Document Type


Date of Award

Spring 5-31-1960

Degree Name

Master of Science in Chemical Engineering - (M.S.)


Chemical Engineering

First Advisor

Saul I. Kreps

Second Advisor

C. L. Mantell

Third Advisor

George C. Keeffe


The absolute viscosity of the normal paraffins C5H12 to C20H42 was studied to determine a relationship more useful in predicting liquid viscosities than existing correlations such as the methods of Andrade, Souders, Thomas, and Doolittle.

It was found that a function of corresponding liquid states could be designed which related viscosity to the number of carbon atoms. This function, here called liquidity, is defined as the extent to which a substance exists as a liquid with respect to temperature. This function can be expressed mathematically as:

Lc = (t - tm)/(tc - tm) or Lb = (t-tm)/(tb-tm);

Lc = liquidity based on the critical temperature
Lb = liquidit based on the normal boiling temperature
t = any temperature, °C
tb = normal boiling temperature, °C
tc = critical temperature, °C
tm = normal melting temperature, °C

Once the basis for liquidity is determined, the denominator in the above expressions remain constant, and the % liquidity becomes a straight line function of the temperature.

It was further found that a plot of Lc vs. number of carbon atoms for the n - paraffins resulted in curves of iso - viscosity which, when fitted to straight lines, could be used for calculation, extrapolation, or interpolation of viscosity data. Thus, a method was developed for the viscosity prediction of the n - paraffins above C4H10 to apply at any temperature within the normal liquid range. Deviations from the experimental values of viscosity to those resulting from the designed liquidity function are within ± 10 per cent for the majority, and less than ± 20 per cent for the extreme cases. This approach to viscosity prediction is valid with or without the availability of experimental data.



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