GASES EVOLVED FROM GLASSES 131 



tube work since such gases can be fairly readily removed by a pre- 

 liminary heating. 



Summary of Results 

 The results of our investigation may be summarized as follows: 



(1) Glasses whose compositions run high in alkali give off more 

 gas during their heat treatment than do those of lower alkali 

 content. 



(2) A definite relation appears to exist between the amount of 

 water vapor held by a glass and its alkali content. 



(3) A relation, although not as pronounced as that mentioned 

 above, appears to exist between the amount of carbon dioxide 

 held by a glass and its alkali content. 



(4) Adsorbed carbon dioxide seems to be held to glass primarily 

 by primary valence forces. 



(5) Adsorbed permanent gases seem to be held to glass primarily 

 by secondary valence forces. 



(6) Glass relatively free from absorbed gas can be produced by 

 means of heating the glass during its melting process to a 

 sufficiently high temperature. 



In conclusion the authors wish to express their thanks to Dr. J. 

 Johnston to whom they are especially indebted for assistance and 

 advice. 



BIBLIOGRAPHY 



(1) Allen, E. T. & Zies, E. G. }. Am. Coram. Soc / 739-790, 1918. 



(2) Briggs, H. Nature, 107, 285-286, 1921. 



(3) Bunsen, R., LTeber die Verdichtung der COi an blanken Glasflachen. Ann. 

 d. Phys. (3) 20\ 545-560, 1883. 



(4) — Ueber die langsame Verdichtung der COi an blanken Glasflachen 



und Kayser's Einwiirfe dagegen (3), 22, 145-152, 1884. 



(5) Ueber capillare Gasabsorption. Ann. d. Phys. (3) 24, 321-347, 



1885. 



Campbell, N. R. See Research Staff of G. E. Co. 

 (6) Campbell Swinton, A. A. The occlusion of the residual gas by the glass walls 



of vacuum tubes. Proc. Roy. Soc. A79, 134-137, 1907. 

 (7) The occlusion of the residual gas and the fluorescence of the glass 



walls of cathode tubes. Proc. Roy. Soc. A81, 453-59, 1908. 



(8) Chappius, P., Die Verdichtung der Gase auf Glasoberflachen, Ann. d. Phys. 



(3) S, 1-2), 1879. 



(9) Giesen, ]. Einige Versuche mit der Salvionischen Mikrowage. Ann. d. Phys. 



(4) 10, 830-844, 1903. 



(10) Gouv, Sur la penetration des gaz dans les parois de verre des t ubes de Crookes. 

 C. R. 122, 775-76, 1896. 



(11) Guichard, Sur les gaz degages des parois des tubes de verre. Bull. Soc. 

 Chim. Paris, (4) 9, 438-42, 1911. 



(12) Hill, S. E. The absorption of gas in vacuum tubes. Proc. Phys. Soc 

 London, 25, 35-43, 1912. 



