Chemical and Metallurgical Engineering reports in the March I937
number of the publication that shatter-proof glass with an organic instead of silicate base is being manufactured successfully by Roehm and Haas, Darmstadt. The new organic so-called "Plexiglass," based on polymerized methyl ester and abandoning the silicate foundation, promises new uses. The esters of methacrylacid are colorless liquids, which through polymerization can be made to harden into bubble-free transparent glass in any desired thickness up to two inches. "Plexiglass" is impervious to air and rain and acids, although certain organic material, acetic esters, benzol, chloroform and alcohol dissolve it. An interesting use of the material has been in the construction of models of blood vessels of human beings and animals by filling the vessels with a special solution of "Plexiglass," marketed under the trade name of "Plastoid," which polymerizes when heated to 50 to 60 deg. C. and retains the exact form of the original model, which is later dissolved and removed. The physical and chemical properties of "Plexiglass" make it suitable for use in airplanes and automobiles. Its specific weight is only I. I8 compared with silicate glass with 2.6. Tests with ~J~ to ~ inch thicknesses of organic glass and regular glass show that "Plexiglass" can stand 8 to IO times the blows of silicate glass before breaking. When it does crack, it does not splinter but breaks into a few large pieces whose edges are not sharp. The new glass, although not quite as hard as silicate glass, may be used for optical purposes and does not become yellow and is not easily scratched. An additional advantage is that it may be tooled like wood and metal; it can be cut, carved, etched, engraved, turned, ground, and polished, and two pieces can even be welded together without leaving a seam.
R. H. O.
Exterior Walls of Concrete House Completed in One Day.--(Engineering News Record, Vol. 118, No. II.) Possibilities of accelerating concrete house construction through the use of the vacuum process for removing excess water, thus permitting the prompt removal of forms, were demonstrated recently at Bethesda, Maryland, when the exterior walls for a 27 X 37 ft. bungalow consisting of two 3 in. slabs separated by a 6 in. air space, were completely poured, the forms removed and the exterior finish coat applied in one working day. The possibility of using building paper as a form material and of applying a monolithic stucco finish to concrete walls were important corollaries of the demonstration.