PHYSICAL PROPERTIES OF MASSIVE TOPAZ*

Tests on the deposit of massive topaz in Chesterfield County, South Carolina, show that the mineral has a P.C.E. of 40 and a low permanent expansion. Most of the fluorine and water are driven off between 850° and 900 ° C. The fluorine, however, carries off with it some of the iron and considerable silica. The physical properties of a fire-clay refractory in which different amounts of topaz are used to replace flint fire clay have also been investigated.     

PARTICLE-SIZE DISTRIBUTION OF GLAZES*

The particle-size distributions of experimental and commercial stains and glazes and glaze materials were determined by using the Andreasen pipette method. The variation in particle size of two porcelain glazes, raw and fritted, was correlated with the glaze working properties and certain physical properties of the glaze film, such as fluidity, microtexture, scratch-hardness, and glaze stress. The relation of grinding efficiency to length of milling time and different ball size was studied for these two glazes and also for a stain, and the color imparted by the stain at different grain sizes was noted.     

PHOSPHATES IN CERAMIC WARE: IV,PHOSPHATE GLASSES*

Phosphorus pentoxide, which was used first to improve the color of heavy flint glasses, was later recognized as a valuable constituent of optical glasses, and the excellent ultraviolet transmission and low softening points of phosphate glasses have been found recently. Glasses that have a high content of P₂O₅ have poor chemical resistivity, but this drawback is largely overcome by the addition of alumina. A possible picture of the constitution of phosphate glasses is presented, and the effect of alumina is explained. Some of the properties of the phosphate glasses have been investigated and correlated with their chemical composition and structure.     

Buchbesprechungen

Ohne Zusammenfassung     

Über das anatomische Gefüge von technisch überbeanspruchtem Holz

Zusammenfassung Der mikroskopische Aufban von durch mechanische überbean spruchung ver?ndertem Holz wird beschrieben. Zur Untersuchung gelangen; Lignostone, Druckstauchungen und Ri?fl?chen.