I've had luck using "Instant Ocean" for salt water aquariums.
it runs about 12.99 usd for a 10 - 15 lb bag.
it has some trace elements though depending on which type you buy.
the two leading brands are "Reef Crystals" and Instant ocean.
Hope this helps.
Amendment:
I forgot to add this, I performed this experiment once. I don't have the appropriate respirator yet to deal with the chlorine fumes. The experience was performed with a eye dropper filled with gold sponge redissolved in AuricCloride.
I put a teaspoon of instant ocean into a 150ml graduated cylinder or auric cloride then went to bed. Was surprised in the morning
I like the instant ocean Idea because It doesn't have a MSDA or watever chemical warning on it.