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).
