Another important observation was that orange-brown precipitates were observed in all the simulated-crossover experiments when ferricyanide was present, even in the absence of quinone (Figure ). As these solids were also observed in the 2,6-DHAQ/ferrocyanide battery, which experienced 2,6-DHAQ signal losses, they appear to be relevant to the crossover-driven side reactions discussed above. Therefore, to better understand the formation of these solids, work was then carried out to determine their composition.