Constitution of Mixed‐Alkali Phosphate Glasses: Constitution of Lithium‐Rubidium Phosphate Glasses

In a previous study of the constitution of lithium‐sodium‐potassium phosphate glasses slight but definite cationic effects were observed. The constitution of lithium‐rubidium phosphate glasses with n̄, the number average chain length, varying from 1.25 to 9.00 was determined by paper chromatographic methods to follow the effect of substituting the rather large rubidium ion (1.47 A) for the small lithium ion (0.68 A). Systematic changes were observed; these changes, however, were numerically small. With the increase in the rubidium substitution for lithium the pyrophosphate content of the glass decreased and the tripolyphosphate content increased. Glasses with n̄ values as low as 1.5 (Li/Rb = 1/1) could be made by quenching the platinum crucible containing the melt in water. The n̄= 1.25 glass, however, devitrified when thus made. It could be prepared only by the new copper‐block‐cooled strip furnace technique.