The sea water is the salted Eau Mer S and Océan S of the Ground. “Salted” the fact indicates that it contains dissolved substances, the salts, mainly of the Chlore and Sodium. One finds 30 to 40 grams of salts dissolved for one kilogram of sea water. The salt water is opposed to the Fresh water, which contains less than one gram of materials dissolved per kilogram. The Density of sea water on the surface east of approximately 1,025 g/L, higher of 2,5% than that of fresh water because of the weight of salt and the electrostriction.

The oceans and seas occupy a volume estimated at: 1340 million km ³, which accounts for 96,4% of the capacity of the large water tanks on the surface of the Earth. This volume does not include the subterranean water (Aquifère S), whose 85% in volume are salted with various degrees.

Origin of the salt of sea water

The first scientific theories on the origin of the marine salt go back to Edmond Halley which proposes in 1715 that salt and the other minerals are brought there by the rivers: the water run-off on the surface (rainwater) and in the rivers “tears off” ions by Dissolution of the Roche S. the underground fresh water and of surface very “are thus slightly salted” because of these ions; these ions are involved to the ocean, where they remain while the evaporation involves their concentration (see the Cycle of water). Halley notes that the few lakes which do not lead to an ocean (like the Dead Sea and the Caspian Sea, to see Endoréisme) in general have a very high salinity, which it calls the “continental Météorisation” ( continental weathering ).

The theory of Halley is mainly correct. In addition to the phenomenon describes above, the Sodium was torn off with the ocean floor during the initial training of the oceans. The presence of the other ion dominating of salt, the ion Chloride, comes from the “degasification” of chloride (in the form of Hydrochloric acid) as well as other gases of the interior of the Earth, via the Volcan S and the hydrothermal mounts. The ions sodium and chloride then became the major components of the marine salt.

The average salinity of the oceans is stable since several billion years, most probably thanks to a tectonic and chemical process which removes as much salt than it does not arrive from there by the rivers. The ions chloride and sodium are thus removed by the deposits of évaporite (the “rocks saltworks”), the “gresification” (the salt deposit in pore water) and the chemical reactions with the Basalte of sea-beds. Since the creation of the oceans, sodium any more is not torn off at the ocean floors, but is captured in the layers of Sédiment S covering sea-beds. Other theories affirm that the Plate tectonics involves part of salt under the continental masses, where it goes back slowly to surface.

Characteristics

Composition

The sea water is made up of water and salts, as well as various substances in small quantity. So more of two thirds of the 94 chemical elements natural is present in sea water, the majority are it in small quantity and not easily detectable.

The Salinité is one of the most important parameters of sea water, and indicates the content dissolved salts. The average salinity of the oceans is of 35  g/l, and remains generally included/understood between 30  g/l (Atlantic Northern) and 40  g/l (Red Sea). The inland seas or comparable have a higher salinity, because the evaporation concentrates salt there. The exceptions thus relate to closed or half-closed seas, as for the extreme values of 6 g/l in surface water of the the Baltic and 330 g/l in the Dead Sea. The most salted open sea is the Red Sea.

The great characteristic of sea water is that the relative proportions of its components are appreciably constant (i.e. independent of salinity); this property was established by the Scottish chemist William Dittmar, and makes it possible to regard sea water as a solution of eleven major components in pure Eau, namely, by decreasing order of importance, the Chlore, the Sodium, the Magnésium, the Sulfate, the Calcium, the Potassium, the Bicarbonate, the Brome, the boric Acid , the Carbonate and the Fluor. The Loi of Dittmar thus makes it possible to determine the salinity of sea water by only one measurement: concentration of one of these components (for example, Cl^-) or of one of the physical properties of sea water at a given temperature (like the relative Density, the Index of refraction or the Conductivity).

Two principal salts are Na⁺ and Cl^-, which while joining form the Sodium chloride or “sea salt”, that one extracts in the saline Marais to obtain food Sel.

The dissolved gases include/understand mainly: 64% of Nitrogen, 34% of Oxygen, 1,8% of Carbon dioxide (either 60 times the proportion of this gas in the Terrestrial atmosphere).

