Communications to the Editor
1480
currence of “normal” hot atom excitation-stabilization processes in liquid phase experiments.l*
Acknowledgments. We wish to acknowledge discussions with Professor D.L. Bunker and Drs. E.R. Grant and R.R. Pettijohn. Financial support has been provided by the U S . Atomic Energy Commission,13 from an N.D.E.A. Graduate Fellowship (R.G.M.), and from a John Simon Guggenheim Memorial Foundation Fellowship (J.W.R.).
2000
“E
1500
0
\ 0,
3 Y
z
q
References and Notes
0
(1) J. Franck and E. Rabinowitsch, Trans. Faraday SOC.,30, 120 (1934). (2) A. E. Richardson and R. Wolfgang, J. Am. Chem. Soc., 92, 3480 (1970). (3) M. 6. Loberg, K. A. Krohn, and M. J. Welch, J. Am. Chem. Soc., 95, 5496 (1973). (4) H. J. Machulla and G. Stocklin, J. Phys. Chem., 78, 658 (1974). (5) R. W. Helton, W. M. Grauer, and E. P. Rack, Radiochim. Acta, 19, 44 (1973). (6) We thank Professor A. E. Richardson for permission to reproduce the lBFvs. CH3F results. (7) We note that ref 3 and 4 have proposed caging mechanisms other than caged primary radical combination. For definition of this terminology cf. ref 8. (8) D. L. Bunker and B. S.Jacobson, J. Am. Chem. Soc., 94, 1843 (1972). (9) K. A. Krohn, N. J. Parks, and J. W. Root, J. Chem. Phys., 55, 5771, 5785 (1971). (IO) (a) R. G. Manning, Ph.D. Dissertation, University of California. Davis, 1975. (b) J. W. Root, US. Atomic Energy Commisslon Technical Report No. UCD-34P158-74-1, University of California, Davis, 1975. (c) R. G. Manning and J. W. Root, submitted for publication. (1 1) (a) For the close-packed sphere model the mean intermolecular separation is calculated as follows from the experimentally measured bulk density:
I
1000
I-
‘3 W
3 so0
0 IS
IO
5
0
2s
20
T I M E (rnin.) Flgure 1. Oxidation curves for Cu and NI at 700’ at 10 Torr of nitric oxide or oxygen. K1 is the rate constant for the linear rate law, Mg/ om2 min, and Kp is the rate constant for the parabolic rate law, pg2/cm4 mln.
X = [ B M / T ~ L ] ’X~ 108A in which the quantities M, p , and L denote molecular weight (amu), bulk density (g cm+), and Avogadro’s number, respectively. The molecular diameters employed in our calculations were determined from critical data (ref 1Ib): CHsF, 4.06; CF3CH3, 4.98; and CHF2CH3, 4.86 A. (b) J. W. Root, Ph.D. Dissertation, University of Kansas, 1964; Available from UniversityMicrofilms as Dissertation No. 65-7004. (12) (a) Evidence favoring secondary decomposition following T-for-H substitution in ilquid phase c - C ~ H has ~ been obtained previously (ref 12b,c). (b) E. K. C. Lee and F. S.Rowland, J. Am. Chem. Soc.,85, 897 (1963); (c) A. Hosaka and F. S.Rowland, J. Phys. Chem., 75, 3781 (1971). (13) This research has been supported under A.E.C. Contract No. AT-(043)34, project agreement 158.
Department of Chemistry and Crocker Nuclear Laboratory University of California Davis, California 956 16
Ronald G. Mannlng John W. Root’
Received February 24, 1975
Selective Oxidation of Nickel in Copper-Nickel Alloys in Nitric Oxide Publicationcosts assisted by YamaguchiUniversity
Sir: We found that nitric oxide (NO) selectively oxidized nickel in a Cu-Ni alloy, so that the structure of the scale formed on the alloy in nitric oxide was different from that formed in oxygen. Figure 1 shows the oxidation curves of copper and nickel plates in nitric oxide (700°, 10 Torr) and oxJyen (700°, 10 The Journal of Physical Chemistry, Voi. 79, No. 14, 1975
A
2
4
6
8
IO
12
14
16
3
TIME (min.) Figure 2. IMA spectrum of the scale on Cu-Ni alloy (35% Cu-65% Ni) formed at 700’ at 10 Torr of nitric oxide for 20 sec. The abscissa is the sputtering time by argon ions (7 kV for Nif and Cu+, 13 kV for 0-; 0.6 ~ A / 0 . 8 . m m ~ ) .
