>>>Unfortunately you are not the only person who has asked me about using bleach(chlorine like in the brand name Clorox). You see, chlorine in bleach, hot tubs, swimming pools, etc. is one of the most destructive chemicals to jewelry! White gold is most drastically damaged and some yellow gold is damaged while some is not. Still, chlorine can and will discolor gold. I cannot say what the spots on your chain mean without seeing the chain; however, I suspect this is simply a tarnish caused by the chlorine in the bleach.
Tarnish caused by chlorine may affect places where the chain is soldered first. If the links look like complete loops with no gap in the loop, the links are soldered. All better chains are soldered links. Solders may be damaged and weakened by bleach. If white gold, the gold can actually fall apart! The worse damage to jewelry by chlorine is generally seen in rings with stones set into white gold prongs. The chlorine works on the stressed places in the gold, such as prong ends holding the stones in place. The prongs are bend and forced onto the stone when the stone is set and this makes stress in the metal, sort of like when a coat hanger is bent back and forth. When bent back and forth enough, the coat hanger will break. The stress in the prongs is just from one bend but that is the place chlorine starts to work. So, we see rings with the prong tips gone!
CHLORINE IN BLEACH IS NOT A WAY TO TEST FOR REAL GOLD!
Don't knock yourself for doing the bleach thing. Lots of folks have done it. One questioner actually ruined a white gold diamond ring this way and the settings had to be replaced.<<<
http://en.allexperts.com/q/Jewelry-Gems-Minerals-689/acid-test-gold.htm
If it has the potential to be valuable, why mess around? Take it to a jeweller and find out for sure.