International Journal of Science and Engineering Applications
Special Issue NWLM ISSN-2319-7560 (Online)
Ultrasonic Studies on Molecular Interactions of
Potassium Bromide in Aqueous Lactose Solution at
Varying Molalities and Temperatures
V. Rohini
Department of Physics
KGiSL Institute of Technology
Coimbatore, Tamil Nadu
India
R. Kesavasamy
Department of Physics
Sri Ramakrishna Engineering
College
Coimbatore, Tamil Nadu
India
N.S. Priya
Department of Physics
Sri Ramakrishna Engineering
College
Coimbatore, Tamil Nadu
India
Abstract: The present experimental investigation was carried out in order to explore the possible molecular interactions of
potassium bromide in aqueous lactose solution at 303, 308, 313 K. Experimental values of density (ρ), viscosity (η) and ultrasonic
velocities (U) were carried out on the liquid ternary mixtures of water + lactose + potassium bromide. The binary solvent mixture
of water + lactose (15%) was prepared under molality (m) basis. Potassium bromide was added under different molalities with
these binary solvent mixtures. The related parameters correlated to our present study such as adiabatic compressibility, change and
relative change in adiabatic compressibility, acoustic impedance, intermolecular free length, classical absorption coefficient,
relative association, relaxation time were determined. The present investigation deals with the possible molecular interactions such
as ion-ion, ion-solvent, solute-solvent, solute-solute which are identified and eventually discussed about the behavior of solute
(potassium bromide) in the solvent mixture.
Keywords: Ultrasonic velocity, potassium bromide, adiabatic compressibility, free length, relaxation time.
1. INRODUCTION
Studies on interactions of non ionic solutes with ionic ones in different solvents are significant for investigating their physicochemical behavior. The study of carbohydrates and saccharides has become a subject of increasing interest because of the
multidimensional, physical, biomedical, and industrially useful properties of these compounds. So, studies on the thermodynamic
properties of biological molecules in aqueous solutions are important. Studies involving density and ultrasonic velocity
measurements are important for elucidation of ion-solvent, ion-ion and solute-solvent interactions in the mixed solvent systems.
Interactions of electrolytes with saccharides are very important in exploring the stability of polysaccharides in biological systems
as well as in the chemical industry of saccharides.
The present study investigates the behavior of potassium bromide in aqueous lactose of 15% by using acoustic measurements. In
this paper, we report the densities and ultrasonic studies at different temperatures (i.e., 303K, 308K, and 313K) over a wide
concentration range. These data were used to calculate various acoustic parameters like adiabatic compressibility, change and
relative change in adiabatic compressibility, acoustic impedance, intermolecular free length, relative association, relaxation time,
classical absorption coefficient. These parameters are discussed in terms of various solute-co solute interactions in aqueous
solutions; thus the study contributes to a better understanding of the interactions taking place between solute and solvent.
2. MATERIALS AND METHODS
All the chemicals used in this present research work are spectroscopic reagent (SR) and analytical reagent (AR) grades of minimum
assay of 99.9%. Water used in these experiments was deionized, distilled and degassed prior to prepare solutions. Required amount
of water and lactose were taken to prepare the composition of binary mixtures in a dry clean conical flask with a ground stopper.
The required quantity of electrolytes for given molality was dissolved in binary mixture of aqueous lactose of 15%. Similar
procedure has been adopted for different molarities of electrolytes. For each concentration, the mass of potassium bromide can be
measured using electronic digital balance have an accuracy of ± 0.1 mg. The density was using a specific gravity bottle by relative
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International Journal of Science and Engineering Applications
Special Issue NWLM ISSN-2319-7560 (Online)
measurement method with an accuracy of ±0.1 Kgm-3. An Ostwald’s viscometer (10ml capacity) was used for the viscosity
measurement. An ultrasonic interferometer having the frequency 2 MHz (Mittal enterprises, New Delhi, Model: F81) with an
overall accuracy of ±0.1% has been used for velocity measurement. An electronically digital operated constant temperature bath
has been used to circulate water through the double walled measuring cell made up of steel containing the experimental solution at
the desired temperature.
3. THEORY AND CALCULATIONS
Using the measured data, some acoustical parameters such as adiabatic compressibility (β), change (∆β) and relative change in
adiabatic compressibility (∆β/ β0), acoustic impedance (Z), intermolecular free length (Lf), relative association (R.A.), relaxation
time (τ), classical absorption coefficient (α/f2 ) were studied and evaluated by using the standard equations:
Adiabatic compressibility (β) =
1
𝜌𝑈 2
(1)
Where U is the ultrasonic velocity and ρ is the density
Change in adiabatic compressibility (∆β) = (β- β0)
(2)
Where β and β0 are the adiabatic compressibility of solution and solvent respectively.
