A recent holiday on the beach made me ask the question ” People keep saying that you cannot drink sea water. why not? Water water everywhere but not a drop to drink. Why not? When I can eat salted nuts, when I can eat gravy which is water + salt + spices then why cannot I drink salty sea water?”
Yesterday I tried an experiment: I put a pinch of salt in a glass of water. I drank a few sips and it was okay. Hey this is just lemonade without the lemon. So I increased the salt to 1 tea spoon . This was still okay. Then I increased the concentration to 1 tablespoon in the glass of water. I could drink a few sips but it created a funny feeling on my tongue. SOmething like swelling and a desire to drink water. So I drank a few more sips. My tongue felt worse and I felt thirstier.
So I realized what was happening: I could drink the salted water but it was not quenching my thirst. It was making me even more thirstier.
Lets see what happens whan we drink a fluid : The cell walls are made of a semi permeable membrane ie some things like water can go in and out. Now imagine your cell placed in water. If you are thirsty then your cell has less water. Human cells are about .9% saline. So if you are thirsty then your cell has less water than normal. That means that the concentration of salt in the cell increases. The water goes into the cell from outside it and the salt concentration in it reaches back to normal. Its thirst is quenched. So water flows in a direction so as to create equal concentration on both sides of the membrane. This is called osmosis.
Now imagine your cell placed in pure distilled water. The inside of the cell is saltier than its surroundings. So water goes in the cell from outside. It becomes less salty than .9%. But is is still saltier than its surroundings. So more water goes in. It does not stop because equilibrium is never reached. The water in the cell keeps increasing till it bursts! So drinking distilled water is not good.
Now imagine drinking a very salty water( sea water). The concentration of salt is more outside the cell than inside. So water flows from inside the cell to outside! The cell does not get water. The salty water outside it pulls the water out of it. The cell shrinks and you become more thirsty. This can cause dehydration and even kidney failure.
So you can drink a little sea water but it will not help your thirst. It will just increase it. And you cannot survive on it.
In the words of Samuel Taylor Coleridge( from The Rime of the
Water, water, every where,
And all the boards did shrink ;
Water, water, every where,
Nor any drop to drink.
There passed a weary time. Each throat
Was parched, and glazed each eye.
A weary time ! a weary time !
How glazed each weary eye,
Go, wondrous creature! mount where Science guides:
Go, measure earth, weigh air, and state the tides:
Instruct the planets in what orbs to run,
Correct old time and regulate the Sun;