Silas E. Gustafsson and Ernest Karawacki, "Refractive Index Measurements in Fused NaNO3 and KNO3 by a Modified Thermooptic Technique," Appl. Opt. 14, 1105-1110 (1975)
A thermooptic technique for studying the temperature dependence of refractive index of liquids at room temperature has been modified and applied to the study of molten NaNO3 and KNO3 within a temperature range of some 80 K above the melting point for five different wavelengths within the visible spectral range. The experiments show a temperature dependence of the polarizability for the two salts as calculated from the Lorentz-Lorenz formula, which cannot be explained by experimental inaccuracy.
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Refractive Index of Air for the 6328-Å Wavelengtha
Temp. °C
(nexp − 1) × 106
(next − 1) × 106
|nexp − next| × 106
19.3
269
272
3
27.2
261
265
4
35.4
254
258
4
46.1
246
249
3
56.1
238
242
4
67.2
230
234
4
78.4
222
226
4
92.6
214
217
3
105.8
206
210
4
122.2
198
201
3
139.0
190
193
3
158.1
182
184
2
177.7
174
176
2
201.3
166
168
2
226.4
158
159
1
258.2
150
150
0
289.8
142
141
1
340.6
134
130
4
383.2
126
121
5
435.8
118
112
6
A comparison between refractive indices extrapolated (next) with the Lorentz-Lorenz formula from earlier room temperature values and the experimental results (nexp) of this investigation.
Table II
Refractive index of Fused Quartz Herasil I Expressed by the Equation nl(t) = a0 + a1t + a2t2, where t is in °C.a
λ(Å)
N
a0
a1 × 105
a2 × 109
σ × 106
4765
45
1.463989
1.0411
4.673
2.8
4880
44
1.463263
1.0456
4.539
3.2
4965
47
1.462700
1.0440
4.473
2.7
5145
46
1.461694
1.0461
4.393
2.8
6328
33
1.457300
0.9966
4.337
3.4
A temperature range from 200°C to 500°C has been covered with the experiments. N is the number of experimental points, and σ is the standard error.
Table III
Refractive index of Molten NaNO3 Expressed by the Two Equations ns(t) = a + bt and ns(t) = a0 + a1t + ast2 where t is in °Ca
λ(Å)
N
a
−b × 104
σ × 105
a0
−a1 × 104
a2 × 108
σ × 105
4765
124
1.481895
1.4445
1.4
1.485114
1.6328
2.741
1.0
4880
121
1.480431
1.4376
1.8
1.486018
1.7644
4.759
1.1
4965
121
1.479377
1.4396
1.2
1.479797
1.4045
0.368
1.2
5145
114
1.477293
1.4383
1.8
1.480003
1.5970
2.316
1.3
6328
101
1.468581
1.4232
1.6
1.471192
1.5745
2.182
1.2
Temperature interval 310°C to 390°C. N is the number of experimental points, and σ is the standard error.
Table IV
Refractive index of Molten KNO3 Expressed by Two Equations ns(t) = a + bt and ns(t) = a0 + a1t + a2t2, where t is in °Ca
λ(Å)
N
a
−b × 104
σ × 105
a0
−a1 × 104
a2 × 108
σ × 105
4765
177
1.475786
1.5744
1.5
1.478201
1.7016
1.665
0.9
4880
172
1.474426
1.5740
1.5
1.476863
1.7021
1.675
0.7
4965
170
1.473472
1.5698
1.5
1.474948
1.6473
1.013
1.1
5145
164
1.471528
1.5656
1.0
1.472543
1.6191
0.699
0.8
6328
73
1.464045
1.5635
2.3
1.476987
2.2824
9.964
2.0
Temperature interval 340°C to 420°C. N is the number of experimental points, and σ is the standard error.