Torr) that were measured with a microbalance. On oxidation of these metals in nitric oxide, a linear rate law was observed, though a parabolic rate law was observed in oxygen.l More remarkable is the fact that the rate of the oxidation of nickel in nitric oxide was much higher than that of copper, while, in oxygen, the rate of the oxidation of nickel was very low compared to that of copper. These findings suggested that the oxidation of these metals in nitric oxide was related to the chemical reactivity of the surface species of the metals with nitric oxide, while that in oxygen was related to the diffusion behaviors of the metallic ions through the-oxide layers.2 Therefore, nickel should be preferentially oxidized on the oxidation of alloys of these metals in nitric oxide. Figures 2 and 3 show ion microanalysis (IMA) spectra of the scales on 35% Cu-65% Ni alloys formed in nitric oxide and oxygen, respectively. Then, the abscissa is the sputtering time by argon ions (7 kV for Ni+ and-Cu+, 13 kV for
I481
Communications to the Editor 12
1
Absolute Viscosity of D2’*0 between 15 and 35’
Sir: We have recently reported in this Journal1 values for the absolute viscosity of DzlsO between 15 and 35O. The values reported for the pure DzlBO were extrapolated from viscosity values determined for our experimental sample, whose composition is given in Table I , sample 1,by applying Eryring’s theory of viscosity 7 = ( h N / P )exp[AGt/RT] 0
2
4
6
8
IO
12
14
16
T I M E (min.)
Figure 3. IMA spectrum of the scale on Cu-Ni alloy (35% Cu-65% Ni) formed at 700’ at 10 Torr of oxygen for 20 sec.
0-; 0.6 pA/0.8 mm2). As seen in Figure 2 , the sputtered species almost entirely consisted of Ni+ and 0- in the initial stage of the sputtering on the scale by argon ions, and this signified the main component of the scale to be nickel oxide. On the other hand, in Figure 3, the amount of CU’ decreased rapidly with increasing sputtering time while that of Ni+ was found to have a maximum at 7 min after the beginning of the sputtering. The scale formed in oxygen seemed to consist of two distinct layers; Le., the component of the outer layer was copper oxide and that of the inner was nickel oxide. Then, the IMA spectra showed no evidence of nitrogen in these scales. The evaluations of the structures‘ of the scales by IMA spectra cited above were confirmed by means of X-ray diffraction analysis of the scale formed at 700’ at 10 Torr of nitric oxide for 30 min having given only the spectrum of NiO. However, the spectra of CuO and NiO were observed on X-ray diffraction patterns of the scale prepared in oxygen. Thus, it is remarkable that selective oxidation of nickel occurs in the oxidation of Cu-Ni alloy by nitric oxide. Acknowledgment. The authors wish to thank Mr. Masaharu Eguchi of the Faculty of Engineering, Osaka University, for obtaining the IMA spectra. References and Notes (1) Y. Takasu, Y. Matsuda, S. Maru, and N. Hayashi, Nature (London),submitted for publication. ( 2 ) C . Wagner, 2.fhys. Chem. 6, 32, 447 (1936).
Department of Industrial Chemistry Faculty of Engineering Yamaguchi University Tokiwadai, Ube 755 Yamaguchi, Japan
Yoshlo Takasu* Yoshiharu Matsuda Shun-lchi Maru Nobutoshl Hayashl
Department of Applied Chemistry Faculty of Engineering Osaka University Yamadakami, Suita 565 Osaka, Japan
Hlroshi Yoneyama Hldeo Tamura
where 7 is the viscosity, is the molar volume, and AGt is the free energy of activation for viscous flow. Due to the nature of the isotopic composition of the sample (i.e., the relatively high concentration of H atoms) we were faced with a major difficulty in the analysis of the experimental data. The hydrogen present exists essentially (-90%) in the form of HDO. Our extrapolation procedure requires viscosity and density values corresponding to the pure species of all components present in solution whereas pure HDO does not exist. I t exists only in solution and up to a concentration maximum of 50%. We simplified the analysis by neglecting the presence of the HDO species altogether and assumed that we were involved with a quarternary solution composed of H2160, H2180, D2160, and DzlSO. The mole fraction of each species was assumed to be the product of the mole fraction of its components. The validity of these assumptions was tested for a binary solution, Le., the viscosities of Hz160-Dz160 mixtures were calculated and compared to the experimental values available (cf. ref 1,Table V). We have lately been able to obtain a sample with much higher concentrations of deuterium and oxygen-18, as shown in Table I, sample 3. This enabled us to test the validity of the extrapolation technique and assumptions involved when applied to a “quarternary solution”. The isotopic analysis and the viscosity measurements of the highly enriched Dz180 sample 3 were performed using the identical apparatus as bef0re.l The viscosity values were extrapolated in the same manner to obtain those for pure Dzl*O. The experimental and extrapolated viscosity values are reported in Table I1 for sample 3 plus those for the two previously reported samples. We have included the data for the least enriched sample 2 to emphasize that the extrapolation is limited by the proximity to 100%purity, i.e., comDare A%(3 - 1) = 0.27 to A%(3 - 2) = 1.15, where A%(3 is the average difference between the extrapolated values
2
TABLE I: Isotopic Compositions of D2l80 Samples Sample 1
Received March 28, 1975
(1)
18
2 3
9i D
%H
9i 160
%
95.94 93.59 99.50
4.06 6.41 0.50
4.711 7.067 1.360
0.462 0.377 0.396
170
70
180
94.827 92.556 98.244
The Journal of Physical Chemistry, Vol. 79,No. 14, 1975
