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Gravimetric Analysis

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danielf:
New to the site and hopin someone could lend a hand for my first SAC. Part 1 is a gravimetric analysis, one of the questions is 'why does the crucible have to be cool when weighed?' I've been told it has something to to with water adsorption to the porcelain however some more definite explanations would be greatly appreciated.
Thanks heaps

Four:
My gut feeling here is that a hot crucible would damage the scales; electronic scales are very sensitive, and putting a hot crucible on it would be a no-no. The crucible is heated to remove any water content in the salt, sure, but keeping the water out would require a desiccator rather than a cool crucible.

iamdan08:
The crucible has to be cooled to room temperature because if it was still hot, the higher temperature would cause air currents around the balance, giving inaccurate results.

danielf:
Good point, thanks

purple_rose:
Wot questions would u expect to be on a PRAC SAC  involving, finding the sulfate content in fertiliser by the means of gravimetric analysis (I don't mean conclusion, obervation, aim...etc)?

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