How to Separate BaCl2 From CaSO4

Fill one beaker no more than two-thirds full with water. The amount of water you use will depend on what quantity of mixture you want to separate. About 36 g of barium chloride will dissolve in 100 mL of room temperature water, so if your mixture is half and half, you should use at least 100 mL of water for every 72 g of mixture.

Weigh out the amount of mixture that you wish to separate. You will want to weigh out no more than 72 g for every 100 mL of water, assuming the mixture of the two is equal.

Pour the weighed out portion of the mixture into the beaker of water and stir for at least 5 minutes. The BaCl2 will dissolve but the vast majority of the CaSO4 will not, since the solubility of this chemical at room temperature water is only 0.2 g per 100 mL; less than one hundred times the solubility of BaCl2.

Place the funnel in an empty beaker and place a conical filter paper in the funnel. You can pre-wet the paper with some water to enable it to better stick to the inner walls of the funnel.

Pour the solution of your mixture in water into the funnel, ensuring that none of it flows between the filter paper and the inner walls of the funnel. The undissolved calcium sulfate will be caught on the filter paper and the water containing the dissolved barium chloride -- with a small trace of calcium sulfate -- will pass through the paper into the collection beaker.

Set the filter paper and solid calcium sulfate aside to dry. You have now separated the mixture. If you like, you can heat the filtered solution to evaporate the water and recover the dissolved barium sulfate.