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Study of temperature and concentration dependence of refractive index of liquids using a novel technique

  • February 2006
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Deepak Prasad Subedi at Kathmandu University
Deepak Prasad Subedi
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A simple and reliable method of measuring the refractive index of liquids is reported in the present paper. The technique was employed to study the temperature dependence of refractive index of water (at sodium D-line 589nm). By measuring the refractive index of water at different temperatures, the temperature coefficient of refractive index (dn/dT) was determined. In addition to this, refractive index of different solutions as a function of the concentration was studied. The results were compared with the results obtained from commercial refractometers and it was found that this technique is quite reliable and can be safely used in the study of the optical properties of any transparent liquids
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KATHMANDU UNIVERSITY JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY
VOL.II, No.1, FEBRUARYR, 2006.
STUDY OF TEMPERATURE AND CONCENTRATION DEPENDENCE OF
REFRACTIVE INDEX OF LIQUIDS USING A NOVEL TECHNIQUE
Subedi, D.P., Adhikari, D.R., Joshi, U.M., Poudel, H. N., Niraula, B.
Department of Natural Sciences,
Kathmandu University, Dhulikhel, Kavre, P.O. Box: 6250, Kathmandu, Nepal.
Corresponding Author E-Mail: deepaksubedi2001@yahoo.com
ABSTRACT
A simple and reliable method of measuring the refractive index of liquids is reported in
the present paper. The technique was employed to study the temperature dependence of
refractive index of water (at sodium D-line 589nm). By measuring the refractive index of
water at different temperatures, the temperature coefficient of refractive index (dn/dT)
was determined. In addition to this, refractive index of different solutions as a function of
the concentration was studied. The results were compared with the results obtained from
commercial refractometers and it was found that this technique is quite reliable and can
be safely used in the study of the optical properties of any transparent liquids
INTRODUCTION
Refractive index is one of the most important optical properties of a medium. It plays
vital role in many areas of material science with special reference to thin film technology
and fiber optics. Similarly, measurement of refractive index is widely used in analytical
chemistry to determine the concentration of solutions. Recent studies [Schwartz 1999,
Olesberg 2000, Shlichta 1986] provide more detailed discussion on the concentration
mapping by the measurement of refractive index of liquids. Temperature coefficient of
refractive index can also be used to calculate thermal expansion coefficient [Miller 1975].
Several techniques are reported in literature for the measurement of concentration and
temperature dependence of refractive index of liquids [McPherson 1999, Garcia 1999,
Otalora 1999, Miyashita 1994]. The present paper reports a relatively simple and effective
technique, which can be used to measure the refractive index of the liquid at different
temperatures.
The absolute refractive index of a medium is the ratio of the speed of electromagnetic
radiation in free space to the speed of the radiation in that medium. The relative refractive
index is the ratio of the speed of light in one medium to that in the adjacent medium.
Refraction occurs with all types of waves but is most familiar with light waves. The
refractive index of a medium differs with frequency. This effect, known as dispersion,
lets a prism divide white light into its constituent spectral colors. For a given color, the
refractive index of a medium depends on the density of the medium, which on the other
hand is a function of temperature. By measuring the refractive indices at different
temperatures, the temperature coefficient of refractive index (dn/dT) can be determined.
MATERIAL AND METHOD
A convenient formula for refractive index, n, can be obtained in the minimum deviation
case when a ray of light suffers deviation while passing through a prism. The deviation
produced by the prism depends on the angle of incidence. For a certain value of the angle
of incidence, the angle of deviation is minimum. If Dm denotes the angle of minimum
1
KATHMANDU UNIVERSITY JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY
VOL.II, No.1, FEBRUARYR, 2006.
deviation for a given prism of refractive angle A, then the refractive index of the material
of the prism n is given by,
+
=
2
A
sin
2
DA
sin
n
m
................ (1)
Equation (1) has been employed to calculate the refractive index of the liquids.
