[nextpauling]

I am proposing an experiment to study the kinetics of aspirin hydrolysis in basic aqueous solution.  I want to do temperature variation to find an activation energy, but changing the temperature is probably going to change the pH of the buffer.  I am probably going to use the tris buffer, but that's tentative.  Does anybody know a good method for keeping pH constant while varying temperature?  Also if anybody knows a buffer with a small temperature dependence that would be great.  Thanks!