Glasses exposed to gamma radiation develop a visible absorption band similar to the F-band developed in alkali halide crystals. The function of cerium in preventing coloration of glass was studied in detail in an ultraviolet-transmitting phosphate base glass in which its characteristic absorption could be measured. When visible absorption was thus prevented, radiation still caused a strong absorption in the ultraviolet which was associated With the electronic structure of cerium. On this basis, transition 'ions of similar electronic structure were introduced. It was found that iron, manganese, cobalt, nickel, vanadium, copper, and, under certain conditions, some other elements do suppress the formation of the visible absorption band formed in the base glass by radiation while forming more or less prominent bands in other spectral regions. Thus the colorless iron phosphate glass remained colorless under radiation and could be considered to be ''protected." Conversely, with cobalt the new band which reached into the visible was relatively intense and stable, suggesting its use to indicate radiation dose.

Measurements of electrical resistance in the composition systems M2O3-SiO2, Si02-TiOz, A1203-Crz03, and MgO-NiO were made using, in general, dry-pressed disks about 3 cm. in diameter and 0.4 cm. thick and fired to 2500°C. In the Al2O3-Si02 series minimum resistance was shown by the samples containing 50% SiO2, 50% Al2O3. The resistance of A1203 was increased by the addition of small amounts of Cr203. The same effect was observed in the higher temperature range with small additions of NiO to MgO. In other instances the addition of the relatively inert SiO,, A1203, and MgO to the semiconductors TiOz, Cr203, and NiO resulted in a dilution effect. The resistance of Cr203 was decreased by the addition of a slight amount of MgO.

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A discussion is presented of the preparation of the sample specimen and the polishing, etching, and identification of phases when the technique is applied to basic and silica refractories. This method shows the relationship of high-iron slag to tridymite and cristobalite in the silica brick and it aids in the explanation of the bursting of chromemagnesite brick by iron oxide.