NOTES
Jan., 1961
183
P
18(600)-1541. Reproduction in whole or in part is permitted for any purpose of the United States Government. COMPRESSIBI LITIES AND ISOCHORES OF (C3F7COOCH2)*C,C - S ~ , O ~ ( C Hn-C;H12, ~ ) ~ , n-C8Hl8, %%4-CdH,(CH3)3, C-CjHlo, C-C6I12, c - C ~ H ~ C H S , CsHjCH3, p-C&(CH3)2, s - C ~ H ~ ( C H ~CH2CL ), BYKOzO SIIINODA~ AND J. H. HILDEBRAND Department of ('hemzstrji, Uniuerszty of Californza, Berkeley, California Received July 6 , 1960
The measurements herein reported were made primarily in order to have data for evaluating the contribution of expansion to the entropy of solution, the magnitude of which has been emphasized in recent studies.'2 The apparatus used is shown in Fig. 1. The bulb had a capacity of 35.33 cc. The volume of the capillary stem was 0.00399 cc. per cm. A liquid was cooled, well degassed, and introduced into the evacuated bulb. A small amount of mercury was introduced to confine the liquid. A series of three or more pressures ranging from 0.3 to 2.2 atm., mas applied to the capillary and the jacket. The temperature was controlled to within O.O0lo; 2 to 4 hours were allowed to attain equilibrium. Correction was made for the compressibility of Pyrex. In this range, AB vs. AP was strictly linear within the limits of error, therefore our figuresfor compressibility are essentially @ = - ( b In V / b P ) r . The liquids were all carefully purified. We estimate an accuracy within I per cent. The results are given in Table I together with, for
Fig. 1.
and Andrew@ found 0.934 and Tyrer4 found 0.941, both from adiabatic compressibility. Our figure is in excellent agreement. This work has been supported by the Atomic Energy Commission. (3) E. B. Freyer, J. C. Hubbard and D. H. Andrews, J . A m . Chsm. SOC.,51, 759 (1929). (4) D. Tyrer, J . Chem. Soc., 103, 1675 (1913).
MASS DEPENDENT ION COLLECTION EFFICIENCIES I N A MASS
TABLEI UNITS:ATMOS.,Cc., MOLE,25" (CaF7COOCHz)aC c-SLO~CHS)B n-CsH1z n-CaHls 2,2,4-CaHe(CH3)3 c-CsHio c-CaHi, c-C~HIICH~ CsHdX I)-CSH~(CHS)Z s-CsH,(CH3)3 CHzClz
I
1048
Vol. per mole
( b P / aT ) ,
1.06 1.56 2.17 1.35 1.58 1.37 1.15 1.18 0.93 0.92 0.88 1.09
541.5 312.2 116.1 163.5 166.1 94.7 108.7 128.3 106.9 123.9 139.6 64.5
9.28 7.96 7.65 8.52 7.63 9.71 10.5 9.6 11.5 11.1 10.7 12.4
SPECTROMETER' BY DONA. KUBOSEAND WILLIAM H. HAMILL Department of Chemistry, The Univereity of Notre Dame, Notre Dame Indiana Received July 1 1 , 1960
Calculations of gaseous ion-molecule reaction cross sections Q from mass spectrometric measurements require a knowledge of the primary and secondary ion currents, I p and Is, the length of primary ion path, 1, through the reacting gas M and the concentration n M . These are related by equation 12*3 =
I$(IPhM)
-1
(1)
convenience,molal volumes, and liquid isochores calculated by the re1,ation:
The validity of this equation depends upon equal collection efficienciesfor the primary and secondary ions. Differences arising from mass dependent ( ~ P I B T=) ~ -(a In v/aT)p/(a In v/ap)T discrimination in the slit systems are negligible in These figures serve to calculate other important the present context except at lower masses and can thermodynamic functions, e.g., (bE/bV)T and (bX/ be ~alculated.~This still leaves unsettled the bv)T . (1) Contribution from the Radiation Projeot of the University of The only liquid in the table for which we find refDwae, supported in part under AEC Contract AT(ll-1)-38. erences for @ is CeH&Hs, for which Freyer, Hubbard Notre (2) D, P. Stevenson and D. 0. Sohissler, J . Chem. Phya., W , 1353 (1) Department of Chemistry. Faculty of Engineering, Yokohama National University, Ohka-Machi, Minami Ku. Yokohama, Japan. (2) J. H. Hildehrand, T H I JOURNAL, ~ 84, 370 (1960); K. Shinoda and J. Ii. Hiidebrand, ibid., 61, 789 (1967).
(1955). (3) F. H. Field, J. L. Franklin and F. W. Lampe, J . Am. Ch6m. Soc., 74, 2419 (1957). (4) N. Cogowhall, J . Chrm. Phyo.. 12, 19 (1944).
184
Voi. 6:
KOTES
TABLE I
RATIOO F ANALYZED
IS
ION CURRENT TO 4 15.5
m/e Er(v./cm.)
