799
V O L U M E 24, N O . 5, M A Y 1 9 5 2 Table I\-.
Spectra” Resulting from Neutral and Singly Ionized .4toms Wave Length Region,
a
Elenient .4. c1 I b 4300-5218 c1 IIC 4300-5218 Br I 4300-5455 Br I1 4300-5455 I 1 4300-5500 I1 1300-5500 Lines classified in a term array. Neutral atom. Singly ionized atom.
h‘IIT Wave Length Tables, Lines 29 72 38 12 37 91
Lines Identified b y These Investigators 29 3 30 5 9 3
.4 complete reading of the halogen spectral lines deterxilined whether the spectra resulted primarily from neutral atoms or ionized atoms. B search of the MIT tables was conducted, with the data for each halogen being summarized as shown in Table IV. The unclassified lines listed in the tables were not compiled. From a theoretical standpoint’the elements with low ionization potentials should be excited and recorded much easier than the halogens which have high ionization potentials. However, throughout the course of this investigation the alkali metals sodium and potassium were conspicuous by their absence in the recorded spectra. ACKSOWLEDGMENT
tion it was extremely difficult t o maintain reproducible esperimental conditions. Consequently, it is the opinion of these investigators, on the basis of the experiments conducted and the equipment used, that quantitative analysis with an internal atandard is not practical with the high melting inorganic salts. A stronger escitation energ>-than the one used in this investigation would produce a more fully developed spark spectrum. With this excitation small variations of the experimental conditions would perhaps have no great influence on the intensity of the spectral lines. .I Pat isfactory quantitative analysk would then he powihle.
Appreciation is expressed to George Glockler for his espert guidance and to Harold Boaz for his helpful suggestions throughout this work. LITERATURE CITED
(1) Gatterer, A , , Spectrochina. Acta, 3, 214-33 (1948). (2) Gatterer, A., and Frodl, Y.,Ricerche spettroscop., 1, 201-44 (1946). (3) Harrison, G. R . , “M.I.T. Wax-elength Tables,” IYew York, John STiley & Sona, 1939. (4) Kiess, C. C., National Bureau of Standards, unpublished results. ( 5 ) Pearse, R. W. B., and Gaydon, A. G., “Identification of Molecular Spectra,” New Tork, John Wiley & Sons, 1941. R E C E I V E for D review August 2, 1951.
Accepted February 25. 1952
Optical Spectrophotometric Analysis of HydrogenDeuterium Mixtures in Presence of Air HERBERT P. BROIDi A S D GERRY H. 4IORG.4N .Yational Brirearc of Standards, Washington, D . C. The necessity for rapid, precise analysis of gaseous mixtures of hydrogen, deuterium, and air led to the adoption of the method of optical spectroscopy with photoelectric detection. An electrodeless discharge at 150 megacycles in a continuous flow gas system was used in conjunction with a high resolution photoelectric grating monochromator for these nieasurements. This pap& describes the system and the problems encountered in calibrating i t . Each of the components can be determined to better than 0.1% of the total mixtnre. .4determination can be
R
ELATIVELY little spectroscopic analysis of gaseous hgdrogen isotope mixtures has been attempted. Van Tiggelen (6) successfully analyzed hydrogen-deuterium mistures in the range 15 to 85% deuterium n i t h a precision of 2% of the minor component. He found an apparent preferential escitation of hydrogen. A preliminary survey ( 1 ) of the problem indicated the potentialities of a flowing gas system with a high frequency electrodeless discharge. For the Balmer lines, the measured ratio of peak deuterium line intensity to peak hydrogen line intensity ( D I H )was found to vary slightly with pressure and, to a lesser eutent, with intensity. The present work had several objectives: to determine optiniuni operating conditions for analyzing mixtures containing greater than 90% deuterium to an accuracy of a t least 0.5%; to arrive at a method of analysis of air present as an impurity; to determine the effect of such impurity on the deuteriuni analysis; and finally, to study further the effects on deuterium-hydrogen peak intensity ratio of pressure, discharge tube diameter, ex-
completed within 1 minute. ‘The effects on the measured intensities of \ arious experimental conditions are presented. The most striking effects are the small but continuous increase of deuteriumhydrogen line intensit! ratio with decreasing pressure and the dependence of this ratio upon Balmer transition. The Tarious effects noted may be of T alue to the theoretical inFestigation of highfrequency discharges. I n addition, the analytical method can probahl? he extended to include other gaseous and volatile mixtures.
