I have dilutions of different samples, which are made with 0.1 M $\ce{HNO3}$. Only I left them on the lab table for a few days and one turned yellow.
So my question is why would one turn yellow and not the other ones? They all have the same concentration of sample. The matrix in all the samples are the same. The difference is the concentration of $\ce{Cl-}$ in the samples. The one with the lowest concentration of $\ce{Cl-}$ turned yellow.
Any ideas why?