You can get hydrochloric acid (HCl acid) at any hardware store sold as muriatic acid, HCl acid is hydrogen chloride gas dissolved in water and heroin supposedly converts back into morphine after a while when dissolved in water so you wouldn't want to let it sit to evaporate. You need a solvent that #3 dissolves in but #4 doesn't and HCl gas can dissolve in, probably the best solvent for this is diethyl ether which you can find in starter fluid (starter fluid also has heptane in it but that shouldn't affect this too much) be careful ether is highly flammable and it's fumes are explosive. You need to set up a hydrogen chloride gas generator (hydrogen chloride gas corrodes metal on contact so be careful) I believe you can do this by adding HCl acid to powdered chalk and bubbleing the gas through the ether but I do need to double check that. This solution of hydrogen chloride in ether can dissolve #3 and precipitates out #4 which you can filter off.

I am not encouraging you to do this, this is dangerous and probably more truble than its worth. Just hear for informative porpoises.