What is a real solution?

In pharmacy and chemistry, a solution is generally defined as a homogeneous mixture consisting of two or more chemical substances. This mixture – the solution – is formed as part of a physical process in which a solid, liquid or gaseous substance (the solvate) is dissolved by a liquid or solid solvent (solvent). In this process, it is possible that the solvent itself consists of a solution; it also forms the major part of the solution. Due to the homogeneous distribution of solutes in the solvent, they are not visible from the outside; however, they can be separated again using special filtration methods, such as reverse osmosis or nanofiltration.

Properties of a true solution

• The real solution is clear
• The substance is so finely distributed in the solvent that the particles are not visible
• Real solutions pass through porous filter material without leaving any residue behind

Example of a real solution

An example of a true solution is a homogeneous mixture of different substances in which the partitioning extends to the level of molecules, atoms, or ions. For example, in an aqueous sugar solution, the sugar molecules are evenly distributed among the water molecules such that each volume part of the solution contains an equal number of sugar or water molecules. The solution therefore has the same composition everywhere (homogeneous).

The term solution is not limited to liquids as solvents and solids as solutes. The ratio of solute to solvent is given by the concentration of the solution. As a rule, by solution is meant that which is formed by the dissolution and uniform distribution of a gaseous, liquid or solid substance in a liquid solvent.

What distinguishes a solution from a dispersion?

In the schematic classification of substances, true solution and dispersion (also called colloid) are opposed among mixtures. In colloid chemistry and process engineering, the dispersion is not a homogeneous, but a heterogeneous mixture of two or more substances, which hardly combine or dissolve in each other.

Forms of solutions and solubility

Whether a substance is soluble in a solvent (qualitative solubility) and in what quantity it is soluble (quantitative solubility) depends on its properties. When the maximum amount of the substance is dissolved in the solvent, the solution is considered saturated. If you now add more substance, it can no longer be dissolved and a bottom salt is formed.

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