled, “Stauffer Sulfure.” The authors thank the Stauffer Co, for a n experimental sample. (15) This does not necessarily represent extraction to constant weight since there was still a small percentage of material extracted during the third extraction. However, since according to the Stauffer Technical Data Sheet No. 717 Y,“Crystex” undergoes slow reversion t o soluble sulfur (the rate increasing with increase in temperature), i t is possible that this is the reason for the inability to attain a constant weight b y repeated extraction.
COMPLEX FORMATION CONSTANTS OF LEAD AND CADMIUM IONS WITH CHLORIDE I N FUSED LITHIUM PERCHLORATE’ BY FREDERICK R. DUKEAND WALTERW. LAWRENCE Institute for Atomic Research and Department of Chemistry, Iowa State University, Ames, I o w a Received July 99,1969
Complex formation constants involving lead and cadmium ions with chloride ion have been determined in a fused KN03-NaN03 eutectic.2 It is of interest to compare the complex formation constants in a nitrate solvent with those in a perchlorate. Lithium perchlorate is the only stable fused perchlorate and it has been shown to dissolve insignificant amounts of water a t low h ~ m i d i t y . ~ Therefore the constants were determined in fused (1) Contribution No. 780. Work was performed in the Ames Laboratory of the U. S. Atomic Energy Commission. (2) F. R. Duke and M. L. Iverson, THIBJOURNAL, 62,417 (1958). (3) F. R. Duke and A. Doan, Iowa $tale Colleoe J . Sci., 89, 451 (1958)-
