abstracts: chemical technology 25 



CHEMICAL TECHNOLOGY.— r/z^ technique of optical glass melting. 



Clarence N. Fenner. Journ. Amer. Ceram. Soc. 2: 102-145. 



February, 1919. (Geophysical Lab. Papers on Optical Glass, 



No. 7.) 

 The course of melting operations is followed from beginning to end 

 and the essential features of procedure are described. Details of prac- 

 tice which are common to all forms of glass-making and are familiar 

 to glass-makers in general are either omitted or passed over with brief 

 descriptions, and attention is concentrated on those matters which in 

 the making of optical glass differs from that of other kinds. Because 

 of the fact that the purposes for which optical glass is to be used are in 

 many respects radically different from those of other glasses, and require 

 that exact optical and other physical properties be maintained and that 

 certain defects be eliminated, it is essential that manufacturing opera- 

 tions be controlled throughout by methods of precision. The article 

 describes the general course which must be followed to accomplish 

 these results and the effects caused by departures from the standard 

 of procedure, and takes up in more detail the principal defects which 

 are likely to occur, and considers their causes and the methods of avoid- 

 ing them. Some of the subjects discussed are : The effects of different 

 available batch-materials upon melting operations and the range of 

 choice in this matter; the necessity of close temperature regulation and 

 the results of inattention to this; fining operations, especially with 

 reference to the elimination of bubbles, and the causes and prevention 

 of bubbles in general ; variations of optical properties from requirements 

 and to what they are due; differences of procedure required for the dif- 

 ferent types of glass; stirring operations, and the manner in which they 

 should be conducted to obtain glasses relatively free from striae. 



C. N. F. 



CHEMICAL TECHNOLOGY.— y4» improved method of optical glass 

 manufacture. George W. Morey. Journ. Amer. Ceram. Soc. 

 2: 146-150. February, 1919. (Geophysical Lab. Papers on 

 Optical Glass, No. 8.) 

 Stirring is begun during the fill and is continued during the fining 

 period. Details are given of changes in procedure following this de- 

 parture from the usual schedule. The results show that with proper 

 furnace control, the customary time of manufacture of a pot of glass can 

 be reduced to 24 hours, with improvement in color due to diminished 

 pot corrosion. G. W. M. 



