ABSTRACTS 



Authors of scientific papers are requested to see that abstracts, preferably pre- 

 pared and signed by themselves, are forwarded promptly to the editors. The 

 abstracts should conform in length and general style to those appearing in this issue. 



CERAMIC CHEMIvSTRY. — Note on the mechanics of the weathering of glass. 



F. Russell v. Bichowsky. Journ. Amer. Ceramic Soc. 3: 309-312. 



April, 1020. (Geophysical Lab., Papers on Optical Glass, No. 236.) 

 The mechanism of the weathering of a glass surface by water is believed 

 to consist of the following stages: (1) true adsorption; (2) diffusion of ad- 

 sorbed water into the glass; (3) reaction with the silicates; (4) soaking up 

 of more water by the film so produced; (5) extraction of the soluble salts; 

 (()) solution of the silica skeleton. The appearance and behavior on heat- 

 ing of glasses in each of these stages are described. R. B. Sosman. 



CERAMIC CHEMISTRY.— .4 practical test of the resistance of optical glass 

 to weathering. F. Russell v. Bichowsky. Journ. Amer. Ceramic 

 Soc. 3: 296-304. April, 1920. (Geophvsical Lab., Papers on Optical 

 Glass, No. 23a.) 

 The experiments described in this paper were made in 1917 with the ob- 

 ject of getting a rapid routine method for testing the weather stability of 

 the optical glasses then being made for military purposes. The surface 

 alkali test described by Mylius was used, but its indications are not certain 

 for all types of glasses. Methods of determining the rate of solubility in 

 water, ammonia, or hydrochloric acid were also tried, but were not found 

 adaptable for routine procedures. The tests finally adopted consisted in 

 heating samples of the glass, in company with a standard glass, in water, 

 5 per cent sodium hydroxide, and 1 : 1 hydrochloric acid, at temperatures 

 of 175° or 225° C. The glasses could then be classified into 9 groups accord- 

 ing to their appearance when wet and when dry, although there is some- 

 times considerable difference in the order of stability found with the three 

 reagents used. The safest estimate is one based on the three tests taken as 

 a group. R. B. Sosman. 



CERAMICS. — The manufacture and uses of rolled optical glass. H. S. 

 Roberts and J. C. Hostetter. Journ. Amer. Ceramic Soc. 3: 750- 

 7()1. Sept., 1920. (Geophysical Lab., Papers on Optical Glass, No. 24.) 



Rolled optical glass is manufactured by a process combining the stirring 

 and earlier processes used for ordinary optical glass, with the casting and 

 subsequent processes ordinarily used in the manufacture of rolled plate glass. 

 The glass obtained is characterized by the presence of striae in the form of 

 plane, parallel films, which are in general invisible unless viewed edgewise. 

 ( )ptical systems manufactured from rolled glass should therefore be designed 

 so that the path of light rays cuts the striations in a direction that is as nearly 

 as possible normal to the direction of the striations themselves. The meth- 

 ods of manufacture and inspection are described and a discussion given of 

 the manner of forming the glass into blanks for lenses and prisms. J. C. H. 



110 



