Abstract: A method of improving the contacting of a gas and a liquid by injecting liquid, together with the gas in the form of substantially uniformly sized bubbles, into a vertical column of the liquid so as to introduce both a vertical downflow along the column axis and a rotational movement of the liquid-gas mixture about the axis. Preferably at least a major part of the liquid and a part of the gas is introduced tangentially near the top of the column, the remainder being introduced axially as a high velocity stream from the top of the column.

Abstract: A device for use in a bottle filling head comprises a vent tube in the form of an electrically insulating tubular member and at least two elongate electrical conductors which are substantially parallel, wherein (a) the electrical conductors are embedded in the walls of the tubular member, terminating in connectors at or close to one end of the tubular member and extending out of the opposite lower end of the tubular member; (b) at least the opposite end of the tubular member is open; and (c) the tubular member includes at least one port which permits free communication with the opposite end of the tubular member. The elongate electrical conductors are preferably arranged to act as a level detector.The invention also provides a bottle filling apparatus incorporating such a device in a bottle filling head.