A careful study of aqueous sodium fluoride solutions was carried out by the electrocapillary method. Detailed attention was given to the adsorption behaviour in dilute solutions and the results are compared with published work. Causes of discrepancies in interfacial tensions obtained directly and indirectly are examined, and found to be significantly reduced by application of appropriate experimental procedures, Localized hydrolysis and complexation effects of mercurous ions are proposed as sources of inconsistent double-layer results by different experimental approaches. R&um~Une etude rninutieuse des solutions de Auorure de sodium a Bte effect&e par la methode electrocapillaire. On a soigneusement &udie le comportement d'adsorption en solution dilu&e et compar6 les r&ultats aux pr&&dentes publications. Les raisons des differences entre les tensions interfaciales obtenues directement et indirectement sont analy&s et ces differenuzs reconnues notablement din&u&s en employant des techniques experimentales mieux appropri&s. L'hydrolyse locale et lea effets de la complexation des ions mercureux paraissent responsables des don&es contradictoires sur la couche double, respectivement issues de diffkrents modes d'approche exp&imentale. Zusammenfassurt~-Es wurde eine sorgf5ltige Untersuchung iiber