As I understand it, Benzedrex inhalers contain freebase propylhexidrine. The freebase is actually a volatile oil (similar to meth freebase) which is why it is inhaled as a vapour instead of snorted as a powder. The main acid in lemon juice is citric acid and hence the lemon juice wash of the cotton will contain propylhexidrine citrate. (perhaps a small amount fo propylhexidrine ascorbate from the vitamin C as well)
If you wanted to make the HCl salt presumably it would be as simple as rinsing the cottons with a slight excess hydrochloric acid and then evaporating the water (and excess acid) off.
If you want to get precise,
Molecular weight of propylhexidrine freebase = 155.29 g/mol
Inhaler contains 0.25g of freebase propylhex. 0.25 g / 155.29 (g/mol) = 1.61 millimoles of propylhexidrine
MW hydrochloric acid = 36.5 g/mol
1.61mmol * 36.5g/mol = 58.8 mg of HCl needed to neutralize (0.05876g)
Commercial concentrated HCl is 37% w/v
58.8mg / 37% HCl = 0.158 mL concentrated acid needed.
So, to make a crude form of propylhexidrine HCl, take some distilled water, add about 0.2 mL of concentrated HCl (check hardware stores, pool supply etc) to the distilled water, then rinse the cotton well, evaporate the water gently, and you should be left with the HCl salt.
