Water is a powerful solvent for many minerals. The salinity indicates the quantity of salt S dissolved in a liquid.
See also: Salt (chemistry)
Chemical properties
Dissolved salt modifies the properties of water, initially its capacity of Dissolution, its Densité, but also its Compressibilité, its point of Congélation and boiling, its electric Conductivité, its hardness like its viscosity or its corrosivity, and very slightly its capacity to transport the sounds and the light. The quantity of salts dissolved in a liquid modifies the osmotic Pression of this one.
Saturation
Salinity is limited to a given temperature known as threshold of saturation , with beyond which the liquid which cannot dissolve more salt, crystals are formed at the bottom of the container or in periphery of surface). The warm water can contain more dissolved salt than cool water.It is said that a water which contains many dissolved salts is " dure".
Measure salinity
Salinity is not easily estimable by direct chemical analysis, i.e. by drying and weighing of the solid residue, because certain bodies present (chlorides) evaporate at the end of the drying. Knowing that the proportions of the principal components of sea water are almost constant, the only proportioning of the one of them can give the content of all the others, and a measurement of salinity. The Ion S Chlorine, Bromine and Iode are easily measurable, for example by precipitation allowing a titration the Silver nitrate. They are enough with the analyzes. This is not worth for the zones located near the poles or of the Estuaire S, downstream from, marine source desalination plants of fresh water of increase of water saltworks of volcanic origin.Salinity since 1978 officiellemnet is measured starting from the electric conductivity of water a certain temperature and pressure. The salinity (S) of a water sample is given by the report/ratio K of the electric conductivity of this sea water sample to 15°C and the normal atmospheric pressure, with the conductivity of a potassium chloride solution in which the fraction in mass of KCl is 0,0324356, at the same temperature and even pressure. If K = 1 salinity is of 35. salinity is presented more like a report/ratio of mass. It is expressed without unit, like pH, but one still finds salinities expressed in o/oo, g/kg or psu ( practical salinity links ).
Salinity of the oceans
The water of the oceans is a solution which contains on average 35 gr/kg various salts (Sodium chloride primarily), with a very stable pH of 8,2 (slightly alkaline), but which tends to be acidified by solubilizing the CO2 anthropic in excess in the air. The Dead Sea contains much more salts, which explains why one floats there without effort, whereas the the Baltic contains some much less, which explains why it freezes more quickly. Nevertheless, except in the closed seas, one showed at the beginning of the 20th century that the proportion of the most important components remains quasi-constant, which lets think that since million years and more undoubtedly, the oceans were mixed perfectly by circulation thermohaline, with the assistance of certain species of plankton which by their movement daily newspapers and seasonal workers contribute to homogenize the thermal layers and saltworks.This indicated that in addition to circulations particular to each ocean, water circulated between the various oceans, which was confirmed by the Courantologie.
Quantities: The volume of the Océan S is estimated at 1 370 million km3. It would thus contain approximately 48 million billion tons of salts (or 95 t/m ² if one spread out this salt over the whole sphere, or 320 t/m ² if one spread out it only over the currently emerged parts).
Salinity and climate
A very salted water is denser and " coule" or plunges under a less dense water. Thus into the polar regions salt is rejected when the sea water is transformed into ice which expels the salt which then enriches thus liquid water making it still denser and making it plunge towards great sea-beds, feeding the circulation thermohaline, which plays a big role in the climatic regulation, the mixture of the oceanic layers and planetary ecology.But in the absence of dense source of water in the Pacific basic water goes up gradually from a progressive reduction in its density.
See too
External bonds
Simple: Salinity
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