A mounting for two photomultiplier tubes for the Baird spectrograph is described. Leeds and Northrup experimental preamplifiers and ratio recorder are used in conjunction with the photomultipliers. The 60-cycle ac signal system is described. The equipment has been used in three analytical problems: the determination of Li in the flame, uranium isotopic determinations using the hollow cathode and the spark, and the copper spark determination of scandium. The precision of the uranium isotopic determination is discussed.
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Sample A was a synthetic mixture of uranium oxides which was made to contain 3.70 percent U235.
Calculated according to the method of least squares
, where r0=probable error in average, v=deviation from average, and n=number of traces.
Table VI
Uranium isotopic determinations. Comparison of optical spectrographic results using spark excitation with mass spectrographic results.
Results (percent) U235
Sample No.
Opt. spect.
Mass spect.
Uncertainty mass spect.
Deviation
19986
93.5
93.7±0.12
0.2
19987
93.6
93.93±0.05
0.3
19988
93.4
93.37±0.07
0.0
19989
93.5
93.34±0.05
0.2
19990
93.4
93.47±0.05
0.1
19991
93.4
93.54±0.05
0.1
19992
93.5
93.93±0.05
0.4
19993
92.9
93.31±0.05
0.4
19994
93.6
93.83±0.12
0.2
19995
93.2
93.48±0.05
0.3
19997
93.1
93.36±0.09
0.3
19998
92.8
93.15±0.06
0.4
19999
93.6
93.94±0.05
0.3
20000
93.4
93.23±0.10
0.2
20001
93.9
93.96±0.05
0.1
20002
93.8
93.9±0.05
0.1
20004
93.1
93.93±0.07
0.8
20005
93.3
93.2±0.05
0.1
0.25
Table VII
Uranium isotopic determination intensity data for 10 consecutive traces.
Intensities
Deviation from average
Isotope
Line I +bkgd I
Bkgd I
Line I
Line I
Total
F238
U235
0.662×5
0.050×5
0.612×5
3.060
3.290
0.0699
0.0005
U238
0.430
0.200
0.230
0.230
U235
0.670×5
0.050×5
0.620×5
3.10
3.338
0.0713
0.0009
U238
0.430
0.192
0.238
0.238
U235
0.660×5
0.048×5
0.612×5
3.060
3.295
0.0713
0.0009
U238
0.430
0.195
0.235
0.235
U235
0.660×5
0.050×5
0.610×5
3.050
3.280
0.0701
0.0003
U238
0.430
0.200
0.230
0.230
U235
0.660×5
0.050×5
0.610×5
3.050
3.282
0.0707
0.0003
U238
0.430
0.198
0.232
0.232
U235
0.660×5
0.050×5
0.610×5
3.050
3.280
0.0701
0.0003
U238
0.430
0.200
0.230
0.230
U235
0.668×5
0.05×5
0.618×5
3.090
3.320
0.0693
0.0011
U238
0.430
0.200
0.230
0.230
U235
0.666×5
0.050×5
0.616×5
3.080
3.312
0.0700
0.0004
U238
0.432
0.200
0.232
0.232
U235
0.662×5
0.05×5
0.612×5
3.060
3.297
0.0719
0.0016
U238
0.435
0.198
0.237
0.237
U235
0.672×5
0.044×5
0.628×5
3.140
3.373
0.0691
0.0013
U238
0.425
0.192
0.233
0.233
Average
0.0704
0.00076
Tables (7)
Table I
Photomultiplier operating conditions for determination of lithium.
Element
Wavelength (A)
Tube type
Volts per dynode
Anode voltage
Exit slit width (microns)
Entrance slit width (microns)
Li
6706.84
1P28
75
75
100
200
Co
3529.81
1P28
60
60
300
200
Table II
Spectrographic and chemical determinations of lithium (mg/ml).
Sample No.
Chemical results
Spec. results
Difference
72B
0.0372
0.0363
0.0009
75B
0.0368
0.0378
0.0010
82B
0.0349
0.0353
0.0004
83B
0.0372
0.0378
0.0006
85B
0.0350
0.0355
0.0005
17158
0.0383
0.0384
0.0001
17168
0.0383
0.0384
0.0001
17174
0.0363
0.0358
0.0005
Average difference
0.0005 mg/ml
Table III
Reproducibility of the spectrographic results.
Sample No.
Li concentration (mg/ml) determination
Average (mg/ml)
Deviation from average (mg/ml)
1
2
19017
0.0683
0.0681
0.0682
0.0001
19039
0.0646
0.0638
0.0642
0.0004
19040
0.0653
0.0645
0.0649
0.0004
19051
0.0671
0.0665
0.0668
0.0003
19052
0.0671
0.0677
0.0674
0.0003
19053
0.0687
0.0699
0.0693
0.0006
19054
0.0684
0.0695
0.0689
0.0006
19055
0.0595
0.0604
0.0600
0.0004
19056
0.0682
0.0686
0.0690
0.0004
19057
0.0685
0.0669
0.0677
0.0008
19058
0.0659
0.0648
0.0653
0.0005
19059
0.0645
0.0642
0.0643
0.0001
19060
0.0683
0.0678
0.0680
0.0002
19061
0.0674
0.0665
0.0669
0.0004
19062
0.0684
0.0686
0.0685
0.0001
Average deviation from average
=0.0004 mg/ml
Average deviation (in % amount present)
=0.60%
Table IV
Uranium isotopic determination. Comparison of optical spectrographic results using hollow cathode excitation with mass spectrographic results.
Percent U235
Sample No.
Optical spec.
Mass spec.
1
93.3
93.26±0.05
2
93.3
93.2±0.1
3
93.2
93.16±0.05
4
93.3
93.2±0.1
5
93.2
93.3±0.2
6
93.4
93.3±0.1
Table V
Reproducibility of uranium isotopic determinations using hollow cathode excitation.
Sample A was a synthetic mixture of uranium oxides which was made to contain 3.70 percent U235.
Calculated according to the method of least squares
, where r0=probable error in average, v=deviation from average, and n=number of traces.
Table VI
Uranium isotopic determinations. Comparison of optical spectrographic results using spark excitation with mass spectrographic results.
Results (percent) U235
Sample No.
Opt. spect.
Mass spect.
Uncertainty mass spect.
Deviation
19986
93.5
93.7±0.12
0.2
19987
93.6
93.93±0.05
0.3
19988
93.4
93.37±0.07
0.0
19989
93.5
93.34±0.05
0.2
19990
93.4
93.47±0.05
0.1
19991
93.4
93.54±0.05
0.1
19992
93.5
93.93±0.05
0.4
19993
92.9
93.31±0.05
0.4
19994
93.6
93.83±0.12
0.2
19995
93.2
93.48±0.05
0.3
19997
93.1
93.36±0.09
0.3
19998
92.8
93.15±0.06
0.4
19999
93.6
93.94±0.05
0.3
20000
93.4
93.23±0.10
0.2
20001
93.9
93.96±0.05
0.1
20002
93.8
93.9±0.05
0.1
20004
93.1
93.93±0.07
0.8
20005
93.3
93.2±0.05
0.1
0.25
Table VII
Uranium isotopic determination intensity data for 10 consecutive traces.