817
V O L U M E 20, NO. 9, S E P T E M B E R 1 9 4 8 Table IV. 4nal)ses of Slnthetic Samples of Ternaries of n-Octane, a-Octene, Carbitol, and Ethylbenzene Compound Synthetic, ;c’ Calculated, R Difference r4 Carbitol n-Octane 2-Octene Carbitol n-Octane Ethylbenzene
47 18 34 37 25 37
4 0 6 5 0 5
47 17 35 37 25 37
1
G
3 2 3
i
-0 3 -0 4 0 7 -0 3 0 3 0 0
Table V. Analyses of Synthetic Samples of Ternaries Containing a Paraffin, an Unsaturate, and an Ox? genated Compound Cornpound Methylcyclohexane Methyl ethyl ketone Toluene Dichloroethyl ether n-Octane Ethylbenzene Cyclohexane Ethyl alcohol Benzene Hexanol n-Heptane Heptenes (mixture)
Synthetic, L ; 25 0 35 0 40 0 70.0 10 0 20.0 30.0 40.0 30.0 40.0 20.0 40.0
Calculated. % 24 G 34 7 40 7 68.7 10.9 20.4 30.7 39.4 29.9 40.3 21 . o 38.7
Difference -0 4 -0 3 0 7
‘1
-1 3 0 9
0 4 0.7 -0.6 -0.1 0.3 1.0 -1.3
Table TI. Analyses of Sj-nthetic Samples of Binarv Mixtures of 1leth:-l and Ethyl Alcohol Compound Synthetic., ‘6 Calculated, R Difference, 5% Methyl alcohol Ethyl alcohol 3Iethyl alcohol Ethyl alcohol
51.G 48.4 91.4 8.6
52.0 48.0 92.1 7.9
0.4 -0.4 0.7 -0.7
C-€I absorption region. Distinct bands near 3 . 4 0 ~for n-octarie are available but are not used, because the absorption there is too strong at the concentrations necessary to bring out adequate absorptions at the other n-ave lengths. The results for this system as well as those for a closely similar system in which the 2-octene is replaced by ethyl benzene may be seen in Table IT. In this latter system the difference of absorption intensity on the long ivave-length shouldm was again utilized.
In the preceding discussion ~tfew specific types of analyses found to be practical have been cnumerated and the results given on some synthetic miutures. The practicality of the method for such systems can best be determined after the absorption bands are automatically recorded. In Table lr are given a few more results on other systems for which the spectra will not be shown. In Table VI are given the results of tests on synthetic samples of binary mixtures of methyl and ethyl alcohol. The attainable accuracy depends upon the particular system being analyzed. The method has been found to give satisfactory results for almost all binary and ternary systems investigated. It is also suitable for the analysis of gas mixtures. I t considerably augments the usefulness of the absorption spectroscopic techniques in use at this laboratory and is noiy used as a routine procedure. The time required per sample is approximately the same, except for the dilutions, as for analyses by infrared when a sodium chloride prism and the longer ivave lengths are used. ACKNOWLEDGMENT
The authors wish to express acknowledgment to Paul D. Foote, executive vice president of Gulf Research and Development Company, for permission to publish this material. LITERATURE CITED
(1) Barnes, R. B., McDonald. R. S., ITillianis, Y.F., a n d K i n n a i r d , R. F., J . A p p l i e d Phys., 16, 77 (1947). ( 2 ) B r a t t a i n , R. R., Rasmussen, R. S., a n d C r a v a t h , il. XI.,I b i d . , 14, 418.(1943). (3) Coggeshall, N. D., R e z . Sei. I n s t r u m e n t s , 17, 343 (1946). (4) Coggeshall, X. D., a n d Saier, E. L., J . A p p l i e d P h y s . , 17, 450. (1946). Fox, J. J., a n d M a r t i n , -1. E., Proc. Roil. SOC.(London), 162, 419 (193’7).
I b i d . , 175,208 (1940). (7) Pauling, L., “Nature of t h e Chemical Bond,” Chap. I X , I t h a c a , N . Y . ,Cornel1 University Press, 1914. ( 8 ) Role, F.W., Bur. S t a n d a r d s J . Research, 20, 129 (1938). (9) TTi,ight, iY.,Rec. Sci.Instrummts, 15, 22 (1947). iCi)
I i t c t : ~ r zJanuary ~ 28, 1948.
Magnetic Stabilizer for Direct Current Arcs in Spectroscopy .
G. C. B. CAVE Provincial Department of Mines, Victoria, B. C . , Canada
I
T IS generally recognized that although the direct current arc is a versatile source of excitation, it provides relatively poor reproducibility when used for quantitative spectrochemical analyses. -4pparently this defect is due chiefly to wandering of the cathode “spot,” which produces both n-andering of the arc and fluctuations in amperage n-ith attendant changes in the discharge temperature. Ways of improving reproducibility are available. IIasler and Harvey (I), Jeppesen, Eastniond, and Logan (31, and others have described electrodes speciallv shaped for the purpose. .Jaycox and Ruehle ( 2 ) average the effects of wandering of the :ire by rotating the lower electrode holding the sample. llixiny the powdered sample with a “spectroscopic buffer” may improve reproducibility. Recentlj- Myers and Brunstetter ( 5 ) rwonimended a rotating magnetic field placed near the arc. The present paper describes a n instrument that eliminates almost completely the wandering of a central horizontal slice of the arc. Almost any part could be rendered free of fluctuations, but
in the present paper attention is directed only to that part from which the light is dispersed and photographed. PRINCIPLE OF THE INSTRUMEh-T
Sornially, a direct current arc is surrounded by a cricular magnetic field, depicted by broken circles in Figure 1. By reason of a well-known principle, placing one pole of a horizontal bar magnet near the arc 17-illcause the arc to m o w side!
