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The viscosity of fluids in the critical region


Strumpf, Hal Jeffry (1972) The viscosity of fluids in the critical region. Dissertation (Ph.D.), California Institute of Technology.


The viscosity of xenon has been measured along ten isochores and the viscosity of ethane has been measured along five isochores in the region of the gas-liquid critical point. The viscometer was a specially cut quartz cylinder, which was excited into a torsionally oscillating mode upon application of an alternating voltage. The cylinder, oscillating in this manner, generated a viscous wave when immersed in a fluid. The viscous wave caused an impedance loading on the quartz which changed its resonant resistance and frequency. This change in resonant properties can be related to the viscosity-density product of the fluid.

The resonant properties of the quartz crystal were measured by connecting the crystal to the unknown arm of a Wheatstone bridge circuit, modified so as to measure parallel resistance and capacitance. The crystal was driven by a very stable frequency generator, and the circuit was tuned using an oscilloscope as a null detector.

The crystal was enclosed in a high pressure stainless steel cell and placed in a water thermostat which controlled temperature to ± 0.001°C. The temperature was measured with a calibrated platinum resistance thermometer. The density was determined by a gravimetric technique.

The viscosities exhibit an "anomalous" increase as the critical temperature is approached along an isochore of close to critical density. The anomaly is consistent with a logarithmic divergence of the form:

∆ƞ = A log ɛ + ʙ

where ∆ƞ is the anomalous viscosity, ɛ is the reduced temperature difference from critical, and A and ʙ are constants. The possibility of an exponential divergence or a cusp-type finite limit for viscosity is not precluded, however.

The critical temperatures and densities have been determined by visual observations. For xenon, Tc = 16.627 ± 0.005°C, ρc = 1.11 ± 0.01 g/cm3 ; for ethane, Tc = 32.218 ± 0.005°C, ρc = 0.2055 ± 0.002 g/cm3. The temperatures are stated with respect to the 1968 International Practical Temperature Scale.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemical Engineering
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Pings, Cornelius J.
Thesis Committee:
  • Unknown, Unknown
Defense Date:21 April 1972
Funding AgencyGrant Number
Stauffer FellowshipUNSPECIFIED
New York State Regents FellowshipUNSPECIFIED
Fluor FellowshipUNSPECIFIED
Record Number:CaltechTHESIS:09062016-112046701
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9913
Deposited By: Leslie Granillo
Deposited On:07 Sep 2016 19:31
Last Modified:07 Sep 2016 19:31

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