one can obtain sodium chloride from sea water by filtration, AFTER performing crystallization.
1. pour the sea water into a beaker
2. slowly and gently heat the sea water, allowing water to evaporate
3. when solid is seen at the bottom of the beaker, filter the liquid (by pouring the content of beaker into a funnel with filter paper)
4. (wash,) dry the solid (of sodium chloride)
動動腦, 轉轉彎, 方法唔啱使, 可以做到個target 啱使.
2011-12-06 16:39:45 補充：
one need not to evaporate the sea water to dryness in order to obtain sodium chloride.
a (re)crystallization will do.
c.f. commercial production of sea salt
2011-12-06 16:41:59 補充：
sodium ion and chloride ion have highest concentration in sea water, so it's safe to assume that mainly sodium chloride is produced in crystallization.
well, if you do not assume this, how can one (readily) separate ions from the bulk?