Terminology

Volumetric solutions are prepared according to the usual chemical analytical methods. The accuracy of the apparatus used is verified to ensure that it is appropriate for the intended use.

The concentration of volumetric solutions is indicated in terms of molarity. Molarity expresses, as the number of moles, the amount of substance dissolved in 1 L of solution. A solution which contains x moles of substance per litre is said to be x M.

Volumetric solutions do not differ from the prescribed strength by more than 10 per cent. The molarity of the volumetric solutions is determined by an appropriate number of titrations. The repeatability does not exceed 0.2 per cent (relative standard deviation).

Volumetric solutions are standardised by the methods described below. When a volumetric solution is to be used in an assay in which the end-point is determined by an electrochemical process (for example, amperometry or potentiometry) the solution is standardised by the same method. 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.

Solutions more dilute than those described below are either prepared by adapting the quantities stated or by dilution, with carbon dioxide-free water R (unless otherwise prescribed), of a more concentrated solution that has been previously standardised. In the first case, the correction factor is determined on the volumetric solution to be used in the monograph. In the latter case, the correction factor of the dilute solution is the same as that of the standardised solution from which it was prepared.

Commercially available volumetric solutions traceable to a primary standard may be used provided their titre is determined or verified prior to first use.

Titres of volumetric solutions are verified at appropriate intervals that are defined in the quality system procedures.