Abstract: Debubbling apparatus may have many uses, for example, in the manufacture of photographic materials where bubbles are to be removed from liquid photographic emulsion prior to application of such emulsion to a supporting substrate, in the food processing industries or in confectionery manufacture where air bubbles are undesirable because they may harbour germs, or in blood transfusion apparatus where air bubbles present a potentially lethal hazard. Described herein is a debubbling apparatus which comprises a vessel having an outlet and an inlet spaced from one another longitudinally of the vessel, means for imparting rotational movement, about a longitudinal axis of the vessel to liquid passed through said vessel from said inlet to said outlet, and means for transmitting a beam of ultrasound along the axis of said vessel in the direction towards said inlet, from a location closer to said outlet than to said inlet.