What is happening to my chlorine dioxide when I add too much bleach or citric acid? I have some sodium chlorite and Chinese mystery powder which are meant to be mixed with water, then mixed together to form chlorine dioxide. I wanted to try a more food safe (and less mysterious) route for making small amounts of chlorine dioxide, so I diluted the sodium chlorite, then mixed in some bleach and a tiny bit of citric acid. I don't have a firm understanding of the reactions, but know $\ce{Cl2}$ and hypochlorous acid will react with sodium chlorite, but plain bleach may not, so the acid is to acidify the bleach and shift its equilibrium away from being hypochlorite. It worked, as evidenced by a pale yellow color. (It was very dilute, which is not a bad thing, for this chemical).
What I don't understand is that when I add more citric acid or more bleach, the color turns clear again. Either the chlorine dioxide is reacting or coming out of solution. What are the reactions with excess citric acid or bleach that might eliminate $\ce{ClO2}$?
The &quot;mystery powder&quot; was proposed to be sodium bisulfate, in a recent answer to another question. Sulfuric acid is used in one process to turn sodium chlorite into $\ce{ClO2}$; bisulfite would be slower, but should do the same.
Citric acid will acidify the sodium chlorite and sodium hypochlorite, but will itself be oxidized, perhaps all the way to $\ce{CO2}$. $\ce{HCl}$ is used to convert $\ce{NaClO2}$  and $\ce{NaOCl}$ to $\ce{ClO2}$ and citric acid could well do the same (be oxidized at the same time).
$$\ce{2 HCl + NaClO + 2 NaClO2 -&gt; 2 ClO2 + 3 NaCl + H2O}$$
$$\ce{4HCl + 5NaClO2 -&gt; 4ClO2 + 5NaCl + 2H2O}$$
Chlorite ion and hypochlorite ion are known to react rapidly to form chloride and chlorate (Lister, Can. J. Chem., 30, 879-889, 1952).
The unknown amounts of oxidizing agents and citric acid (a reducing agent) and the complex reactions make the pale yellow color a poor indicator of what might be going on. The presence of $\ce{ClO2}$ does not seem to be positively identified and might not even be needed to explain the observations.