Prepare ahead of time a solution of the citric acid in water. For two bottles of syrup (8 oz
each) use 3 tablespoons of citric acid in 8 fluid ounces of water.
Add ammonia to syrup. DXM converts from hydrobromide salt to freebase and
precipitates out of water. Since it is now nonpolar it wants to go into a nonpolar solvent.
Now you add a nonpolar solvent and shake hard. Free base goes into
solution in solvent. Let solvent float to the top. Physically separate the layers. Now the
DXM is in the nonpolar layer, mix that with the acid and shake well. The DXM converts
back into the acid salt (since lemon juice has citric acid in it, we make DXM
hydrocitrate). This is so beautiful because the DXM is practically pulled across the oilwater
interface by the hydrogen ion gradient.
Now you throw out the oil layer, and the DXM is now acid salt in the lemon juice. Boil it
for a few minutes in the microwave, stir it good, so any volatile solvent that remains will
evaporate.
From: Complete Recreational Drug Handbook
https://www.scribd.com/doc/48105079/The-Complete-Recreational-Drugs-Handbook