NOTES
654
reagent grade methylene iodide was distilled under reduced pressure before use. Fisher “Purified” reagent grade 1,Cdioxane was further purified by Fieser’s method (procedure a).l4 (+)-1,l’-Binaphthyl was prepared by the method of Harris and lIellor,lz Details, including minor modifications of their procedure, will be published elsewhere. The optically active binaphthyl mas obtained as white crystals varying in physical properties from m.p. 156-159’ (uncor.), [ a ] +154’ ~ (benzene) to m.p. 157-160’ (uncor.), [ a ] +192O: ~ reportedlj m.p. 157-159’, [a],,,, + 2 4 5 O . Kmetzc PI*OC&IV.A solution of (+)-1,1‘-binaph31) was transferred to a thy1 (generally ea. 3 x 2-dm. jacketed polarimeter tube maintained at constant temperature by circulation of water from a constant temperature bath. After allowing 10 min. for thermal equilibration, 80 to 100 readings were taken, starting alternately from higher and lower angles of rotation. The reaction was found to follow strict first-order kinetics through three half-lives although in some cases the reaction was followed to only 60-70% completion. Initial readings were in the range 2.1 to 1.7”, depending on the rate of the reaction and the initial purity of the binaphthyl. The data were analyzed graphically by plotting log (at - a,) us. time. Errors in the choice of the best fit straight line are estimated to be less than +1yG in slope or rate constant, except as indicated (Table 1).
Acknowledgment. We wish to thank the Kational Science Foundation for a grant in support of this research. (14) L F. Fieser, “Experiments in Organic ChemistrJ ,” Third E d , D. C Heath and Company, Boston, 1955, p 225 (15) ;I?M Harris and A S Mellor, Chem Ind (London), 1082 (1961)
of the literature revealed only an estimate of 2.0 for the molar refractivity,2 corresponding to an index of refraction of 1.10. Since an experimental value for the refractive index of anhydrous liquid HF is of interest, this note reports its determination.
Experimental A s the anhydrous H F had t o be kept in a closed unreactive system. the refractive index measurements were made using a hollow prism and spectrometer similar to that used by Stein, T’ogel, and L ~ d e w i g . ~ The prism was made of nickel with replaceable sapphire 15indows sealed with Teflon gaskets. 111 addition to the sample space, passages for the circulation of constant’ temperature water were drilled in the prism providing temperature regulation to within * 0.05’. Following Tilton’s4analysis of the Frauenhofer method of minimum deviation for the determination of indices of refraction, the hollow prism had a refracting angle of 80’. For an error of +0.0001 in refractive index, this angle allows a tolerance of 1.0 min. of arc for n = 1.3 and 3.0 min. of arc for n = 1.1 in the measurement of refracting angle and tolerances of 1.25 to 1.7 min. of arc for n = 1.1 to 1.3, respectively, in the measurement of twice the angle of minimum deviation. The spectrometer employed was a Spencer hlodel 10025 with a vernier reading to 1 min. of arc. I n order to minimize errors, since the circle was uncalibrated, angle measurements were carried out as prescribed by Tilt~n.A ~ General Electric sodium Lab-Arc was used as the source of the sodium D-line, and Beckman hydrogen and mercury lamps with appropriate interference filters were used 3 s sources for wave lengths of 6562, 4861, and 4358 A. in the measurements of dispersion. The anhydrous HF was prepared by fractional distillation in the still described by Katz and Sheft.6 Two diff erent samples were used, each having a specific conductivity of 2 X mho.
