Precipitation (chemistry)

With precipitation or precipitation, the resignation of a solute from a solution by the addition of suitable substances ( precipitant) is called in chemistry. The resignation comes as a fully or partially insoluble precipitate in the form of flakes, droplets or crystalline material.

The precipitating agent can change its chemical composition or even keep. The precipitation of the precipitated solids are initially mostly microcrystalline or amorphous. With time may take place by the formation of a recrystallization stable crystal modification. These particles often increase with aging by additional agglomeration. Thus they can be better filtered or form a sediment. With the aging of the precipitates are also reduced their solubility.

The formation of the precipitate precipitate or by precipitation can be triggered in several ways:

• Precipitation reactions
• Change of pH
• Exceeding the solubility product

In organic chemistry and biochemistry are referred to specifically as precipitation, the precipitation of proteins, nucleic acids or other poorly soluble organic compounds. The change in the pH of the solution of an organic substance can lead to failures. The effect of certain salts with respect to the precipitation or, contrary, the increase in solubility is characterized by the Hofmeister series.

When wastewater flocculation is often next to the precipitation with precipitation agents for the removal of ingredients used in addition with the use of flocculants or coagulants.