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INDUSTRIAL AND ENGINEERING CHEMISTRY
to separate corpuscles centrifugally and for vessels in which to store and freeze serum. Aside from chemical and medical uses, the calls of war on various departments of the glass industry offer contrast. Naval expansion requires radio insulators, lantern lenses, and fibrous glass for hull insulation. Expansion in aviation will call for large quantities of signal lenses and lenses for airway and airport beacons. Here fibrous glass will again be used as insulation. Side effects offer contrast in the grim tragedy of mechanized slaughter. One direct war result in terms of America and glass is that of our newest Christmas tree ornaments. These are being produced in the United States, for the first time,
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on a large-scale, low-price basis. Making Christmas tree ornaments was always a cottage industry centered in Poland, Czecho-Slovakia, and Germany. When the traditional European supply was threatened, midway in 1939, Corning began to develop methods for blowing glass ornaments. 4 i m was to make a product equally attractive, stronger, more uniform, yet inexpensive. During the past year the problem has been solved and the Wellsboro Division of the Corning Glass Works is now making enough glass ornaments to supply the whole country if need be. From blood banks to Christmas tree ornaments! Great is the gamut of war and its effects.
OPTICAL GLASS GEORGE W. MOREY Geophysical Laboratory, Carnegie Institution of Washington, Washington, D. C. PTICAL glass is a key material in our preparedness. With increasing range of gunfire comes the necessity for increasing precision of control, for fire-control instruments of greater accuracy and in greater numbers. Firecontrol instruments are optical instruments of precision, and their performance depends on the glass in their optics-socalled optical glass. Optical glass differs from ordinary glass primarily in its high quality. It is one of the purest materials of manufacture, not only in the chemical sense, but in the high degree of homogeneity which is its outstanding characteristic. It must be uniform in composition throughout; there can be no local regions of inhomogeneity, called “striae”, to deviate the light from its prescribed path. Other requirements must also be met-freedom from opaque foreign material, or “stones”, freedom from bubbles, precisely controlled annealing, and a chemical composition determined to a fraction of a per cent by the values of refractive index and dispersion specified by the lens designer. All these requirements are to be met by a material which must be melted a t a temperature so high that many of the constituents are volatile, in pots composed of the same materials as, and hence soluble in, the glass. A chunk of optical glass represents the highest perfection of the glassmaker’s art; its manufacture is a n art in itself. When we entered the war in 1917, the United States faced a shortage of optical glass which threatened to cripple our preparations. Stocks of imported glass had been practically exhausted by the previous production of fire-control instruments for the Allies. Importation was impossible. The situation had been foreseen by several groups, who were experimenting with optical glass manufacture. Of these, the Bausch & Lomb Optical Company had made most progress, but its potential production was far less than the quantity essential for our needs. Some success also had been achieved by the Spencer Lens Company, Keuffel and Esser, and the National Bureau of Standards. It is noteworthy that, although both English and French firms had long been producers of optical glass, no information or assistance was obtainable from our allies. I n the emergency the Geophysical Laboratory of the Carnegie Institution of Washington was called upon because of its wealth of experience with silicate solutions, and when the War Industries Board was formed, the director of the labora-
tory, Arthur L. Day, was placed in charge of optical glass production. The unification of control and wholehearted cooperation of all concerned resulted in the speedy solution of the technical problems which limited production, and a t the close of the mar first-class optical glass was being produced in quantity more than sufficient to meet our needs. Today the situation is far less serious, even though only one of the optical glass plants has continued in production. This is the plant of the Bausch & Lomb Optical Company, the largest manufacturers of optical instruments. Their factory has been in continuous operation, they have carried on active research on optical glass for several years, and their production capacity is adequate to supply a large part of our needs. Other sources of supply can be called upon. The Pittsburgh Plate Glass Company, one of the firms which made optical glass in the past war, has been studying the problem for some time. The optical glass plant of the National Bureau of Standards, which was moved from Pittsburgh to Washington after the war, has been producing a small quantity of excellent glass for many years. Recently, the Corning Glass Works has become interested in the manufacture of some of the more difficult types of optical glass, and their product probably is superior to any previously manufactured. We thus have one large plant in active operation and other potential sources capable of immediate expansion. Moreover, the knowledge of compositions and methods which we had to obtain by experiment, by trial and error, in 1917 is now available. The information and processes obtained or devised by the scientific group from the Geophysical Laboratory with the collaboration of the several glass manufacturers were freely published and are a matter of public record. Men with training and experience are available. Stocks on hand of optical glass are large enough to serve in an emergency until our production can be increased. The glass industry is able and eager to do its part; cooperation from industry is assured. Cooperation also is necessary from government. As was found in 1917-18, unified control is necessary to ascertain the needs of all branches of the services, to find out how much of what is needed, when, and by whom, to assure adequate and uniform specifications and methods of test, and to integrate the production of this vital key material as part of our preparedness program.
