Just for a test, make up a does with 4 or 5 drops ...
Put in your activator, then cover the glass with a plate for the 3mins.
When you are done, take a quick whiff off of the top of the glass. It should smell like chlorine (actually it is chlorine dioxide), and it should have a yellowish color.
The other thing you can do is get chlorine test strips (like ph strips) from a local swimming pool supply store.