Adding mild household acids to household bleach causes the release of chlorine gas. I'm sure Heloise mentioned it at least once in her column of household hints. Back in the day, when I had a chemistry set, back when they existed, and actually had chemicals, the test for chlorine gas was it's bleaching power -- moist dyed cloth held in the fumes would lose it's color. But that's a long way to go, for very little useful information. Just don't mix stuff with the Clorox, and you'll be better off.