03_Gravimetry-page9 - The best way to deal with these...

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Unformatted text preview: The best way to deal with these problems is to slow things down. Using dilute, warm solutions during precipitation gives counter ions time to leave and helps break up pockets. Digestion and aging the precipitate provides additional times for this to occur as well. When a precipitation reagent is added as a solution to our analyte there will always be locally high concentrations. This is responsible for many of our problems regardless of how slowly we add the reagent or how fast we stir. Precipitation from homogeneous solution is an an approach that can avoid this problem. After filtration, the precipitate must be dried to constant weight. Removes excess solvent Drives off any volatile species. In some cases, the precipitate is heated to a point where it decomposes to a stable form for weighing. Thermobalances can be used to determine optimum drying time and temperatures. ...
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This note was uploaded on 01/07/2012 for the course CHEM 290 taught by Professor Harvey during the Fall '08 term at SUNY Stony Brook.

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