Actually they are specifically designed for the purpose of checking whether the level of chlorine in the solution is high enough to santize the dishes or whether more is needed. They aren't measuring the Ph level as such, just the level of sanitizing power. And most of the time the chlorine level they are checking is in a basic solution (H20 & Sodium Hypochlorite), therefore I would imagine that they would not be suitable for the purpose you inquired about. However it is entirely possible that if they were put into an acidic condition that they might respond in a way that could be correlated to the pH of the sample solution. But seeing as how there are some many easily accessible and proven methods to check the pH of a sample, why risk it? If it is worth checking, it is worth doing right. Right?? ;-) Get some Ph test strips from a supplier or at the very least...some phenol red (available at any local pool supplier, dirt cheap). You'll be much happier :-) Pyrex out of indicators