Hygroscopicity and electrode function (pH response) of glasses as a measure of serviceability

D. Hubbard
1946 Journal of research of the National Bureau of Standards  
The pH responses of electrodes prepared from glasses of widely different composition have been compared with the h ygroscopicity of the glasses. The rcsulting data indicate that glasses of low hygroscopicity, such as the chemical glasswares a nd common types of optical glasses, give pH responses that fall appreciably below the theoretical predi cted from the Nerll~t e qu ation and are incapable of producing satisfactory electrodes. F ur ther, electrodes blown from glasses of intermediate
more » ... opicity, s uch as the common bottle and sheet glasses, give pH responses more nearly approximating the theoretical, whereas t he Corning 01 5 glaRs, whose superior pH response places it in a class hy itself, has a very high hygroscopicity. These results strongly su pport the belief that. adequate hygroscopici ty is one of the primary factors in determining the sui tahility of a glass for pH measurements. The data also suggest that the pH response might well be used as a rapid t est for the serviceability of optical glasses, i. e., t he ability to maintain a clear polished surface upon exposure to the atmosphere. For t his purpose it is necessary to determine the pH response over a range in which the "chemical durability" of the glass remains constant in order to avoid the voltage anomalies that accompany durability changes.
doi:10.6028/jres.036.031 fatcat:y6x2374rcfconafw2ngxw3q244