Question

After removing a crucible (containing CaCO3 obtained as a precipitate) from an oven, what could you do (if you were being extremely careful and had enough time) to prove that the CaCO3 is dry?

Answer 1

Let the crucible and contents cool in a desiccator. Weigh accurately. Reheat the crucible and contents for an hour, cool, and reweigh. I like to see the same mass both times, at least to within 0.2 mg if this is being done on an analytical balance and it is standard quant and not semi-micro or micro quant.