Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers



Last updated: January 29, 2021

What Does Precipitate Mean?

A precipitate is an insoluble solid that emerges from a liquid solution. The process of making precipitate is called precipitation. Often the precipitate emerges as a suspension.

Precipitation reactions can be used in:

  • Making pigments
  • Removing salts from water in water treatment
  • Classical qualitative inorganic analysis
  • Isolation of the products of a reaction during workup

In metallurgy, precipitation from a solid solution is also a useful way to strengthen alloys; this process is known as solid solution strengthening.

Precipitation causes heightened corrosion.


Corrosionpedia Explains Precipitate

Precipitation is the creation of a solid in a solution or inside another solid during a chemical reaction or by diffusion in a solid. When the reaction occurs in a liquid solution, the solid formed is called the precipitate.

Precipitate is referred to as a pellet after sedimentation when using a centrifuge to press it into a compact mass. The precipitate-free liquid remaining above the solid is called the supernate or supernatant. Powders derived from precipitation are known as flowers.

Precipitates can form when:

  • Two soluble salts react in solution to form one or more insoluble products
  • Temperature of a solution is lowered – The lower temperature reduces the solubility of a salt, resulting in its precipitation as a solid. The chemical that leads the solid to form is called the precipitant.
  • Using a supersaturated solution – Without sufficient force of gravity (settling) to bring the solid particles together, the precipitate remains in suspension.
  • Antisolvent is added – This radically drops the solubility of the desired product. Subsequently, the precipitate may easily be separated by filtration/decanting or centrifugation.

Precipitate development is valuable in the detection of the type of cation in a salt. For example, a barium nitrate solution will react with sulfate ions to form a solid barium sulfate precipitate, indicating that it is expected that sulfate ions are present. Precipitation reactions are also useful to extract elements, like magnesium, from seawater.

Properties of precipitates include:

  • Insoluble ionic solid products of a reaction
  • Reactions dependent on temperature or on solution concentration
  • Solids produced in precipitate reactions are crystalline and can be suspended as sediment
  • The two parts of supernatant liquid (precipitate and supernate) can be separated

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