Ultrasonic Interferometer For Liquids

An ultrasonic interferometer is a simple and direct device to determine the ultrasonic velocity in liquids with a high degree of accuracy.
Using this instrument several Ph.D. Thesis are awarded and innumerable Research papers are published in National & International Journals . Velocity measurement combining with other physical quantities provides information of more than 30 Parameters . For ready reference few Equations are listed here . Few Experiments are also suggested for laboratory purpose .

The Ultrasonic Interferometer consists of the following parts :

- The High Frequency Generator
- The Measuring Cell
Optional Accessory : Constant Temperature Waterbath

The principle used in the measurement of velocity (v) is based on the accurate determination of the wavelength in the medium.

Ultrasonic waves of known frequency (f) are produced by a quartz crystal fixed at the bottom of the Ultrasonic cell. These waves are reflected by a movable metallic plate kept parallel to the quartz crystal and standing waves are formed in the medium. This acoustic resonance gives rise to an electrical reaction on the generator driving the quartz crystal.

If the distance between crystal and plate is now increased or decreased and the variation is exactly one half wavelength or multiple of it, anode current becomes maximum or minimum. From the knowledge of wavelength the velocity (v) can be obtained by the relation:
Velocity = Wavelength x Frequency


If the variation in the velocity with temperature is to be studied, water at various desired constant temperatures is made to circulate through the double walled jacket of the cell

A number of parameters related to ultrasonic velocity are:

· Compressibility
· Effective Debye Temperature
· Excess Enthalpy
· Hydrogen Bonding
· Intermolecular Free Length
· Solvation Number/ Hydration Number
· Vander Wall's Constant
· Rao's Constant
· Wada Constant
· Molecular Interaction
· Proton Relaxation Rate
· Relative Association
· Relaxation Time and Relaxation Strength
· Acoustic Impedence
· Stacking Constant
· Space Filling Factor
· Cohesive Energy Barrier
· Latent Heat Of Vaporisation
· Specific Heat Ratio
· Miscibility and Compatibility of Blends
  and many more