These chemistry students were doing a lab called Stoichiometry and Gravimetric Analysis.  The procedure they used is similar to one that could be used commercially to determine how much of a particular compound is present in a large amount of solution.

The students combined aqueous sodium carbonate with aqueous calcium chloride.  This reaction produces sodium chloride in solution and a precipitate of calcium carbonate.  The students collected the calcium carbonate using a simple filter apparatus of a funnel with filter paper and an Erlenmeyer flask.   They allowed it to dry and later measured its mass, and they had measured the amounts of the solutions they combined.  The students will use this information to determine how many moles and grams of the reactants and products were present in this reaction, and they will use conversions to ultimately determine what mass of dissolved calcium carbonate would be present in a much larger sample size.