1. First put the seawater into a pool, sun-salt, and when the sun is almost the same, pour out the water in the pool, replace it with new seawater, and then sun it.

2. After the crystal is obtained, the raw salt is put into water, heated with limestone or charcoal fire, so that the quicklime reacts with water to obtain calcium carbonate, and then water is added to obtain lime milk.

3. When lime milk is added to the water in which the original salt is dissolved, impurities will appear and then filtered.

4. Re-introduce carbon dioxide. If there is no carbon dioxide, it can be dried in the air for a period of time and then filtered.

5. Finally, refined salt without bitterness can be obtained by distillation.

It should be noted that the purification methods of salt may be different in different historical periods and regions. The above methods are for reference only, and it is recommended to consult relevant practitioners for more accurate guidance.