558 abstracts: chemical technology 



CHEMICAL TECHNOLOGY.— r/i^ identification of "stones' in 

 glass. (Geophysical Lab. Papers on Optical Glass No. 4.) N. L. 

 BowEN. Journ. Amer. Ceramic Soc. i: 594-605. Sept. 1918. 

 The petrographic microscope is a convenient and efficient instru- 

 ment for the determination of the nature and origin of "stones" or 

 crystalline particles occurring in glass. Stones are divided into four 

 classes: (i) pot stones, (2) batch stones, (3) crown drops, (4) devitri- 

 fication stones. These classes have distinctive features of structure and 

 texture that are revealed by the microscope. Moreover, the crystalline 

 phases contained in stones can be identified by a determination of their 

 optical properties. The results of a study of stones by these methods 

 are given in this paper. N. L- B. 



CHEMICAL TECHNOLOGY.— 7/z& condition of arsenic in glass and 

 its role in glass-making. (Geophysical Lab. Papers on Optical 

 Glass No. 6.) E- T. AllEn and E. G. ZiES. Journ. Amer. Cer- 

 amic Soc. i: 787-790. Nov., 1918. 

 Analyses show that in all the glasses tested, both plate and optical 

 glasses, the major part of the arsenic present exists in the pentavalent 

 state, but nevertheless a portion exists in the trivalent state. It ap- 

 pears that arsenic trioxide is oxidized at a low temperature and the 

 product formed is stable enough to remain until a high temperature 

 is reached and the glass becomes fluid, when it slowly dissociates into 

 oxygen and arsenic trioxide, both of which aid in the fining. E. T. A. 



CHEMICAL TECHNOLOGY. — Constitution and microstnicture of silica 



brick and changes involved through repeated burnings at high 



temperature. Herbert InslEy and A. A. KlEin. Bur. Stand. 



Tech. Paper 124. Pp.31, pis. 10. 1919. 



The investigation involves a petrographic microscopic study of test 



cubes and commercial silica brick, some of which had received repeated 



burnings by use in ki]ns. Quartz, cristobalite, and tridymite are the 



main constituents. Small amounts of pseudowollastonite and glass 



are present. Long burning at temperatures slightly less than i470°C. 



causes the formation of a large percentage of tridymite. Cristobalite 



characterizes higher burned brick. Quartz first inverts to cristobalite 



in the fine grained ground mass and along cracks caused by shattering 



on heating, and then to tridymite if the temperature does not exceed 



i470°C. The Hme added in grinding aids more as a flux than as a 



bond. Most of the cementing action in the burned product comes 



from the interlocking of the quartz, cristobalite, and tridymite crystals. 



H. I. 