2
12 20 28 40 60 80
1. L8
1.16
1.14 1.11
1.13
1.11 1.11
1.09
1.05
1.04
1.11
1.09
0.98 .94 .95 .95 .96 .97
TOTAL ION 18.9
0.96 .95 * 93 .94 .95 .96
C U R R E N T It A T V A R I O U S n l / e ,
33.1
40
83.7
131.3
1.06
0.97 .96 .94 .94 .94 .95
1.06 1.03
0.99 .96 .95 .95 .95 .94
1.04 1.02 1.02 1.00 1.oo 0.99
1.00 1.00 1 .00 1.00 1.00 1 .oo
1.02 1 .oo 1.00 1.00 1.00
Experimental These experiments were performed with a CEC model 21-103A mass spectrometer with a model 31-402 ion source. The repeller to exit slit electrode spacing is 0.25 cm. with the electron beam nearly midway between them. The electron ionizing current was 10.5 Ma., the ionizing voltage was 60 v. and the reservoir pressure was 300 p throughout. The ion accelerating voltage waa 1230 v. f 5% for all m/e. The m/e interval of interest w&8 scanned electrostatically. Measurements of I. were made a t several repeller voltages. Total positive ion current in the ionization chamber of the mass spectrometer was always measured by connecting both repeller electrodes to ground through the input resistance of a vibrating reed electrometer, using a 22.5 v. bias, corresponding to a field of 90 v./cm. Gases used were H2,.Dl, CHI, CD4,.Ne, CzHz, I+S, Ar, Kr and Xe. They contained only neghgible impurities. For nob!e gases the I J I t ratios are taken a t the average m/e (weighted by rtbundances) for the singly charged isotopic ions. For methane, the weighted average of the m/e 13, 14, 15 and 16 ions was used. For methane-&, the weighted average of m/e 14, 16, 18 and 20 was used. For CZHzand HzS, m/e 24, 26, 26, 27 and m/e 32, 33, 34, 35, 36, respectively, were used. Ion abundame curves were determined for AT+, AT++, Kr+, Kr++and Xe+, Xe++a t E, = 12 v./cm. repeller field strength.
Results The total ion current measured for the noble gases was corrected for the appreciable contributions from dloubly charged ions of argon, krypton and In each instance the effect of repeller field upon electron energy was allowed for. The corrected total ion current was taken as Is+ It/ (Ia+ IB++). Analogously for CH4, CD4, C2H2 and H2S the corrected total current becomes IaIt/ D. 0. Sohider, ibid., ZiS, 282 (1958). (13) W. Bleakney, P h w . Qn.,86, 1303 (1930). (7) J. T. Tate iind P. T. Bmith, ibid., 46, 773 (1934). (5) D. P. Stevenson and
XENON
25.7
question whether any other effects contribute to discrimination among ions at different mle, and between primary and secondary ions which originate in different regions of the ionization chamber. In previous studies of ion-molecule reactions this possible Source of error has not been adequately accounted for, although Stevenson and Schissler6 used H2+, H D + and D2+to establish an empirical correction for mass dependent discrimination in the corresponding interval of m/e. This report describes an experimental approach to the problem which only requires comparing the ratio of the analyzed ion current, Is, measured conventionally at given m/e to the total saturation current, It, measured on the negatively biased repeller electrodes. If ions appear over an appreciable range of m/e, then it is evidently required that for some one ion species k,I& >> Z a i . The noble gases meet this requirement best and some molecular gases are also acceptable.
+
NORMALIZED TO UNITY FOR
20.2
1.01 1.02 1.01
1.02
ZIai where the summation applies to all ionic species. The results, which appear in Table I, cover the useful range of repeller fields. In the m/e region investigated there is little discrimination (in the instrument used) for any repeller field except for a small increase at low m/e. Our concern with this problem is primarily to establish conditions for distinguishing among various possible ion-molerule force laws and reaction rate expressions.
A COMPARISON OF THE MEASUREMENT OF HEATS OF ADSORPTION BY CALORIMETRIC AND CHROMATOGRAPHIC METHODS ON THE SYSTEM NITROGEN-BONE MINERAL BY R. A. BEE BE^ AND P. H. EMMETT Departments of Chemistry, Amherst College, Amherst. Maasachusetts and Johns Hopkins Uniuerszty, Baltimore, Maryland Received J d r 18, 1880
Several investigation^^-^ reported in the literature have been concerned with the determination of heats of adsorption from the retention times obtained in gas-solid chromatography. However, in none of this work has it been possible to make a direct comparison between the heat values derived from chromatography and the heats measured calorimetrically for the same adsorption system. As a part of a program of adsorption studies on bone mineral in the Amherst laboratory, calorimetric data are available for the differential heats of adsorption of nitrogen at 195" on this adsorbent. These data will be submitted in the near future for publication in detailed form. In the Johns Hopkins laboratory we have determined the retention times for nitrogen pulses in helium carrier gas over a column of the bone mineral. Thus we are in a position to compare the heat values determined by the two methods.
-
The bovine bone mineral supplied by the Armour Research Laboratories, designated as OSSAR, consisted of granules of 20-40 mesh which proved to be a convenient form for use in both the calorimetric and the chromatograpkc work. A considerable amount of information on. the adsorption characteristics of water, methanol and nitrogen on this material are given in a recent paper.6 The OSSAR was (1) One of us (R.A.B.) expresses appreciation to the Petroleum Research Foundation for fellowship aid which made it possible to spend the academic year 1959-1960 in the laboratories of Johns Hopkins University and the University of Bristol. (2) E. Cremer and F. Prior, 2. Elpktrochcm., 66, 66 (1951). (3) 9. A. Greene and H. Pust, THIB JOURNAL,62, 55 (1958). (4) H. W. Habgood and J. F. Hodan, Can. J . Cham.. W. 843
(1959). ( 5 ) h.I. E. Dry and It. A. Beebe. THIBJOURNAL, 64, 1300 (1960).