Discussion of Results The Refractive Index of Anhydrous Hydrogen Fluoride1&
by 9..J. PerkinsIb Argonne S a t i o n a l Laboratory Argonne, IlEinoia (Receiwd Octobcr 7 , 1968)
The value of the refractive index of anhydrous hydrogen fluoride was needed in connection with studies of the Ranian spectra of HF-BrFb solutions. A search The Joz~rnalof Physical Chemistry
The refractive indices of anhydrous H F a t 2.5’ for four different wave lengths are given in Table I. The indices of the two different samples agreed with each other to f.0.0001. The molar refractivity calculated ~~~~~~~
(1) (a) Based on work performed under the auspices of the U. S. Atomic Energy Commission. (b) University of Illinois, College of Pharmacy, Chicago, II1. (2) C. P. Smyth, “Dielectric Constants and Molecular Structure,” Chemical Catalog Co.. New York 19, N. Y. (3) L. Stein, R. C. T-ogel, and W. H. Ludewig, J . Am. Chem. Soc., 76,4287 (1954). (4) L. R. Tilton, J . Res. Sat2. B u r . Std., 2 , 923 (1929). ( 5 ) J. J. Katz and I. Sheft, Chem. Eng., 223 (1961).
NOTES
655
Table I : Refractive Iindex of Anhydrous HF a t 25" x
n
4358.3 4861.3 5892,6 6862.8
1,1598 1,1586 1.1574 1.1567
on the basis of a molecular weight of 20.01 using the sodium D-line index is 2.13 cc. The refractive index as a function of the wave length can be represented within *0.0001 unit through the visible region by the simple Cauchy type equation 0.001025 _ A
n = 1.15436 -I- _
~
The temperature coefficient of the refractive index is -0.0004. Acknowledgments. The continued encouragement of H. H. Hyman and the staff a t Argonne National Laboratory is gratef Ltlly acknowledged.
prior to testing was carried out a t 400' for 6 hr. a t a flow rate of 100 cc. (STP) Hz/min. The hydrogen was purified bv passage through a "Deoxo" unit and over Linde 5A Molecular Sieves. The catalyst supports were commercial grades of Davison 11-alumina and Davison silica gel. They were calcined for 3 hr. at 500' prior to impregnation from aqueous solutions of nickel nitrate as described prev i o u ~ l y . ~The samples were oven-dried at 100' for 2 hr., then calcined a t 500' overnight. Supported cobalt, tungsten, and platinum catalysts were prepared in a similar manner using solutions of cobaltous nitrate and ammonium metatungstate, and a 10% solution of platinum chloride. The compositions and surface areas of these catalysts are listed in Tahle I. The decomposition of ammonia was determined by collecting portions of the desorbed gas and submitting for gas analysis.
Table I : Surface Area of the Metal-Promoted Alumina. Surface
Wt. 70 Metal
2 2 4 1
Nf
0 1 3 5 9
4 6 8 5 5
206 200 200 193 178
W
1 3 5 10 13
0 5 5 3 3
186 184 179 167 169
0 8
200 196
Ammonia A'dsorption on Rletal-.Promoted Catalyst Systems
by R. T. Barth and R. N. Pinchok Gulf Research d% Development Company, Pittsburgh, Pennsylvania (Received October 14,1968)
Experimental The ammonia adsorption technique was identical with that, described previously' except that reductioln
0 5 1 0
area, m.a/g.
20 1 199 199 194
co
The surface acidity of acid catalysts such as silicaalumina has been characterized by means of ammonia adsorption-desorption measurements.' Here the volume of ammonia adsorbed was measured as a function of the catalyst temperature, and the acid strength of the surface was determined from the relationship between catalyst temperature and the volume of adsorbed ammonia.2 This measurement has now been extended to include a series of supported metal catalysts. Alumina and silica were selected as the catalyst supports because of the distinct difference in their acid properties. The silica surface has approximately one-fifth the capacity for ammonia adsorption as the alumina surface. The metals used in this study included nickel, cobalt, platinum, and tungsten.
metal
Pt
18
Results The ammonia data obtained from met,al-alumina systems are presented in Fig. 1 and 2. The amount of ammonia chemisorbed a t 175' (the initial adsorption temperature) and 515' (the final desorption temperature) is plotted as a function of metal concentration. The results in Fig. 1 show the effect of nickel and co(1) R. T . Barth and E. V. Ballou, A n a l . Chem., 33, 1080 (1961). (2) A. N. Webb, I n d . Eng. Chem., 49, 261 (1959). (3) G. T. Rymer, J. M . Bridges, and J. R. Tomlinson, J . Phus. Chem., 65,2152 (1961).
Volume 68, AVumber S March, 1864
