Date of Award

6-1960

Document Type

Open Access

Degree Name

Bachelor of Science

Department

Chemistry

Language

English

Abstract

When solutions of zirconium oxychloride and sodium acetate are mixed at room temperature (25°c.), a grey-white hydrogel of zirconia is formed. This gel structure gradually weakens on standing, and finally becomes a water-clear sol. Heating this sol to 6o°c. will form a similar gel, stable at this temperature, which will reliquefy on cooling to 25°c. The gelation-reliquefaction cycle can apparently be carried out indefinitely. Such behavior is in direct contrast to normal gelation. The so-called “irreversible gels”, such as those of silicic acid, show stability at all temperatures; while other “reversible gels”, such as common gelatin, set at lower temperatures and become liquid on heating. McBain (1) mentions certain organic gels, such as those of methyl cellulose in water and cellulose nitrate in alcohol, which set on heating and liquefy on cooling. Such gels do not, however, first set and then reliquefy at room temperature. There have been several previous studies seeking to determine the various ionic changes and interactions that govern this unique behavior. Unfortunately, these theories have not been substantiated by experimental findings. The present study is primarily concerned with a qualitative explanation of the phenomenon; i.e., the basis for gelation and reliquefaction in broad terms. When this has been accomplished, it would then seem proper to construe a reaction mechanism.

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In Copyright - Educational Use Permitted.