Volume-active agents

For powders and granular solids, there are two types of antistatic agents surface- and volume-active additives. Surface-active agents, which increase the surface conductivity of individual particles, are effective because triboelectric charge is always situated on the surfaces of individual particles. Most if not all surface-active agents are hygroscopic and thus attract a thin film of water to the surface it is this moisture that is responsible forthe increased surface conduction (van Drumpt, 1991). The effective bulk resistivity of the particles % -may be estimated by assuming that the particles are spherical and of radius R (Jones, 1995). 

Surface active agent Concentration (% by wt of cement) Air content (% by volume) Specific surface area of bubble (mm2 mm-2) Computed spacing factor (mm)... 

High doses of osmotically active agents produce prompt bowel evacuation (purgation) within 1-3 hours. The rapid movement of water into the distal small bowel and colon leads to a high volume of liquid stool followed by rapid relief of constipation. The most commonly used purgatives are magnesium citrate and sodium phosphate. 

J.M. Corkill, J.F. Goodman and T. Walker, Partial molar volumes of surface-active agents in aqueous solution, Trans. Faraday Soc. 63 (1967) 786-772. 

Any one of a series of effects caused by hormonally-active agents that alter the homeostatic function of hormone or physiological system under the control of hormone(s). Volume 1(14), Volume 2(1). 

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