I apologize in advance for the hijack, I will answer the original question in one moment...
Mollies don't really require just salt added to the tank. They need water that is hard and high in TDS, and salt is a good way to provide this, but table salt really isn't in the answer. In that case you need MARINE salt, which contains other minerals and compounds that enrich the TDS and provide better osmotic reaction for the mollies. Also, it really is not all that necessary for MOST mollies to have salt. Most of the "fancy" varieties that are sold in stores are Poecilia sphenops or P. shenops hybrids. They have been bred in aquaria for so long that they are far removed from their wild ancestors (think carp versus goldfish.) Now, if you have P. velifera or P. latippina (I have both, and hybrids of the two) they will be larger, healthier and more robust in general if kept in brackish water. I do not believe even P. petenensis require the addition of salt, as they are found in Lake Peten, but I could be wrong on that. My P. latippina were caught for me by a fellow AC member down in FL, and were found in a stream with a SG of 1.012.
NOW - that rant is over, I am sorry but that little salt/molly myth drives me nuts, lol, the short answer is NO, your freshwater aquarium does not need an addition of salt in any concentration. Salt does have it's uses, it can be used to cure outbreaks of ich, to help speed healing in the case of injury, to help treat bacterial infections of certain natures, and to improve gill function and osmotic reaction of fish suffering from gill disease or ammonia burns in the gills. If you are not specifically treating for one of these issues (which would be better done in a smaller tank and not in a 110 gallon) then there is not reason to salt your tank.
Kristina