There are taste tests for both. You can search the net.
If you are trying to get rid of mercury from Amalgam fillings, large fish, flu and some other vaccines, you might check out Andy Cutler, PhD Chemistry.
Chris Shade, PhD Chemistry is also interesting on this subject. Notice that if a guy with his credentials can make a mistake while chelating, anyone can. Cutler says he made some mistakes early in his detox process. It is a message to us to do our homework and proceed methodically. https://www.youtube.com/watch?v=zc3eTtY39eU