Experimental arrangement used in our study is depicted in Fig. 1. Specially constructed
hollow prism was used to measure the refractive index of liquids with the help of an
optical spectrometer. A monochromatic source of light (sodium lamp) was used and a
collimated beam was allowed to fall on one reflecting face of the liquid prism and the
angle of minimum deviation was determined for yellow light (at sodium Dline 589 nm).
Mean of two values were taken for each angle of minimum deviation. For the
measurement of refractive index at different temperature, the liquid was heated up to
80°C and poured into the hollow prism and the angle of minimum deviation was
measured at different temperatures of the cooling liquid. A thermometer was inserted in
the liquid avoiding the path of light being observed.
To study the variation of refractive index of salt solutions as a function of concentration,
an electronic balance weighed salts and solutions of required concentrations were
prepared by dissolving the salts in 100 ml of water. Thus prepared solutions were filtered
before pouring into the hollow prism. The hollow prism was rinsed carefully after every
measurement. Solutions of lower concentrations (20%, 10%, 5%, 2.5% and 1.25%) were
made by diluting the solutions with equal volume of water.
RESULTS AND DISCUSSION
Effect of Temperature on Refractive Index of Water
The refractive index of water as a function of temperature is depicted in Fig 2. The result
shows a linear dependence of refractive index of water on temperature in the range 30°C-
70°C. By applying data analysis program the experimental data were subjected to curve
fitting and the temperature coefficient of refractive index of water was found to be equal
to − 1.853 × 10−4/C. For highly accurate measurements, the optical constants of the glass
container should also be taken in account because the light will pass through both the
solution and the container. According to the literature [Lukin 1993], the temperature
coefficient of refractive index of glass is of the order of 10−4/C. It is evident that very
small error can occur if the temperature dependence of the refractive index of glass is not
taken into account while measuring the temperature coefficient of refractive index of
liquids.
Effect of Concentration
2
KATHMANDU UNIVERSITY JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY
VOL.II, No.1, FEBRUARYR, 2006.
Fig.1 Experimental set-up for the measurement of refractive index by an optical
spectrometer.
Refractive index of common salt solution as a function of concentration is depicted in
Fig. 3. For 20% solution, refractive index is as high as 1.358, which reduces to 1.331
when the solution is diluted to a concentration of 1.25%. With the decrease in
concentration, the density of the solution also decreases resulting a decrease in refractive
index. The results showed that the refractive index of the solution of concentration less
than 2.5% measures nearly the same as that of the pure water. The result indicated that the
effect of concentration on refractive index is dominant up to the concentration of 5%.
After that there is weak dependence of concentration of refractive index. Fig. 4 shows a
similar result for sugar solution. As the solubility of sugar is high, the measurements were
performed up to 40% concentration of the solution. The refractive index of the sugar
solution was found to be 1.387 for 40% solution. The value reduces to 1.332 when the
concentration was reduced to 2.5%. In contrast to the result of salt solution, the effect of
concentration is strong up to 20% concentration of the sugar solution. However, after this
value the dependence becomes weak.
Fig 5, 6 and 7 depict the dependence of refractive index of propanol_1, sucrose and
potassium chloride solution on their concentration respectively. A comparison is made
between the results obtained from our measurement and the values mentioned in literature
[http://www.mt.com]. It is evident that our results are in agreement with the literature
value so far as the nature of variation is concerned. Repeating the experiment checked the
value of refractive index of propanol_1 solution of 20% concentration with higher
deviation. Similarly, refractive index of sucrose solution of concentration 10% was
measured twice (indicated by error bar). In the same way for potassium chloride, the
experiment corresponding to 10% and 20% concentrations were repeated.
3
KATHMANDU UNIVERSITY JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY
VOL.II, No.1, FEBRUARYR, 2006.
