Yeah it should be fine, plenty of people on BL reported doing their old dear departed granny's barbs and other stuff. The time I got hold of the 30something g of barbital it was sourced (not giving particulars) from some used in a biology lab, as barbital and possibly pheno, but definitely, definitely barbital, 5,5-diethylbarbituric acid, aka veronal, the very first of the barbs, as a PH buffer.
God knows how long the bulk of it had been in the lab, which I myself never saw, but that was the origin of it. My guess is the stock of barbital would probably most likely have been bought time ago, and used wherever called for. The nembutal would be fine. Lucky bastard getting hold of it you are.
And the specific pic I posted has text beside it confirming its due to use of barbs, amongst some other things such as sulfonamide antibiotics, its a leg or arm, forgot which, the other pics I'd completely ignored, actually. AFAIK the sulfonamides, whilst sulfa drugs can cause allergic reactions in a subset of people, inc. stevens-johnson/lyell syndrome which do cause widespread sloughing off of skin so I can't be sure which agent caused the burns. But barbs, when a shot is badly done, DO cause burns, this is well known, and due to high PH of the soluble salt forms used.
NEVER try IMing barbs, this is more or less guaranteed to cause serious injury.