Relative change in adiabatic compressibility = (∆β/ β0)
(3)
Acoustic impedance (Z) = Uρ
(4)
Intermolecular free length (Lf) = 𝐾β12
(5)
1
Relative association (R.A) =
Relaxation time (τ) =
𝜌 𝑈0 3
.
𝜌0 𝑈
4𝜂
3𝜌𝑈 2
(6)
(7)
4. RESULTS AND DISCUSSION:
The experimental values of density, ultrasonic velocity, adiabatic compressibility, change and relative change in adiabatic
compressibility for different molal compositions of potassium bromide in 15 wt. % lactose at different temperatures (i.e., 303K,
308K, and 313K) are shown in Table-1.
The results show that the densities and ultrasonic velocities increases with increase in the concentration of lactose as well as with
the concentration of potassium bromide. Moreover, the density decreases with increasing temperature in all the systems while the
opposite trends are observed for ultrasonic velocity. The increased of ultrasonic velocity with temperature in all systems indicates
a weakening of solute-solvent interactions at higher temperatures. As the temperature increases, hydrogen bonds between water
and lactose molecules break. The decrease in adiabatic compressibility observed in the present system due to increase in
electrostriction compression of solvent around molecules which results in a large decrease in the compressibility of solutions. The
negative values of change in age in adiabatic compressibility and relative change in adiabatic compressibility are due to solutesolvent interactions. Such an increase in values with increase in concentration may be attributed to an overall increase in the
cohesive forces in the solution. These cohesive forces may be due to the interactions in the solution.
It is clear from table that ultrasonic velocity increases and intermolecular free length decreases with increase in concentration of
potassium bromide in 15 wt. % lactose at different temperatures (i.e., 303K, 308K, and 313K). The decrease in the value of free
length with increase in molality indicates the presence of significant ion-solvent interaction between solute and solvent molecules
due to which the structural arrangement in the neighborhood of constituent ions is considerably affected. The sample plots of
adiabatic compressibility, free length, relaxation time, acoustic impedance with molality for KBr in 15% lactose at different
temperatures is shown in figures.
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International Journal of Science and Engineering Applications
Special Issue NWLM ISSN-2319-7560 (Online)
Table-1: Density (ρ), ultrasonic velocity (U), adiabatic compressibility (β), change (∆β) and relative change in adiabatic
compressibility (∆β/ β0) for potassium bromide in 15 wt. % lactose at different temperatures (i.e., 303K, 308K, 313K)
Molality
Ρ x 103
U
(m)
(Kgm-3)
(ms-1)
Potassium bromide in 15 % aqueous lactose
Temperature = 303K
0.00
1.053
1539.2
0.02
1.052
1544
0.04
1.053
1550.8
0.06
1.056
1551.2
0.08
1.057
1553.6
0.1
1.058
1565.2
Temperature = 308K
0.00
1.050
1542.4
0.02
1.052
1549.6
0.04
1.053
1554.8
0.06
1.0556
1556.4
0.08
1.057
1558.4
0.1
1.058
1566.8
Temperature = 313K
0.00
1.049
1552.2
0.02
1.051
1556.4
0.04
1.052
1558.4
0.06
1.0549
1562.8
0.08
1.0558
1566.4
0.1
1.0574
1569.2
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β x 10-10
(Pa-1)
-∆β x10-10
(Pa-1)
-∆β/ β0 x 10-3
4.0084
3.9760
3.9375
3.9280
3.9122
3.8508
0.0324
0.0709
0.0804
0.0962
0.1576
8.0830
17.6878
20.0578
23.9996
39.3174
4.0032
3.9586
3.9284
3.9107
3.8955
3.8502
0.0446
0.0748
0.0925
0.1077
0.1530
11.1410
18.6850
23.1065
26.9034
38.2194
3.9566
3.9278
3.9140
3.8813
3.8602
3.8406
0.0288
0.0426
0.0753
0.0964
0.1160
7.2789
10.7668
19.0314
24.3643
29.3181
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International Journal of Science and Engineering Applications
Special Issue NWLM ISSN-2319-7560 (Online)
Table-2: Acoustic impedance(Z), intermolecular free length (Lf), relative association (R.A.), relaxation time (τ), classical
absorption coefficient (α/f2) for potassium bromide in 15 wt. % lactose at different temperatures (i.e., 303K, 308K, 313K)
Molality
Z x 106
Lf x 10-10
-2 -1
(m)
(Kgm s )
(m)
Potassium bromide in 15 % aqueous lactose
Temperature = 303K
0.00
1.6207
0.3994
0.02
1.6289
0.3978
0.04
1.6376
0.3959
0.06
1.6411
0.3954
0.08
1.6452
0.3946
0.1
1.6591
0.3915
Temperature = 308K
0.00
1.6195
0.4024
0.02
1.6301
0.4001
0.04
1.6372
0.3986
0.06
1.6429
0.3977
0.08
1.6470
0.3969
0.1
1.6472
0.3946
Temperature = 313K
0.00
1.6282
0.4038
0.02
1.6357
0.4023
0.04
1.6394
0.4016
0.06
1.6485
0.3999
0.08
1.6538
0.3988
0.1
1.6592
0.3978
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R.A.
