Task: To make pure salt from impure salt.
Required accessories: The heterogeneous mixture of impure salt, stirrer, tripod stand, wire-net, funnel, filter paper, stand with ring, water.
Procedure: At first take a filter paper and fold it into four equal parts. Next set it in the funnel keeping three folds at one side and one fold at the other side as shown in the figure. Soak the filter paper slightly with water so that the filter papers do not get displaced. Place the funnel in the ring attached to the stand as shown in the figure. Keep a beaker under the funnel. Now, pour the heterogeneous mixture of impure salt (taking from the precious experiment) slowly on the filter paper. Wait until all the clean water drains out of the funnel.
Now dry up the entire water by placing beaker of pure saline water on the wire net over the tripod stand and applying heat at the bottom of the beaker with the help of burning spirit lamp.
What happened after pouring the mixture in the funnel? The impurity (soil particles) free pure saline water slowly passes through the filter paper and is collected in the beaker under the funnel. The impurities (particles) of soil were detained by the filter paper. This process of separating the panicles of soil from the mixture of soil and water by the filter paper is called filtration. Therefore, filtration is such a process by which solid substances can be separated from the heterogeneous mixture of solid and liquid.
After becoming the entire water of the beaker quite dry, what do you obtain? You obtain layers of white, dazzling and clean salt. Because all the impurities of the impure salt taken at the beginning was entirely eliminated by filtration with a filter paper.