The actinic darkening of the colors of certain glazes and bodies is described.

The effect of the addition of various oxides on the mullitization of kaolinite was studied by chemical, microscopic, and X-ray methods. A comparative study of the chemical and the X-ray methods of mullite determination has shown that the chemical method (use of hydrofluoric acid) can yield only relative values. The use of X rays appears to give absolute results.The oxides of zinc, lithium, magnesium, iron, manganese, and molybdenum were found to be good mullite builders; sodium, potassium, titanium, and stannic oxides were poor; and boric oxide and calcium oxide were fair accelerators.

Surface-tension measurements were made on a series of moltcn glasses at 12L(H)" and 1B50°C, using the maximum bubble-pressure method. -4 basc glass was chosen with the composition of 17.4% NazO, 10.1% CaO, 72.5% SO,, or 1.4 Na,O:O.9 CaO:(i.O SiOz, t o which 0.030 gram-atom of various elements in the form of their oxides was added.An increase in surface tension was produced by Li, Si, Ca, Ra, Mn, Ni, Co, I'e, Zn, Al, Mg, Ce, and Zr. A decrease was produced by Ti, Na, B, K, Pb, and 1'. The values at 1200°C ranged from 235 dynes per centimeter for the glass containing vanadium, to 320 dynes per centinieter for the zirconium-contaiiiiiig glass; the base glass had a value of 304 dynes per centimeter. The surface-tension values at 1380°C were generally slightly less. Surface-tension results for various analyzed commercial glasses are given also for temperaturrs of lYW* and 1350OC.

The method used involved the addition of increasing amounts of kaolin to fixed amounts of feldspar and the addition of increasing amounts of quartz to fixed amounts of feldspar. All compositions were examined microscopically and the presence of undissolved kaolin was shown by the appearance of mullite needles, while the presence of undissolved quartz was shown by the presence of cristobalite. Soda feldspar is a better solvent for both quartz and clay than potash feldspar. The solution of quartz in soda feldspar starts at about 1350°C and increases with the temperature until at 1425°C. 32 parts of quartz per 100 of feldspar are dissolved. The solution of quartz in high potash feldspar does not start until 1400°C and only 4 parts are soluble at 1425°C to every 100 parts of feldspar. The solution of clay in soda feldspar starts at 1225°C and increases with the temperature until at 1425°C thirty-six parts are soluble. The solution of clay in high potash feldspar starts a t 1250°C and at 1425OC the solubility is 20.5 parts per 100 of feldspar. The zolution of quartz in porcelain bodies starts at the same temperature as it does in the pure feldspar which the body contains. The amount of solution per unit of feldspar is much greater. The general trend of one of the boundary lines in the ternary system K20-A1203-Si02 has been found.The literature on the subject is completely reviewed.

The influence of composition and temperature on the fluorescence of glasses containing uranium and glasses containing cuprous oxide and stannous oxide was investigated. Secondary cations reduce the fluorescence of uranium in the glasses studied, depending to a certain extent on the electrostatic conditions they produce in the glass structure. The intensity of fluorescence as well as the structure of the spectrum diminishes in the order of phosphate, silicate, and borate glasses of equivalent compositions, which shows that fluorescence is favored by increase of oxygen in the glass structure without increasing the interfering secondary cations. Raising the temperature greatly diminishes the intensity of the fluorescence as well as the structure of the spectrum of glasses containing uranium. The fluorescence of the glasses containing cuprous oxide and stannous oxide as activators seems to be favored by increase in lime and increase in silica. These glasses possess appreciable phosphorescence, which appears to be enhanced by increase in silica and decrease in lime. A peculiar property of this type of luminescent glass is a maximum which it exhibits in its fluorescence-temperature relationship. There are indications that electrons are set free from the excited centers (copper atoms or sinall groups of copper atoms), which wander about in the glass structure.