Drinking Salty Water

Water is the basis of all life on earth. A human has to drink 2-3 litres per day to maintain all body functions.

Was passiert, wenn ein verdurstender Schiffbrüchiger auf die Idee kommt Salzwasser zu trinken? - Er verdurstet noch schneller! Warum?

What would happen if a shipwrecked person decided to drink salt water? He would die of thirst even faster! Why? Saline solutions (also blood, saliva, potable water... contain various salts in different concentrations) show the phenomenon of so-called osmosis. Simplified, this means that two solutions with different salt contents, which are separated by a membrane (a thin layer, which is permeable for water but not for salts) always try to acquire the same salt concentration. So the water from the less concentrated solution passes through the membrane and dilutes the higher concentrated solution. This takes place until both solutions have the same salt concentration.

USuch membranes also cover the cells of our body. Now if you drink concentrated brine, the cells will exude water until the brine has approximately the same salt concentration as the blood (0.9%). So the body looses water instead of taking it up.

Only a few species of the fauna and flora are able to survive under a high salt concentration. Flamingos, for example, have a special excretive organ for secreting excessive salt crystals. Why the 'salt camels' which were discovered in China only a few months ago, are able to drink salty water without dying is still an unsolved mystery for science.

Experiments on Osmosis:

1. You need: 2 raisins, 2 grapes, salt, water, distilled water, 4 glasses

Fill 2 glasses with saturated brine and the other 2 glasses with distilled water. Now put 1 raisin and 1 grape each into a glass of brine and distilled water. After 1-2 days, the grapes will have changed a lot! The raisin in the brine looks the same as before, but the one in the distilled water has become big and juicy again. The grape in the brine has shrivelled up, whereas the grape in the distilled water remained unchanged or probably burst. Why?

2. Place some cotton wool in 2 small bowls, moisten the cotton wool, and sprinkle some cress seeds on top. After a few days, beautiful, dark green seedlings will show. If one bowl is now watered with brine and the other one with tap water, the plants in the dish with the brine will soon (after 1-2 days) wither.