Solution (Definition, Types)

Solution is defined as homogenous mixture of two or more non-reacting components/substances. It has its own unique properties such as composition, density, refractive index etc.

It is a homogenous mixture of two or more substances (which can be solid, liquid or gas, the three states of matter) i.e. Solution can be prepared by combination of any three states of matter. Thus, it can be of various types depending upon the state of solvent and solute.


The most common solutions includes gas in liquid (e.g. lime water, soda water), liquid in liquid (e.g. rectified spirit), solid in liquid (sugar solution) etc.

The substance dissolved in a solution is solute which are also called as analytes. It is usually present in smaller quantity. Substance in which solute is dissolved and usually present in larger quantity in solution is called solvent.

The solvent part of the solution is usually a liquid, but can be a gas. In most of them, solvent is water. Thus water is known as the universal solvent.


Types of solutions: Solutions can be classified on various basis. These includes:

  • On the basis of strength.
  • On the basis of saturation.
  • On the basis of use in lab experiments.


On the basis of strength solution can be of two types:

Dilute: Solution with relatively small amount of solute in it. A mixture of small amount of solute in large volume of solvent gives dilute solution. E.g. 0.85% NaCl solution.



Concentrated and Dilute Solution


Concentrated: Solution containing relatively large amount of solute is concentrated one. E.g. 85% NaCl solution.


On the basis of saturation, solution is of three types:

Unsaturated: A solution in which solute concentration is lower than its equilibrium solubility at a given temperature. It has less amount of solute than that of the actual amount of solvent which can be dissolved. E.g. Vinegar is an unsaturated solution of acetic acid in water.


Saturated: Solution that contains maximum amount of solute that can be dissolved in given amount of solvent at particular temperature. It has maximum concentration of a solute dissolved & additional solute will not dissolve. E.g. Soda is a saturated solution of carbon dioxide in water.

Types of solutions


Supersaturated: A solution that contains more dissolved material than that could be dissolved by solvent under given conditions. It contains more undissolved solute than saturated solution because of its tendency to crystallize and precipitate.


On the basis of use in experiments, solution can be three types:

Stock: Solution having higher concentration of solute than required in experiment. These are prepared for storage for further use and are of substances which are stable at higher concentration for several days.

It is concentrated solution that will be diluted to some lower concentration for actual use. These are used to save preparation time, conserve materials, reduce storage space, and improve accuracy with which working lower concentration solutions are prepared.


Working: Solution prepared by diluting stock solution for use in experiment. It is made for actual use in the lab and usually from diluting or combining stock or standard solutions.



Standard: Solution of known concentration. It is prepared by dissolving accurate amount of solute in precisely measured volume of solvent. These are used as reference solutions to prepare standard curve and determination of concentration of unknown solution.

It is solution of accurately known concentration prepared from a primary standard (compound which is stable, highly pure, highly soluble in water and has high molar mass to allow accurate weighing) that is weighed accurately and made up to a fixed volume.

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