High-temperature vacuum drying

A well defined amount of water, depending on the cation, is kept after vacuum drying (10 5 torr) at room temperature (fig. 1). This residual water (1 to 2 H2O/SO3 ) is desorbed after heating above the glass transition of the Nafion matrix. During rehydration of the high temperature vacuum dried sample the initial isotherm sorption curve is reobtained only above a well defined relative water pressure (fig. 2). 

Anhydrous a-dextrose is manufactured by dissolving dextrose monohydrate in water and crysta11i2ing at 60—65°C in a vacuum pan. Evaporative crysta11i2ation is necessary to avoid color formation at high temperatures and hydrate formation at low temperatures. The product is separated by centrifugation, washed, dried to a moisture level of ca 0.1%, and marketed as a very pure grade of sugar for special appHcations. 

The dioxane content is variable. Generally the amount of dioxane will fall in the range of 2.5 to 3.0 mols per mol of NaBuHu, provided that the sample is vacuum-dried for 24 hours at room temperature. Low carbon and high boron values will be obtained if the sample is not adequately protected from moisture. 

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