Thermal Properties of Some Organic Liquids Using Ultrasonic Velocity Measurements

Journal of Chemistry, May 2019

Debye temperature and thermal relaxation time has been calculated in normal and boiling temperature. Using thermal relaxation time, the heat of fusion has been calculated for nineteen organic liquids and the results throw light on the method of calculating heat of fusion.

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Thermal Properties of Some Organic Liquids Using Ultrasonic Velocity Measurements

E-Journal of Chemistry 0973-4945 Thermal Properties of Some Organic Liquids Using Ultrasonic Velocity Measurements P.RAMADOSS 0 1 2 N.BUVANESWARI 0 1 2 0 Department of Physics, Government Arts College Tiruvannamalai-606 603 , Tamilnadu , India 1 Keyword: Debye temperature, Heat of fusion , Ultrasonic velocity, Thermal properties 2 Suryanarayana C V , Indian J Chem., 1986, 25A, 538. Barnat S, J Chem Phys., 1952, 20, 278. Rama Rao, Curr Sci., 1954, 23, 325. Durai S and Ramadoss P, J Pure Appl Ultrason., 2006, 28, 1. Palani. R and Jaya chitra. K, Indian J Pure Appl Phys., 2008, 46, 251. Rajagopal K and Edwin Gladson S, J Pure Appl Ultrason., 2006, 28, 87. Ramadoss.P. Proceedings XVIII National Symposium on Ultrasonics, 21-23 Dec - 2009, 537. Kor.S.K and Tripathi N D, J Phys Soc Japan , 1967, 23, 476 Frenkel J , Kinetic Theory of Liquids, Oxford University Press Newyork , 1946. Kittel C, J Chem Phys., 1946, 14, 614. Tonks L, Phys Rev., 1936, 50, 955. Kaye G W C and Laby T H , Physical and Chemical Constants and Some Mathematical Functions , 13 Debye temperature and thermal relaxation time has been calculated in normal and boiling temperature. Using thermal relaxation time, the heat of fusion has been calculated for nineteen organic liquids and the results throw light on the method of calculating heat of fusion. Physical, chemical and thermo acoustical parameters of liquids, liquid mixtures, polar and non polar solutions and liquefied gases are very important for industrial applications. Ultrasonic velocity measurements has been carried out to bring out physical, chemical and thermal properties of liquids, liquid mixtures, polar and non polar solutions using its allied parameters like density, viscosity, surface tension etc., Ultrasonic measurement is one of the easiest method to calculate the properties of liquids like compressibility, internal pressure and so on1-7. Introduction Theory and calculations Ultrasonic velocity and applied parameters are used to calculate Debye temperature as8 ? = (h/kB) {[9N/4?V]/[(1/Cl3 )+(2/Ct3 )]}1/3 (1) Where, h is the Planck?s constant in Js, kB is the Boltzmann?s constant in J/K, N is the Avagadro number in kg/mol, 3 V is the volume of the liquid m . 1 ? 1 + ? ? 3 / 2 C 3 = ? ? 1 ? 3(1 - 2? )? 1 ? 2(2 +? ) ? 3/ 2 C 2 = ? ? 1 ? 3(1- 2? )? (?? )3/ 2 T (?? )3/ 2 T Cl is velocity of longitudinal waves in m/s, Ct is velocity of transverse waves in m/s, ? is the density of liquid in kg/m3 ?= (3A-2)/(6A+2) A=4/3 (1/?) ?T= ?s= 1/u2? ?T is adiabatic compressibility of liquid in m2/N ?s is the isothermal compressibility of liquid in m2/N ? is ratio of specific heats in m2/N Relaxation time is related with Debye temperature as9 ? = (h/2??DK?) Where, ?B is relaxation time at boiling temperature in sec ?R is relaxation time at normal temperature in sec Sound velocity at boiling temperature is calculated using the relation10-11 C gas = Cliqud (Vf/V)1/3 V is the molar volume of the liquids in m3 Vf is the free volume in m3 Results and Discussion In all system, densities and velocities at boiling temperature are less than the normal temperature. This is due to free space created between the molecules/atoms by temperature. This is conformed by the value of Debye temperature. The value of debye temperature at boiling point is less than those at normal temperature that is the disorder increases at boiling temperature. (2) (3) .(4) (5) (6) (7) (8) (9) Thermal Properties of Some Organic Liquids Calculated heat of fusion from Debye?s relaxation time throws light on the author?s idea. Literature value available is presented in parenthesis12. The deviation may be explained after elaborate study. Conclusions From this study, ultrasonic velocity at boiling temperature, values of thermal properties like Debye?s temperature and relaxation time at normal and boiling temperature are expected range, that is Debye temperature at normal temperature > boiling temperature and relaxation time at normal temperature < boiling temperature. Another thermal property, heat of fusion from thermal relaxation time is a fresh attempt for organic liquids. Values of heat of fusion support new approach. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 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P. Ramadoss, N. Buvaneswari. Thermal Properties of Some Organic Liquids Using Ultrasonic Velocity Measurements, Journal of Chemistry, DOI: 10.1155/2011/120260