No poisonous medicine, concoction or substance shall be held for sale or sold, except for lawful purposes and with proper motives and by persons competent to give the proper directions and precautions as to the use of the same; nor shall any bottle, box, parcel or receptacle of any poison be delivered to any person unless the same is marked "Poison" or to any person whom the party delivering the same has reason to think intends it for any illegal or improper use or purpose. (1976 Code § 12-45.)