Let me get this out the way right away. There is no chemical that does to gold what the chemical that Warms uses. Gold is an inert metal. It doesn't react to anything. That is one reason why it is so valuable and so widely used.
In the novel "Sisters Brothers" Eli and Charlie are trying to hunt down Morris and Warms. Morris and Warms supposedly have a special gold hunting chemical formula that identifies the location of gold in rivers. The special chemical, once poured into a river, reacts with the water and gold and causes the gold to glow. That makes it easier to find and extract, since a man gold panning that river knows exactly where to pan. The problem with this mythical chemical is that it is extremely harmful to humans and causes severe chemical burns on skin.