I am having a very hard time finding information on determining the potency of mms and citric acid . I don't know if my chemicals are still effective, and wonder if there is anyway of finding out. You are the only one with any suggestions. I did check my mms with a brix mete and it was 18.5. I do not know what that means however. Can you elaborate any further on any testing process I can use to determine the potency of my chemicals. Can you also elaborate on the ph and how the ph no. would indicate the potency of the chemicals. Thank you.