待测物质的500 ml溶液从450 mm的高度流到同一溶液的表面后，测量形成的泡沫体积，该方法适用于所有表面活性剂，但易水解物质的溶液不能给出可靠的结果，因为水解产物会积聚在液膜中，影响泡沫的稳定性。

After 500 ml of a solution of the substance to be tested have flowed down from a height of 450 mm onto the surface of the same solution, the volume of foam formed is measured, This method is applicable to all surface active agents, but solutions of easy-hydrolizable substances do not give reliable results because the hydrolysis products accumulate in the liquid films and affect the steadiness of the foam.