About twelve years ago I bought a Zinc Plating Kit - "Zinc-Fast XL" from Tec-Nick. It has remained unopened until yesterday when I spotted it on a shelf.
Obviously contains several chemicals - Potassium Chloride, Boric Acid, Nitric Acid, Hydrochloric acid, and various organic 'brighteners' all of which I'm comfortable with handling and storing.
However one bottle - a 'Passivator' says the it contains

HYDROFLUORIC ACID

Now it may only be very diluted, but this stuff is REALLY REALLY nasty stuff - causes dreadful burns, and is absorbed by the flesh and penetrates to attack bone.
I don't want to panic, as the quantities must (I hope) be very small, and it's ?? safely ?? in a polythene sealed bottle (always used to be 'gutta percha' when I was at school), but I don't want this stuff around - I want to safely dispose of it.
The original company seem to be long gone so no advice there, so are there any chemists on the forum who can make suggestions?