Date on Master's Thesis/Doctoral Dissertation

1947

Document Type

Master's Thesis

Degree Name

M. Eng.

Department

Chemical Engineering

Committee Chair

Ernst, Robert Craig

Committee Co-Chair (if applicable)

Williams, Gordon C.

Committee Member

Stevenson, Guy

Subject

Coacervation

Abstract

An analysis of the literature shows the close analogy between liquid crystalline phases in solution (fluids separating from main portion of solution and having some of the directional properties of crystals) and unipolar coacervates (solvated micelles of like charge separating as a distinct colloidal phase). A theory is here advanced that liquid crystalline phases in solution are the direct result of a maximum in osmotic pressure which is predictable from the first approximate equation of the Debye-Huckel theory in the same manner as unipolar coacervates were predicted by I. Langmuir. Application of the theory to aqueous soaps, investigated by Vold and associates, and to aqueous 10-bromo and 10-chlorophenanthrene-6-sulphonic acid has shown remarkably good agreement. As a further step toward testing the theory a study has been made of the osmotic behavior of aqueous Amaranth and Napthol Yellow S solutions at 20*C, utilizing the indirect method of calculation based on measurement of the concentrations of isopiestic solutions. The supposition that these dyes have liquid crystalline phases in aqueous solution has been confirmed by plots of molar concentration versus osmotic pressure which show discontinuities (constant osmotic pressure over a range of concentration) indicating two liquid phases in equilibrium namely, the liquid crystalline phase and isotropic solution. In the case of Napthol Yellow S two discontinuities have been developed below the normal limit of solubility given by Holmes whereas Amaranth has only one. Thus a narrower concentration range for the liquid crystalline phase is indicated for the yellow. These facts have been interpreted utilizing proposed equilibrium diagrams. Application of the theory to the first (lowest concentration) discontinuity has shown good agreement for Amaranth and less satisfactory agreement for Napthol Yellow S. In the latter case differences between fact and theory have been reconciled based on differences in molecular structure. Predicting higher order transitions is not considered to be within the scope of the present theory because fundamentally the Debye-Huckel first approximate equation is a dilute solution theory. Moreover, the equation would be expected to show agreement only when the mass is isotropic regardless of concentration. The fact that the equation takes no account of molecular constitution other than state of charge (ionic valence) is emphasized. It has been concluded that the present theory is highly satisfactory provided it is not applied indiscriminately.

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