no reason, apparently, why it should not prove to be a satisfactory general antiseptic. It is described in this paper, however, solely because its development represents a very excellent example of what is now a more or less standardized method of research for the production of a new chemical substance to take the place of an old and faulty substance.
Super-cooled Water. The viscasity of water has been determined down to -Q°C., a t which temperature it is quite fluid, and I was surprised t o find that water drops suddenly chilled (without crystallization) t o -17°C.. became hard-that is, true water glass. I n Beilby's "Aggregation and Flow of Solids," 1921, p. 195, we find: "When a small drop of water was placed on a glass slip which had previously been cooled to -12°C. it instantly froze and became like a hemispherical lens, perfectly transparent and colorless. Under the microscope i t showed no signs of crystalline structure. . ." The term "froze" is a little nmbimous, but from the context can only be taken to indicate hardening. Thus there appears to be a great change in the properties of super-cooled water I t seems unlikely that this phenomenon should have escaped between -go and -12'. notice up t o now, but I can find no reference to it. (L. Hawkes, Bedford College, Regent's Park, N. W. 1.)-Nature (London), 123,244 (Feb.16, 1929).
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Powdered Fuels for Engines. After many trials and failures, a practical and reliable internal combustion engine appears to have been developed to utilize powdered coal as fuel. Unlike the Diesel engine, states Rudolph Pawlikowski in Canadian Chemistry & Metallurgy, it compresses air and fuel a t the same time, but keeps them separated until the injection, after the compression. In the Diesel engine fuel oil must he atomized, heated, and ignited in a small fraction of an engine stroke; the new engine allows a complete stroke for these operations. The engine has been successfully operated on dust of bituminous coal, lignites, peat, wood, charcoal, rice hulls, meal, and coke. Ash disposal, of course, is one of the major problems; but in this engine the ash is so fine that the particles, even if they do get into the oil a m , rub on only one of the metal surfaces, not on both. The exhaust is odorless.-Chem. & Met., 36,287 (May, 1929).
Protection of Concrete against Corrosion. The question of the protection of concrete is reviewed by C. R. Platzmann (Chem-Ztp., Aug. 22, 1928). The chief cause of corrosion by acids and salt solutions is the presence of lime, and varieties of cement poor in this constituent have a somewhat greater resistance. A large alumina content confers a resistance to the action of sulfate solutions, hut the cost of such cements is double that of portland cement. I t suffices far such materials as tannic, lactic, and acetic adds, and for sugar solutions t o protect concrete by a coating material, the most satisfactory substance for this being pure bitumen, which has, however, the disadvantage that i t softens a t increased temperatures. Treatment of the concrete with solutions of silicofluorides gives a mechanically strong resistant surface layer. In general, the best method of protection has t o be determined for each case.-Chem. & Ind., 48.369 (April 12, 1929).
