GB617609A - Method and means for measuring the specific surface of foam - Google Patents

Abstract

617,609. Photo - electric densitometers. CLARK, N. O. Jan. 16, 1946, No. 1500. [Class 40 (iii)] [Also in Group XXXVI] The specific surface of foam, i.e. the total surface area in a unit volume of foam, is measured by measuring the opacity of the foam flowing in a pipe-line having two glass tubes containing respectively a photo-electric cell E, Fig. 9, and a lamp C. The current through the cell E is balanced against that through a cell D illuminated by a lamp B through an optical wedge, so that the position of the wedge corresponds to the specific surface. Preferably, the lamps B, C are supplied from the same source e.g. an accumulator, on which the load is maintained constant by resistances connected across the source when the lamps are disconnected. The optical wedge preferably consists of a rotating cylinder 93, Fig. 10 (not shown), with a transparent zone whose profile is the curves of the reciprocals of the natural numbers. For very dense or highly coloured foams, the current through lamp B is reduced by a resistance 63. A flow-meter as described in Specification 598,635, [Group XXVI], may be incorporated in the same pipe-line. The expansion factor, i.e. the ratio of volume of foam to the volume of liquid it contains, may also be determined by measuring the conductivity of the foam, the current between electrodes A, Fig. 9, being compared with that between electrodes 31, 33 located in liquid from which the foam is produced.