Gravimetric Analysis of Phase Systems using a Microwave Oven and the Rapid Determination of Phase Diagrams
The first step in the preparation of a phase diagram is the determination of the polymer content of the phases. In the method described here, the dextran content of a dextran:PEG phase system is determined using a polarimeter with a cell with a 5.025 cm path length. Under these conditions the rotation recorded has the same value as the dextran concentration in grams per decilitre. The cell is also designed to be used with viscous solutions so that stock solutions of dextran (at 20%) can be standardised directly, avoiding dilution errors and the sometimes inadvertent confounding of w/w and w/v measures. The w/v value is converted to w/w using the formula of Brooks et al . At this point it should perhaps be noted that when using a polarimeter to determine the dextran content of a phase from a two-phase system, the temperature of the polarimeter cell must not be lower than that at which the phases were equilibrated. At lower temperatures the phases will become turbid as a new equilibrium is established.
KeywordsPhase Diagram Gravimetric Analysis Microwave Oven Absorptive Capacity Phase System
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