Saturated salt solutions

Saturated salt solutions are homogeneous mixtures of distilled water and a pure salt. They can be used to generate and maintain specific relative humidity values within sealed containers. As a result, they can also be used to verify and calibrate humidity measuring instruments. The humidity value generated varies according to the salt used in the solution and (to a different extent for each salt) also as the temperature varies.

For the correct use of these products, it is therefore essential to operate in conditions of constant temperature (radiation should also be controlled: direct sunlight on the solution should be avoided before and during use).

As the name suggests, these solutions must be ‘saturated’ in order to work properly, i.e. the water they contain must have dissolved as much salt as possible. To ensure this, undissolved salt must be present in the container. The content of a saturated salt solution is therefore divided into two phases: a solid phase consisting of undissolved salt and a liquid phase consisting of salt-saturated water. If on visual inspection the two distinct phases cannot be seen, the solution is not saturated and does not generate the expected moisture.