Is there a way that I can set a minimum value for a function used in NDSolve? I'm using it for a related-rates chemistry problem involving concentrations. Obviously, a negative concentration is impossible, but NDSolve doesn't know or care, and the system behaves as if it is possible. I can select rate constants that prevent values from dropping below zero, but the resultant graphs are consequentially boring.
Attachment: NDSolve.png, URL: ,