30 40 50 60 70 80
1.331
1.332
1.333
1.334
1.335
1.336
1.337
1.338
1.339
dn/dT = -1.853 x 10-4
Temperature (C)
Refractive index (n)
Fig 2 Temperature dependence of refractive index of water.
0 5 10 15 20
1.330
1.335
1.340
1.345
1.350
1.355
1.360
Common Salt Solution
Refractive index (n)
Concentration (%)
Fig. 3 Refractive index of sodium chloride solution as a function
o
f i
ts
co
n
ce
n
t
r
at
i
o
n
e
x
p
r
essed
in
pe
r
ce
n
tage.
4
KATHMANDU UNIVERSITY JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY
VOL.II, No.1, FEBRUARYR, 2006.
0 10203040
1.32
1.33
1.34
1.35
1.36
1.37
1.38
1.39
1.40
Refractive index (n)
Concentration (%)
Sugar solution
Fig. 4 Refractive index of sugar solution as a function o
f
its concentration expressed in percentage.
0 5 10 15 20 25 30 35 40 45
1.335
1.340
1.345
1.350
1.355
1.360
1.365
Propanol_1
Current Technique (24C)
Literature value (20 C)
Refractive Index (n)
Concentration (%)
Fig. 5 Refractive index of Propanol_1 as a function of
concentration measured by the present technique and obtained
from literature.
5
KATHMANDU UNIVERSITY JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY
VOL.II, No.1, FEBRUARYR, 2006.
Fig. 6 Refractive index of sucrose as a function of
concentration measured by the present technique and
obtained from literature.
Fig. 7 Refractive index of potassium chloride as a function of
Concentration measured by the present technique and obtained from
literature.
CONCLUSION
We have been able to design a hollow prism suitable for the measurement of refractive
index of transparent liquids. Experimental results showed that this technique could be
safely employed to study the dependence of refractive index of solutions on their
concentration as well as on the temperature. The temperature coefficient of refractive
index of water (in the range of 30-70°C) was determined and it was found that the value
is in agreement with the results obtained from other methods of measurement. A linear
dependence of refractive index of some solutions (common salt, sugar, propanol_1,
sucrose, potassium chloride) with their concentration was observed.
6
KATHMANDU UNIVERSITY JOURNAL OF SCIENCE, ENGINEERING AND TECHNOLOGY
VOL.II, No.1, FEBRUARYR, 2006.
ACKNOWLEDGEMENT
This work was supported by University Grant Commission (UGC) of Nepal under the
mini research project grant.
REFERENCES
1. Schwartz, A.M., Berglund, K.A., 1999. The use of Raman spectroscopy for in situ
monitoring of lysozyme concentration during crystallization in a hanging drop. J.
Crystal Growth, 203, 599.
2. Olesberg, J.T, Arnold, M.A, Hu, S-Y.B., Wiencek, J.M., 2000. Temperature
insensitive near infrared method for determination of protein concentration during
protein crystal growth. Analytical Chemistry, 72, 4985.
3. Shlichta, P. J., 1986. Feasibility of mapping solution properties during the growth
of protein crystals. J. Crystal Growth, 76, 656.
4. Miller, A., Hussmann, E. K., McLaughlin, W. L., 1975. Interferometer for
measuring fast changes of refractive index and temperature in transparent liquids
Review of Scientific instruments, 46, 1635.
5. McPherson, A., Malkin, A. J., Kuznetsov, Y. G., Koszelak, S., Wells, M., Jenkins,
G., Howard, J., Lawson, G., 1999. Effects of microgravity on protein
crystallization: evidence for concentration gradients around growing crystals , J.
Crystal Growth, 196, 572.
6. Garcia-Ruiz, J. M., Novella, M. L., Otalora, F., 1999. Supersaturation patterns in
counter-diffusion crystallisation methods followed by Mach-Zehnder
interferometry, Crystal Growth, 196, 703-710.
