從海水獲取食鹽

因為海水含其他物質，如鈣，鎂．．．．
蒸發後只能帶走水份，
而結晶的氯化鈉是純淨的

If you only evaporate the sea water to dryness, you can get salt.
BUT, there may be not pure食鹽(sodium chloride)there may be
others like calcium chloride and magnesium chloride indeed.

If you use crystallization, you will get pure 食鹽.