citing frequency intensity, discharge cooling, and the particular line observed (Balmer 01, 8, or y ) . EQL’IPlIENT
The apparatus consists of three separate units-a mixing and flow system, a radio-frequency oscillator used for excitation, and a recording monochroniator. This equipment is essentially the same type as that used previously ( 1 ) . Figure 1 is a schematic diagram of the mixing and flow system. Hydrogen and deuterium are admitted to the 3-liter mixing chamber, C, through heated palladium valves, P H , and P D , , or a mixture is admitted directly from the sample bulb, S . Air is admitted through small capillary leak A . Pressure in C is read from the vacuum-type mercury manometer, iilc. The mixture flows through controlled-leak stopcock, SI, through one or a combination of fixed capillaries, F , whose pressure drop is measured by manometer A l p , and through one of the jacketed discharge tubes, J , having inner diameters of 2, 4, and 8 mm. Pressure in J is controlled by stopcock St, and is measured by the small mercury manometer, .UJ, or McLeod gage, G . IIei-
ANALYTICAL CHEMISTRY
8w cury diffusion pump P, backed by a mechanical forepump, continuously pumps the mixture through the system from the storage bulb, C , into the atmosphere. Traps T keep mercury and w a b r V R D O ~ S from t,he dischnrer t,uhea. Ballasts B help
Tahle I.
Precision of Method at Fixed Pressure, Flow Rate, and Mixture
(Pressure = 365 microns) [D/(D D H D/H S(D/H) Hj1100 90.03 9,033 -0,043 28.04 3.104 3.104 9.072 -0,004 90.07 28.16 28.28 3.112 9,087 +0.011 90.09 90.07 9.073 -0.003 28.20 3.108 90.06 28.24 3.116 9.062 -0.014 90.12 28.36 3.108 9,124 f0.048 3.112 9.074 -0,002 90.07 28.24 90.07 28.28 3.116 9.075 -0.001 3.108 fO.O1O 90.08 9.086 28.21 90.07 28.28 3.116 9.075 -0.001 9.076 90.075 A,.. *O.O%Z H"0t inesn sqiiare deviation
+
provided b; this oscnlator greatly aided the pr&ision of memu;: mlln+
Figure 2 is a photograph of the high resolution photoelectric grating monochromator (4),and accompanying electronic equipment, on field-trial loan to tho Nationel Bureau of Standards from Leeds and Northrup Co.
SID/(D H)l100 -0.04 - 0 01 +0.09 0.00 -0.02 +0.01 0.00
0.00
+o.oi
0.00
-10.02
The photomultiplier power supply is continuously variable from 45 t o 129 volts per stage. Combined with the stable linear direct current amplifier, this power supply gives a very wide range of sensitivity, making it possible to measure components of the gas mixture present in very small amounts. The output of the direct current amdifier is recorded by moans of a Leeds and
have been resolved. This'resalution is more than sufficient to resolve the hydrogen and deuterium isotope doublets whose separations are 1.8, 1.3, and 1.2 A. st Balmer a, 8, and y,, respectively. The eratine has Rowland ghosts with maxitnum i n t e n s t i e s 3 about 1 Dart in 200 of the main line. and has a t least twd series of such ghosts with separations of 1.2 and 2.7 A from the main line; hot,h series decsv rmidlv. ~n praOtic6 t
