Best remedy for cleaning VERY dirty 14K Gold rope chain. I never removed it..ever!!?

The chain is quite thick and heavy so will with-stand any sort of cleaner. I use one I got at a Department Store that has a Jewelry Dept.- in a jar & put the chain part in and left my locket out by letting it hang over the jar opening edge with the top as a stopper. She has no access to a Jewelry Dept store where she lives and cannot wear it as dirty as it is & wondered if her denture cleanser would work. I suggested Alka-Seltzer or Peroxide and a toothbrush, and a good rinse after and dry with a clean soft white cloth. Any other suggestions?? All dirt and junk already inside the chain are sealed in there with hair-spray..so should be able to withstand something at least over night. Anxiously awaiting any answers.!!!