T IIE physico-chemical and phase behavior of sodium soaps in organic solvents has been investigated to some extent (7-10), and several physical properties of soap gels in pinene have also been reported (2-6). The systems of alkali soaps in toluene and Nujol are reported to gelate faster than those in xylene and pinene (1). An attempt is made in the present investigation to determine the effect of soap and solvent molecules on some physical-chemical properties of the resulting gels.
Materials Used and Experimental TechniqueThe sodium palmitate and sodium oleate were products of the British Drug Houses and had melting points of 270~ and 232~ respectively. The sodium stearate was a pure product of E. Merck and had a melting point of 260~ n-Amyl, butyl (n-and iso-), and propyl (n-and iso-) alcohols, and anisole were products of E. D. Haen; toluene, xylene, chlorobenzene, bromobenzene, o-cresol, and glycerol of the British Drug ]Iouses; phenol and p-chlorotoluene of E. Merck; benzyl alcohol of van Ameringen Ilaebler Inc., cymene of Dr. T. Schuchardt's laboratories; and pinene of E. Kodak and Company. All these solvents were used without further purification other than drying and storing over anhydrous calcium sulfate.Gel-forming solutions were prepared in Pyrex glass tubes (2r = 1.45 cm.) by dissolving a known amount of a soap in 10 ml. of an organic solvent at a temperature nearabout the boiling point of the latter. An air condenser was attached to prevent evaporation of the solvent, and the system was stirred constantly. When the soap had dissolved completely, the test tubes were placed in a thermostat maintained at 30~The procedural details employed in measuring the setting time (6), syneresis (5), and gel-strength (4), were the same as those used in earlier investigations. The setting time was measured at 30~ by determining the time which the gel-forming system took to reach a consistency when it did not flow out of the container when it was inverted. The extent of syneresis was determined two hours after the systems had set to the gel state at 30~The test tubes were weighed before and after the removal of the syncretic liquid with small rolls of filter paper, and the difference in weights was taken as a measure of the exuded synereticum. In making gel-strength measurements, small weighing bottles (2r ~-2.4 cm.) and a fiat disc-shaped plunger (2r = 0.8 era.) were used. The plunger was attached to the bottom of the pan of a balance and was placed gently in contact with the top of the gel; weights were slowly added to the pan and the corresponding deflections on the scale as indicated by the I)ointer were noted. The load necessary to produce a shift of 10 scale divisions was determined in each ease. The, temperature, time interval, and other factors were chosen arbitrarily since the main purpose of this investigation is to determine the nature of changes brought about in the physical properties of gels with changes in soap and solvent types rather than-to obtain "absolute" values for the same.The various results of ...
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