I proceeded to follow the rest of the step as outlined and I managed to get purified amph salt back. It's probably because I put a small amount of amph salt to test out this extraction procedure. I do have one question for the last step though, as I add H2SO4 the amph salt started to crystallize, I tested a small sample by adding more sulphuric acid than supposed to just to see what would happen. The crystals disappeared and it turned into a red-colored solution.
if I don't add enough H2SO4, then some crystals won't crystallize whereas if I add too much, it disappears and becomes red. So question is, how do I know how much H2SO4 to add for maximum yield?