註釋 Chloroform is an antimicrobial preservative which is included in the formulation of a number of official B.P. preparations. Because of its volatility, it is prone to loss by evaporation, particularly from preparations in containers which are opened and closed during use. Headspace gas chromatography was used to measure chloroform in the vapour-phase. From measurements of the relative concentrations in the liquid-phase and in the headspace above solutions in closed con- tainers, a relationship was established enabling losses to be predicted for containers having a particular fill-volume, and for containers from which aliquots are removed Hydrogen ion concentration did not have a significant influence upon the activity coefficient, but losses were influenced by ionic strength due to a 'salting-out' effect. Sodium bicarbonate, which is a constituent of some official formulae, including Magnesium Trisilicate Mixture B.P., was found to increase loss of chloroform by volatilisation Chloroform was adsorbed strongly from solution by activated charcoal. Adsorption was favoured by high pH and the process complied with the Langmuir equation. The solute was not adsorbed, however, by magnesium trisilicate, light kaolin, light magnesium carbonate and Fuller's Earth in aqueous suspension. The adsorptivity of activated charcoal could be accounted for partly by its large specific surface area, when compared with magnesium trisilicate. Activated charcoal also reduced considerably the antibacterial activity of chloroform, whereas magnesium trisi!icate was found to have only a slight effect. Because of the magnitude of losses by evaporation, chloroform is not considered to be appropriate for the preservation of preparations in multidose containers. 