Nomograph for Paraffin Wax Solubility in Petroleum Fractions J
D. S . DAVIS, Wayne University, Detroit, Mich. ERNE-Allen and Work' presented excellent data on the solubility of commercially refined paraffin waxes in petroleum distillates. The data take the form of straight-line isotherms when the logarithm of the wax solubility is plotted against the solution equilibrium temperature; and quantitative relations between solubilities, paraffin wax melting point, the average boiling point of the solvent, and the solution equilibrium temperature were established. The authors gave their data a m a t h e m a t i c a l treatment adequate from theoretical and empirical standpoints and arrived at the following expression:
B
X where X
= (1120 - 2,97Y)1.1357'-m = solubility, grams wax/100
ml. solveni' Y = av. solvent boiling point, " C. (based on temD. at 10, 30, 50, 70, and 90 6er cent points, A. S. T. M. distillatpn) m = melting point of wax, C. t = solution equilibrium temp., " C.
Berne-Allen and Work also included a Tectilinear chart for solution of their equation; the variables are plotted in such a manner that a double pencil of intersecting lines results. While obviating considerable slide-rule manipulation, the chart is somewhat difficult to read for high values of the melting point and solution temperature, and interpolation is not convenient. I n view of the evident value of the data and their industrial application, it appears worth while to offer a nomograph for the solution of the equation. The accompanying alignment chart is extremely "open" and permits of easy interpolation along closely graduated scales. The use of the chart may be illustrated as follows: What is the solubility of paraffin wax in petroleum when the melting point of the wax is 45"C.,the temperature of the solution is 26" C., and the average boiling point of the pure distillate is 260" C.? The difference between the melting point and the solution temperature is 45 - 26 or 19" C. Connect 19 on the right-hand scale with 260 on the left-hand scale, and read the solubility on the inclined axis as 31.0 grams of wax per 100 ml. of solvent. Similarly the chart reveals that 100 ml. of a distillate boiling a t 190" C. will dissolve 5 grams of paraffin wax when the melting point of the wax is 60" C. and the temperature of the solution is 23" C. Note that one reads solubilities on the right-hand side of the inclined scale
' I N D . ENG C H E h l , 30, SO6
(1935).
when temperature differences are read on the right-hand side of the temperature difference scale, and conversely. The same equation could have been handled by the more familiar parallel-scale logarithmic chart, bearing singly graduated axes, with less labor in construction but at the sacrifice of some precision. Area for area, the present 2-type nomograph is more advantageous to the user.
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