There are a lot of videos and instructions on the net and youtube (watch NileRed and Nurdrage for example) about distilling stuff. It's a standard method in chemistry.
The remainder would be various chloride salts, like tin, led, zinc or iron chloride. The stuff you dissolved from the starting material. If you can't find any usage of it then it's waste. Treat it properly as it probably is contaminated with lead and quite toxic.
Göran