Standard for quantitative determn. of water consists of a solid porous substrate (I), prepd. with a solid chemical cpd. (II), which contains a reversibly combined stoichiometric amt. of water. (II) is pref. a cpd. contg. water of crystallisation; and (I) consists of ceramic material, which should be pure or chemically uniform, or absorbent paper. The standard is produced by preparing a soln. of a definite amt. of (II), taking an exact portion of the soln., impregnating (I) with this portion and removing the solvent and drying (I) with (II), which is now solid, at a suitable temp. Before use, the impregnated and dried (I) is stored in an air- and water-tight package, pref. welded in plastics film. USE/ADVANTAGE - The standard is esp. suitable for the determn. of water in high vacuum and at high temps., e.g. in semiconductor prodn. It can be made readily available and is reliable. It can be stored under any conditions when in a sealed package and is ready for use at any time. Troublesome weighing operations are eliminated and (I) is easier to handle than powders.
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