X-RAY REFLECTIVITY INVESTIGATION OF NEWTON AND COMMON BLACK FILMS

In the present paper we show that X-ray reflectivity provides a new means of studying black films of soap which are the ultimate stage of thinning soap films. We have thus solved a structural problem which dates is back over three centuries old: the Newton black film has a sandwich structure which does not contain an aqueous core but only contains a hydration layer of the polar heads. We have also investigated the thicker common black films as a function of the ionic strength and of the drainage of water on a nanometric scale.