1st of all your statement is wrong, amphetamine HCl can be made in the form of crystals too, just not with aqueous HCl... that's why i said you have to use HCl gas, 37% HCl will result in a mess (if you still don't get it, bubble dry HCl gas into a solution of amphetamine base in a solvent). I don't know why anyone would go for the HCl salt in the first place, so if you wanna know ask the guy who suggested 37% HCl. I'm pretty sure that if you ask him nicely, he will share his patent about speed slime from aqueous HCl with you. 2nd I thought that everyone who's trying to give advice already knows what the sulphate and phosphate salts are, sry that i didn't mention several salts while having a Conversation about the hydrochloride. 3rd yes the hydrochloride is hygroscopic, but you don't have to treat it like it's Raney Nickel. A second normal air exposure wont turn it into a puddle.