GB1103275A - Testing the stability of suspensions in liquid media - Google Patents

Abstract

1,103,275. Testing stability of suspensions in liquid media, electrically. NATIONAL RESEARCH DEVELOPMENT CORPORATION. May 3, 1965 [Feb. 5, 1964], No.4885/64. Heading G1N. The stability of a suspension of a substance in a liquid medium which is not highly conductive (e.g. an emulsion of oil in water) is determined by the change in the capacitance of a capacitor of which the emulsion forms the dielectric. The dielectric constant of the substance should differ appreciably from that of the liquid medium. As shown a capacitor cell comprises coaxially disposed tubular electrodes 6, 7, formed by silver deposition on two coaxial cylindrical glass walls which define an annular chamber 4 to which the test emulsion is admitted by an entry 5. The capacitor cell is connected in parallel with a variable capacitor C18 in the tuning circuit of an oscillator 16, the output of which together with the output of a stable crystal oscillator 17 is fed to a mixer. The mixer output is connected to a loudspeaker or visual indicator 20. With the space between electrodes completely filled with emulsion C18 is adjusted until the two oscillator frequencies are equal and the mixer output is zero. As the emulsion gradually separates with time into its constituents causing a change in the cell capacitance and consequent change in frequency of oscillator 16, an output signal is produced by the loudspeaker. The amount of adjustment of C18 over a measured period of time, necessary to silence the speaker, gives a measure of the stability of the emulsion. For a suspension of solid particles in a liquid the upper or lower part of the depth may be between the electrodes dependent on whether the dielectric constant of the solid particles is respectively higher or lower than that of the liquid.