Salinity . It is the content of dissolved salt in a body of water , although the term is also valid to refer to the salt content in Soils . This characteristic is defined by the content of the substance of Sodium Chloride both in soil and in water.

Salinity is the most commonly used measure to refer to the salty saltiness of seawater and is defined as the total number of grams of inorganic salts dissolved in 1 kg of this type of water. This salinity varies according to the intensity of the Evaporation or the contribution of fresh water from the rivers . The average percentage that exists in the Oceans is 10.9% (35 grams for every liter of water).


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  • 1 Origin of sea salts
  • 2 Measurement of water salinity
  • 3 Changes in the salinity of the seas
  • 4 References
  • 5 The Dead Sea, the sea with the highest level of salinity
  • 6 Sources

Origin of sea salts

Since the volcanic chains located at the bottom of the ocean emerge wash with many of the components of the sea water : chlorine , sodium , bromine , iodine , carbon and nitrogen , which gradually are transformed into salts. In addition, the rivers carry the salts and minerals that they find on their way through the continents. In the oceans, the strong radiation from the Sun evaporates the waters, causing the salts to accumulate over time. In the waterMarine, along with a large number of chemical elements, are Dissolved Gases and Nutrients for ocean life .

Measurement of water salinity

In practice, salinity is difficult to measure. However, Marcet’s discovery of constancy in the proportionality of the major elements helped to overcome this difficulty. This observation, which is called “Marcet’s principle” or “the rule of constant proportions” postulates that “regardless of the fact that salinity may vary from place to place, the major elements of sea water]] in the open ocean are they are in constant proportions with each other. ”

Therefore, the determination of salinity could be done through the chemical measurement of its most important component, chloride . In this way, in general terms, chlorinity is defined as the total amount in grams of chloride ions plus bromides and iodides transformed into their chemical equivalents of chloride, contained in one kilogram of seawater.

Changes in the salinity of the seas

Salinity varies between the equator and the poles for two main factors: temperature and rainfall . The higher the temperature, the greater the evaporation, which increases the concentration of salts; on the contrary, the Rainsthey provide fresh water either directly or through rivers, helping to decrease salinity. According to these factors, the salinity on the coasts of Chile decreases from north to south. It reaches the maximum values ​​in its northern part due to low rainfall and high evaporation; towards the south, salinity is decreasing due to increased rainfall and lower temperatures. In the Antarctic territory it is even less due to the continuous melting of the ice that brings fresh water to the sea.

Satellite measuring the changes in the salinity of the seas


Salinity initially was defined as the total amount in grams of dissolved salts contained in one kilogram of seawater, if all carbonates are converted into oxides , all bromides and iodides in chlorides , and organic substances are oxidized . Around 1902 , the relationship between salinity and chlorinity was determined as follows: S ‰ = 0.03 + 1.805 Cl ‰ During the 1960s, the relationship between chlorinity and salinity was adjusted, which is given by the relationship:

S ‰ = 1.80655 Cl ‰ In 1978 , when the physical techniques to determine salinity from electrical conductivity and temperature measurements were developed, the definition of salinity was revised again. The “Practical Salinity Scale” defines salinity in terms of a relationship between the conductivities of a sample of normal seawater and that of a seawater of 35 g of salt per kilogram of seawater. Practical salinity is a reason and therefore has no units, but the name “psu” is often used, which in Spanish means “practical unit of salinity”.

The Dead Sea, the sea with the highest level of salinity

The Dead Sea, the sea with the highest level of salinity

The famous Dead Sea of Palestine is the sea with the highest salinity in the world. Its waters are extraordinarily salty, to such an extent that no living being can exist in it. The weather hot and dry Palestine does occur an evaporation very intense on the surface of the drink . But pure water evaporates , while the salt stays in the sea and the salinity of its waters increases.

This is why the waters of the Dead Sea contain not 2 or 3 percent (by weight) of salt, like most seas and oceans, but 27 or more percent. This salinity increases with depth. Therefore, a quarter of the content of the Dead Sea is formed by the salt that is dissolved in the water . The total amount of salt in this sea is estimated at 40 million tons.

The great salinity of the Dead Sea determines one of its peculiarities, which is that its waters are much heavier than ordinary sea water. Sinking in these waters is impossible. The human body is lighter than they are. The weight of our body is significantly less than that of an equal volume of very salty water and, therefore, according to the law of floating, man cannot sink in the Dead Sea , on the contrary, it floats on its surface the same as an egg in salt water (although it sinks in fresh water).


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