7. Otalora F, Novella ML, Rondon D, Garcia-Ruiz JM, 1999. Growth of lysozyme
crystals under micro gravity conditions in the LMS (STS-78) mission Journal of
Crystal Growth, 196, 649.
8. Miyashita, S., Komatsu, H., Suzuki, Y., Nakada, T., 1994. Observation of the
concentration distribution around a growing lysozyme crystal, J. Crystal Growth,
141, 419.
9. Lukin, O.V., Magunov, A. N., 1993. Temperature measurement of glass and
quartz plates by laser interferometry, Opt. Spectrosc., 74, 630.
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We present experimental observation of the spatio-temporal pattern of supersaturation in counter-diffusion methods. These complex patterns were recorded by dynamical interferometric analysis using a Mach–Zehnder configuration. Tetragonal hen egg white lysozyme crystals were grown inside APCF (advanced protein crystallisation facility) reactors. Salt and protein diffusion profiles were obtained independently by performing duplicated experiments with and without protein in the protein chamber; salt gradients were observed directly while protein concentration profiles are computed from the differences in refractive index between the two experiments. As expected from computer simulations, the time evolution of supersaturation shows a maximum about 45 h after activation (although this value can change as a function of the starting conditions and the geometry of the reactor). Nucleation takes place before this maximum supersaturation is reached. This explains the trend of the growth rate versus time curves for experiments performed within APCF reactors (both on ground and in space) and in capillaries by the gel acupuncture technique. By using very low concentration agarose gel in the protein chamber, sedimentation and buoyancy effects are eliminated so that the effects of gravity on fluid dynamics and hence on the spatio-temporal evolution of supersaturation can be assessed. These results confirm experimentally the predicted behaviour of counter-diffusion systems and support their use in growing large high-quality protein single crystals.
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Use of Raman spectroscopy for in situ monitoring of lysozyme concentration during crystallization in a hanging drop
Article
Fiber optic Raman spectroscopy combined with a partial least-squares regression model was investigated as a means to monitor lysozyme concentration during crystallization in a hanging drop experiment in real time. Raman spectral features of the buffer and protein were employed to build the regression model. This model was used to calculate the compositional changes within the hanging drop. The use of fibre optic technology coupled with Raman spectroscopy, which is ideal for use with aqueous media, results in a powerful noninvasive probe of the changing environment within the solution. These preliminary findings indicate that solubility as well as supersaturation measurements can be made.
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Temperature-Insensitive Near-Infrared Method for Determination of Protein Concentration during Protein Crystal Growth
Article
  • Nov 2000
A temperature-insensitive method for measuring protein concentration in aqueous solutions using near-infrared spectroscopy is described. The method, which is based on identification of the net analyte signal of single-beam spectra, can be calibrated using a single protein absorbance measurement and is thus well suited for crystallization monitoring where the quantity of protein is limited. The method is applied to measurements of glucose-isomerase concentration in a sodium phosphate buffer that is actively varied over the temperature range of 4-24 degrees C. The standard error of prediction using the optimized spectral range of 4670-4595 cm(-1) is 0.12 mg/mL with no systematic trend in the residuals with solution temperature. The method is also applied to previously collected spectra of hen egg-white lysozyme and yields a standard error of prediction of 0.14 mg/mL. Spectra sampled at discrete wavelengths can also be used for calibration and prediction with performance comparable to that obtained with spectral bands. A set of four wavelengths are identified that can be used to predict concentrations of both proteins with a standard error less than 0.14 mg/mL.
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Growth of lysozyme crystals under micro gravity conditions in the LMS (STS-78) mission
  • 649
  • Novella F Ml Otalora
  • Rondon D Garcia-Ruiz
  • Jm
Otalora F, Novella ML, Rondon D, Garcia-Ruiz JM, 1999. Growth of lysozyme crystals under micro gravity conditions in the LMS (STS-78) mission Journal of Crystal Growth, 196, 649.