The purifier is your container. Placing the velium vial with the small pieces of velium in the purifier and combining them gives you the vial of velium vapors.
Also, as I found out the hard way, the vial of velium vapors is a LORE item- you can only have one. If you have one and try to make a second, your velium vial will disappear with the purifier. Option clicking on the vial of velium vapors lists it as being NO DROP, but doesn't say LORE.