1, prepare the equipment. It is necessary to prepare tray balance (including weight), measuring cylinder, beaker, glass rod, medicine spoon, funnel, filter paper, iron shelf (with iron ring), evaporating dish, alcohol lamp, crucible pliers, rubber dropper, mortar, pestle, matches and some small pieces of paper.
2. dissolve. Weigh 2g of raw salt with a tray balance (accurate to 0. 1g). Measure 10 ml of water with a measuring cylinder and pour it into a beaker. Add a spoonful of coarse salt to water with a medicine spoon and stir with a glass rod; Then add the original salt and stir with a glass rod while adding it until the original salt is no longer dissolved.
3. filter. Filtration is the most important step in the experimental operation of crude salt purification. Adjust the iron ring to a proper position, and put a beaker and a filter on it. The glass rod leans against the three layers of filter paper, the nozzle at the lower end of the funnel leans against the inner wall of the beaker, and the beaker mouth leans against the glass rod to drain water, and the edge of the liquid level is lower than the edge of the filter paper.
4. Add the solution in turn. Add BaCl2, NaOH and Na2CO3 in turn.
5. Filtering and evaporation. Pour the filtrate into an evaporating dish, heat it with an alcohol lamp to evaporate water, and cool it to obtain pure sodium chloride crystals.
6. crystallization. Waiting to evaporate into crystals.
Matters needing attention in the experiment:
1, a post. In the experiment, sticking means that the folding angle of the filter paper should be consistent with the diameter of the inner wall of the funnel, so that the wet filter paper can cling to the inner wall of the funnel without bubbles, because if there are bubbles, it will affect the filtration speed.
2, three rely on. The "three-lead" in the experiment means that when the liquid to be filtered is poured into the funnel, the beaker mouth of the beaker containing the liquid to be filtered should lean against the inclined glass rod (glass rod drainage) to prevent the liquid from splashing and the liquid to be filtered from breaking through the filter paper; It means that the lower end of the glass rod should gently lean against the three layers of filter paper to prevent the filter paper from breaking; It means that the neck of the funnel should be close to the inner wall of the receiver receiving filtrate to prevent the liquid from overflowing.
3. The second lowest. The second lowest in the experiment means that the edge of the filter paper is slightly lower than the edge of the funnel, and it is always necessary to pay attention to the fact that the filtrate level is lower than the edge of the filter paper during the whole filtration process. This can prevent impurities from directly flowing into the beaker without filtration, so that the unfiltered liquid is mixed with the filtrate, which makes the filtrate turbid and fails to achieve the purpose of filtration.