Table V
Temperature and Frequency Dependence of the Molar Refractivity of Molten NaNO3 Calculated from the Lorentz-Lorenz Equation
T(°C)
4765 Å
4880 Å
4965 Å
5145 Å
6328 Å
∞
310
11.702
11.668
11.646
11.597
11.405
11.037
330
11.722
11.688
11.666
11.618
11.424
11.053
350
11.742
11.709
11.687
11.638
11.443
11.070
370
11.764
11.730
11.707
11.659
11.462
11.087
390
11.786
11.753
11.727
11.680
11.482
11.104
Table VI
Temperature and Frequency Dependence of the Molar Refractivity of Molten KNO3 Calculated from the Lorentz-Lorenz Equation
T(°C)
4765 Å
4880 Å
4965 Å
5145 Å
6328 Å
∞
340
13.761
13.722
13.700
13.648
13.436
13.032
360
13.778
13.739
13.717
13.665
13.450
13.042
380
13.796
13.757
13.734
13.681
13.465
13.057
400
13.814
13.774
13.751
13.699
13.483
13.076
420
13.832
13.792
13.769
13.716
13.503
13.100
Tables (6)
Table I
Refractive Index of Air for the 6328-Å Wavelengtha
Temp. °C
(nexp − 1) × 106
(next − 1) × 106
|nexp − next| × 106
19.3
269
272
3
27.2
261
265
4
35.4
254
258
4
46.1
246
249
3
56.1
238
242
4
67.2
230
234
4
78.4
222
226
4
92.6
214
217
3
105.8
206
210
4
122.2
198
201
3
139.0
190
193
3
158.1
182
184
2
177.7
174
176
2
201.3
166
168
2
226.4
158
159
1
258.2
150
150
0
289.8
142
141
1
340.6
134
130
4
383.2
126
121
5
435.8
118
112
6
A comparison between refractive indices extrapolated (next) with the Lorentz-Lorenz formula from earlier room temperature values and the experimental results (nexp) of this investigation.
Table II
Refractive index of Fused Quartz Herasil I Expressed by the Equation nl(t) = a0 + a1t + a2t2, where t is in °C.a
λ(Å)
N
a0
a1 × 105
a2 × 109
σ × 106
4765
45
1.463989
1.0411
4.673
2.8
4880
44
1.463263
1.0456
4.539
3.2
4965
47
1.462700
1.0440
4.473
2.7
5145
46
1.461694
1.0461
4.393
2.8
6328
33
1.457300
0.9966
4.337
3.4
A temperature range from 200°C to 500°C has been covered with the experiments. N is the number of experimental points, and σ is the standard error.
Table III
Refractive index of Molten NaNO3 Expressed by the Two Equations ns(t) = a + bt and ns(t) = a0 + a1t + ast2 where t is in °Ca
λ(Å)
N
a
−b × 104
σ × 105
a0
−a1 × 104
a2 × 108
σ × 105
4765
124
1.481895
1.4445
1.4
1.485114
1.6328
2.741
1.0
4880
121
1.480431
1.4376
1.8
1.486018
1.7644
4.759
1.1
4965
121
1.479377
1.4396
1.2
1.479797
1.4045
0.368
1.2
5145
114
1.477293
1.4383
1.8
1.480003
1.5970
2.316
1.3
6328
101
1.468581
1.4232
1.6
1.471192
1.5745
2.182
1.2
Temperature interval 310°C to 390°C. N is the number of experimental points, and σ is the standard error.
Table IV
Refractive index of Molten KNO3 Expressed by Two Equations ns(t) = a + bt and ns(t) = a0 + a1t + a2t2, where t is in °Ca
λ(Å)
N
a
−b × 104
σ × 105
a0
−a1 × 104
a2 × 108
σ × 105
4765
177
1.475786
1.5744
1.5
1.478201
1.7016
1.665
0.9
4880
172
1.474426
1.5740
1.5
1.476863
1.7021
1.675
0.7
4965
170
1.473472
1.5698
1.5
1.474948
1.6473
1.013
1.1
5145
164
1.471528
1.5656
1.0
1.472543
1.6191
0.699
0.8
6328
73
1.464045
1.5635
2.3
1.476987
2.2824
9.964
2.0
Temperature interval 340°C to 420°C. N is the number of experimental points, and σ is the standard error.
Table V
Temperature and Frequency Dependence of the Molar Refractivity of Molten NaNO3 Calculated from the Lorentz-Lorenz Equation
T(°C)
4765 Å
4880 Å
4965 Å
5145 Å
6328 Å
∞
310
11.702
11.668
11.646
11.597
11.405
11.037
330
11.722
11.688
11.666
11.618
11.424
11.053
350
11.742
11.709
11.687
11.638
11.443
11.070
370
11.764
11.730
11.707
11.659
11.462
11.087
390
11.786
11.753
11.727
11.680
11.482
11.104
Table VI
Temperature and Frequency Dependence of the Molar Refractivity of Molten KNO3 Calculated from the Lorentz-Lorenz Equation
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