Sodium nitrite (8) 355 23.3 • 0.8 9 [NO~-] = 0.02-0.07M; pH = 8.65; temperature = 23 ~ "4" l~ insignificant or undetectable by cyclic voltammetric technique. ConclusionThe cyclic voltammogram of a used copper pyrophosphate solution shows a distinct tail beginning at approximately 0.65V. We have concluded that this tail is due to the oxidation of NOe-ions. The source of NO2-is the reduction of NO3-during electroplating. The concentration of NO2-can be accurately measured by cyclic voltammetric and spectroscopic techniques. Ogden and Tench (4) have found that the effective concentration of the brightener is changed in a used solution. Based upon our study, this change cannot be due to the buildup of NO2-. The effect could be due to organic impurities or to the buildup of orthopyrophosphate ( 14).

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