*2.4. Silver Quantification*

Quantitative determination of the percent silver content by mass for silver oxynitrate and the Ag7NO11:SiO2 was completed in triplicate by potentiometric titration against sodium chloride (NaCl). In brief, samples (0.25 g) of the higher oxidation state silver compounds were digested in approximately 25 mL of dilute nitric acid (1:4, HNO3:H2O) overnight to liberate all silver into free Ag (I) ions in solution. This digested solution was then quantitatively transferred to a 250 mL volumetric flask and

diluted with RO water. A 5.0 mL aliquot of this solution was quantitatively transferred to a 50 mL sample vial containing 10 mL of dilute nitric acid (1:4, HNO3:H2O) and 20 mL water. The potential is measured across the analyte solution over the duration of titration with a 0.1 M NaCl titrant. The silver content of the sample volume is determined from the second derivative of the potential voltage plotted versus titrant volume, at an equimolar ratio of silver to chloride. In this manner, the mass percent silver content for silver oxynitrate and the grey Ag7NO11:SiO2 powders was determined.
