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For producing foams or preventing foamstheoretical and empirical approaches to industrial use of surfactants are collected and explained.The physical properties exhibited by surface active materials in aqueous solution, viz., surface tension, interfacial tension, critical micelle concentration, micelle aggregation number, contact angle, spreading coefficient, etc., depend on the composition and structure of the surfactant molecule as a whole and also in part-i.e., on the composition and structure of the surfactant hydrophobe and hydrophile. Hartley considered the possession of hydrophobic and hydrophilic tendencies and their asymmetrical distribution so fundamental a property of surface active agents that he coined the word "amphipathy" for it {10). This article considers how molecular composition affects the fundamental properties that define surface activity, and tries to relate the importance of both the theoretical approach and the empirical approach to the progress of surfactant technology. Surface TensionSurfactant molecules are adsorbed at an aqueous surface because the attraction between water-water dipoles is much greater than that resulting from hydrophobe-water plus hydrophile-water attractions. The surfactant hydrophobe is "squeezed" out of solution. If we keep the same hydrophile, such as a polyalkylene oxide, and compare fluorocarbon, silicone and hydrocarbon hydrophobes, the ultimate aqueous surface tensions obtained will depend on the surface energy (van der Waals' attractions) of the hydrophobes themselves.Fluorocarbons, silicones, and hydrocarbons possess different cohesive forces (van der Waals' attractions) because of the relative deformability (polarizability) of the valence electron clouds around C-G-F. Si-C-H and C-C-H bonds (5). This difference is reflected

Analysis of the dredgings brought to the surface during the Voyage of H.M.S. “Challenger,” has shown, that in deeper water as the depth increased, the quantity of carbonate of lime shells decreased,* and as the pressure is in direct proportion to the depth under water, it was surmised that some connection existed between the pressure and the disappearance of lime shells. To ascertain if there was any truth in this surmise, Mr Murray suggested the following experiments. The results are unfortunately incomplete; nevertheless, Mr Murray thinks it advisable to publish them.