Solubility and Water
Solubility is the maximum amount of solute that a liquid can dissolve and is usually expressed in mg/L.

Being known as the universal solvent, water has a greater dilution capacity than any other known liquid. In other words, water can dissolve the widest variety of substances.

As mentioned above, solubility is usually measured in mg/L or mg/100 mL. In addition, the temperature of the water will often be added to the equation since it has a significant impact on solubility.

  • Note that "concentration" and "solubility" should not be mixed. Briefly, the concentration represents the amount of solute that has been dissolved in the solution.

Moreover, a solution is said to be saturated when the maximum concentration of solute is reached. For example, we know that the solubility of glucose in water at 20°C is 90 g per 100 g of water. So, a solution of 100ml of water with 90 g of glucose would be saturated.



As an aside, when aqueous solutions with different ionic compositions are mixed, a precipitation reaction can occur. When this happens, a precipitate is formed. Precipitate is an insoluble product that is separated from a solution due to changes in the solution.


Solubility of Solids

As briefly discussed above, changes in the temperature of water will affect the solubility of water. In the case of solids, the relationship is proportional since solubility will follow temperature: increasing temperature will increase solubility and vice versa.

Without going into details, this is due to the fact that the more the temperature increases, the more the water molecules are active, which increases the collisions between the water molecules and the solute.


Solubility of Gases

Like salt or sugar, gases can dissolve in water. Like solids, the solubility of gases can be affected by changes in the environment where the water is located. There are two main factors that can affect the solubility of gases: temperature and pressure.

Simply put, the higher the pressure, the more gas can be dissolved in the liquid. This is expressed by Henry's Law (C = kP)

With respect to temperature, the relationship between temperature and gas solubility is said to be inversely proportional since gas solubility decreases as the temperature of the water increases. Conversely, the solubility increases when the temperature decreases.

  • It is due to this phenomenon that the increase in water temperature affects the surrounding aquatic life. In more detail, the increase in water temperature decreases the concentrations of dissolved oxygen in the water, which will have an impact on the surrounding aquatic life. Therefore, the simple act of discharging warmer water into the wild can have a significant impact on the environment.

What is the Total Kjeldahl Nitrogen (TKN)?
Total Kjedldahl Nitrogen is a chemical parameter used to measure the amout of nitrogen in organic matter. It is commonly used to assess the quality of water, soil, and food products.