Index of refraction

The density and thus the Index of refraction of sea water, noted N ( λ ), depend on salinity. Sea-beds (<: 3000 m) are at a temperature lower than 4°C (approximately 2°C or less) because the salt water sees its maximum of density at a lower temperature, and especially this extremum grows blurred in a constant plate before congelation.

The movement of the major oceanic masses is dominated by the variation of their salinity. They come mainly from the brine resulting from the formation from the ice-barrier (congelation of sea water) in winter with the poles, as well as cooling of surface water under the same conditions. The table below watch how N ( λ ) increases with salinity for the sodium D-lines (average: : 5893 angströms = 589,3 Nm) with 18°C.

The index of refraction is also a function of the Pression of water, but the dependence is completely weak because of the relative incompressibility of water (like all the Liquide S). In fact, on the normal ranges of the temperatures (0 - 30°C), the approximate increase in N ( λ ) is 0,000016 when the pressure of water increases by an atmosphere.

The most significant factors affecting N ( λ ) are the wavelength of the light and the salinity of water. Nevertheless, N ( λ ) exceeds of less than 1% the range indicated of the values of these variables. The not-potability of sea water explains why, on a Navire or an island in the middle of the ocean, one can “miss water”, like says it the Lament of the old sailor :

“ water, water everywhere,

And not a drop with drinking. ”

If the accidental consumption of minor amounts of sea water is not detrimental for the human body, it is not possible to survive in the long run by drinking only sea water. This belief originates in the crossing of the Atlantic of Alain Bombard, but which used also the flesh of fish and rainwater. Thus, the German doctor Hannes Lindemann which had wanted to reiterate the voyage of Bombard had shown that it was not possible to do without additional fresh water. WHO used its work for its recommendations.

The rate of Sodium chloride in the human Blood and the urine is generally around nine grams per liter (0,9% in mass), a rate which varies little. To drink sea water (of which the salt rate is of 3,5%) temporarily increases the salt concentration in blood. This salt must be eliminated, which is done by using water coming from Cellule S to urinate. The cells do not finish dying of Déshydratation, followed by the Organe S and finally the whole body.

The effect of the absorption of sea water was studied on Rat S in laboratory, while varying the sea water concentration in their drink water. As this concentration increased, the rats were to drink more and more to urinate more, until a concentration of 50%, while their thirst declined after 50%. These researchers thus recommend not to pass brutally from a fresh water consumption to a consumption of sea water (for shipwrecked men for example), but rather to gradually increase the proportion of sea water in fresh water.

The handbooks of survival in general advise not to drink sea water. For example, the Medical Aspects off Harsh Environments (“medical Aspects of hostile environments”) presents an analysis of 136 voyages in Life raft. The risk of death amounted to 39% for those which drank sea water, against 3% for those which did not drink any.

To make sea water drinkable (process of Desalination), several techniques exist. Simplest is to dilute it with drinking water until salinity is acceptable; one uses this technique in agriculture, for the irrigation. The more complex techniques, implementations in particular on the large ships, include the evaporator S with vacuum, the evaporators “flash” or the Osmose reverses.

Anecdotes

• With HongKong, more than 90% of water for the toilets comes from the sea, which obliges it with a different treatment.

• Rene Quinton, a self-educated scientist, discovered the similarity of our interior medium and sea water. He acquired in 1906 a world-famous personality while saving, by the isotonic sea water injection, of the thousands of children reached of the Choléra and he showed that the sea water transfusion could replace the blood Transfusion.

Quotations

The sea is salted because there are cods inside. And if it does not overflow, it is because providence, in its wisdom, also placed sponges there - Alphonse Allais

Sources

General references

• L.W. Tilton and J.K. Taylor, “Refractive index and dispersion off distilled toilets for visible radiation, At temperatures 0 to 60 °C”, in J. Res. Nat. Bur. Stand. , vol. 20, p. 419 (RP1085) 1938.

• E. Dorsey, Properties off Ordinary Toilets Substance in all off its Phases: Toilets-vapor, Toilets, and all the Ices , Reinhold Publishing, 1940.

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