Propylene glycol is useful, no doubt, and as untoxic as glycerol, but again, this is not the question. I made a double strength Mytol-clone last year and the rest of the stock solution is yellow now after 12 months stored at room temp and still works. So a water based solution is not a major problem, but...... But mixing was not so easy, even now after 12 months I have some phenidone needles in the solution. So I was in search of an easily available solvent for the phenidone. Making a pre-dilution of the phenidone in a proper solvent other than water sounded good for me. Also weighing 0,2 grams is is not easy even with an affordable microscale. Weighing 1 gramm is easier and more precise with that scale and using a syringe for the final measuring is very precise. Maybe prediluting the phenidone in alcohol would be a useful alternative, but I guess the solution will not keep as good as a solution in PG or glycerol. I was in a drugstore some days ago, saw the glycerol and took it. Cheap, no ordering, no shipping coast, immediately availavble. Anyway, now I can make small batches of double strength Mytol stock in a couple of minutes without having to fiddle with with weighing and the proper dilution of the phenidone. That's why I did what I did and thought it could be interesting for someone else.