Specific steps:
1. Preparation equipment: tray balance, measuring cylinder, beaker, glass rod, medicine spoon, funnel, iron shelf (with iron ring), evaporating dish, alcohol lamp, crucible pliers, rubber-tipped dropper, filter paper, scissors, matches and paper.
Step 2 dissolve
Weigh 5g of raw salt (accurate to 0. 1g) with a tray balance. Measure 10ml of water with a measuring cylinder and pour it into a beaker.
Step 3: Filter.
Filter according to the method described in basic operation 6 of chemical experiment. Carefully observe the residue on the filter paper and the color of the filtrate. When the filtrate is still turbid, it should be filtered again.
If the filtrate is still turbid after filtering twice, the experimental device should be checked and the reasons should be analyzed, such as the damage of filter paper, the liquid level in the funnel is higher than the edge of filter paper during filtering, and the instrument is unclean. After finding out the cause, we should re-operate.
Step 4 evaporate
Pour the clarified filtrate into an evaporating dish. Place the evaporating dish on the iron ring of the iron frame and heat it with alcohol lamp. At the same time, the filtrate was continuously stirred with a glass rod.
When a large number of solids appear in the evaporating dish, stop heating. Evaporating the filtrate by using the waste heat of the evaporating dish.
5, weighing calculation
Transfer the solid to the paper with a glass rod, weigh it and recycle it to the container designated by the teacher. Compare the salt state before and after purification, and calculate the refined salt output.
Extended data
Experimental purpose
1, master the operation skills of dissolution, filtration and evaporation.
2. Understand the chemical principle of separating mixtures by filtration.
3. The application of experiential filtering principle in social practice such as life and production.
Experimental principle
The crude salt contains insoluble impurities such as precipitate, and Ca2+, Mg2+ and SO4 2-? Insoluble impurities can be removed by dissolution and filtration, and then the water is evaporated to obtain pure refined salt.
Baidu encyclopedia-crude salt purification