IMPURITY CONCENTRATION PROFILES IN ICE BY AN ANTHRONE METHOD

Abstract

Solutions of sodium carboxymethyl cellulose (CMC), sodium chloride, ethylene glycol, and ethyl alcohol in water were prepared and frozen under controlled conditions. The ice in each case was divided into horizontal sections, melted, and the amount of each impurity measured. The organic liquid and salt concentrations were found from refractive index values using a dipping refractometer, and the CMC content, after treatment with an anthrone solution, was measured with a spectrophotometer. Developments in the anthrone method are described. Qualitative tests were also made by freezing solutions of soluble dyes.In the freezing of aqueous solutions of CMC and the dyes, rejection of the impurity is almost complete. When solutions of salt or alcohol or glycol in water, or of CMC and alcohol or glycol in water, are frozen a surface concentration peak and a second peak about 7 mm below the surface, corresponding to a previously observed discontinuity in the crystal structure of impure ice, are found. The ability of alcohol or glycol to carry CMC or a dye to places in the ice structure not available to them in the absence of the organic liquid is noted.