Pressure of surfactants determn.

摘要

The presence or absence of surfactants which are not fixed in an aqueous solution chemically or physically by other substances in the solution is determined by a check whether or not the injection of air in the solution has resulted in the formation of a layer of froth above the soln. The liquid in a container of a washing machine can rise to a level (13). Two transparent windows (14,15) permit the passage of a beam of light from an emitter (21) through an optical system (23) to a receiver (22). The output signals are passed to a processor (24) which includes a comparator (26). This responds when froth is generated by the action of surfactants and lights up a lamp (25) when a threshold is reached. The air is added via a frit disc by a pump.