τ x10-12
(s)
α/f2 x 10-11
1.0008
1.0003
1.0021
1.0025
1.0010
2.3819
2.4091
2.4090
2.4204
2.4374
2.5475
4.7018
4.7476
4.7552
4.7779
4.8113
5.0287
1.0003
1.0001
1.0017
1.0032
1.0023
2.0895
2.1174
2.1280
2.1351
2.1642
2.1872
4.1246
4.1797
4.2007
4.2147
4.2720
4.3176
1.0010
1.0015
1.0024
1.0026
1.0039
1.9375
1.9427
1.9448
1.9726
2.0179
2.0590
3.8246
3.8349
3.8391
3.8938
3.9833
4.0644
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International Journal of Science and Engineering Applications
Special Issue NWLM ISSN-2319-7560 (Online)
Adiabatility Compressibility
4.05
4
3.95
303K
3.9
308K
313K
3.85
3.8
3.75
0
0.02
0.04
0.06
0.08
0.1
Molality
Fig. 1: Plots of β vs m for KBr in 15% lactose at different temperatures
1.67
Acoustic impedance
1.66
1.65
1.64
303K
1.63
308K
313K
1.62
1.61
1.6
1.59
0
0.02
0.04
0.06
0.08
0.1
Molality
Fig. 2: Plots of Z vs m for KBr in 15% lactose at different temperatures
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International Journal of Science and Engineering Applications
Special Issue NWLM ISSN-2319-7560 (Online)
0.406
0.404
0.402
0.4
Free length
0.398
0.396
303K
0.394
308K
0.392
313K
0.39
0.388
0.386
0.384
0
0.02
0.04
0.06
0.08
0.1
Molality
Fig. 3: Plots of LF vs m for KBr in 15% lactose at different temperatures
3
Relaxation time
2.5
2
303K
1.5
308K
313K
1
0.5
0
0
0.02
0.04
0.06
0.08
0.1
Molality
Fig. 4: Plots of τ vs m for KBr in 15% lactose at different temperatures
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International Journal of Science and Engineering Applications
Special Issue NWLM ISSN-2319-7560 (Online)
5. CONCLUSION
The Physico-chemical studies of solute-solute and solute-solvent interactions of potassium bromide in aqueous lactose at different
temperatures (i.e., 303K, 308K, and 313K) have been investigated. There exist molecular interactions in the systems. Both the
solute-solute interactions and solute-solvent interactions are possible in the systems. Due to increase in density and decrease in
intermolecular free length with increase in concentration indicating the loosening of intermolecular forces in aqueous lactose at
different temperatures (i.e., 303K, 308K, 313K). Hence it is evident that the ultrasonic velocity measurement in the given medium
serves as a powerful probe in characterizing the physic-chemical properties of that medium.
6. AKNOWLEDGEMENT
The author thanks Dr. R. Kesavasamy, Department of Physics for constant support and encouragement.
7. REFERENCES
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[3]Kannappan,AN & Palani, R 2007, Ultrasonic investigations in amino acids with aqueous dimethyl formamide,
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[4] S. Thirumaran and N. Prakash, Interactions of metal chlorides in aqueous sucrose solutions, J. Scientific
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[5] Shashi kant,Parul,Kamini Sharma, Interionic interactions of KBr in aqueous lactose solution, I. J. ChemTech
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[6] R. Palani and A. Geetha, Acoustical behavior of disaccharide in aqueous solutions of alkali metal halides, Rasayan
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