Preparation and Standardisation

For each solution the preparation and standardisation of the most commonly used strengths are described. Solutions more concentrated than those described are prepared and standardised using proportionate amounts of the reagents. Aqueous solutions less concentrated than those described are prepared by making an exact dilution of a more concentrated solution with carbon dioxide-free water. The correction factors of these solutions are the same as those from which the dilutions were prepared. Aqueous solutions of molarity below 0.1m are freshly prepared using carbon dioxide-free water.

The water used in preparing volumetric solutions complies with the requirements of the monograph for Purified Water. When used for the preparation of unstable solutions such as potassium permanganate and sodium thiosulfate, it should be freshly boiled and cooled. When a solution is to be used in an assay in which the end point is determined by an electrochemical process, the exact concentration of the solution must be determined in the same way. The composition of the medium in which a volumetric solution is standardised should be the same as that in which it is to be used.

All volumetric solutions should, if practicable, be prepared, standardised and used at 20°; if a titration is carried out at a markedly different temperature from that at which the standardisation took place, a suitable temperature correction should be made.