Salinity and the main salt ions The salinity of sea water (usually 3.5%) is made up by all the dissolved salts shown in the above table.
Interestingly, their proportions are always the same, which can be understood if salinity differences are caused by either evaporating fresh water or adding fresh water from rivers. Salinity affects marine organisms because the process of osmosis transports water towards a higher concentration through cell walls.
The main salt ions that make up 99.9% are the following: By adding the µmol in last column up, multiplied by respective valences, like: -546 468 -56.2 106.6 ....
Between 20% and 1% sea salt precipitates (Na Cl) but going further, the bitter potassium and magnesium chlorides and sulfates precipitate, which is to be avoided, unless for health reasons.
In commercial salt production, the water is led through various evaporation ponds, to achieve the desired result.
Between 100% and 50% first the calcium carbonate (Ca CO3= limestone) precipitates out, which is chalk and not desirable.
Between 50% and 20%, gypsum precipitates out (Ca SO4.2H2O), which also tastes like chalk.
Density The density of fresh water is 1.00 (gram/ml or kg/litre) but added salts can increase this. When water warms, it expands and becomes less dense. So it is possible that warm salty water remains on top of cold, less salty water.