hydrofluoric acid: a weak poisonous liquid acid; formed by solution of hydrogen fluoride in water
acid: any of various water-soluble compounds having a sour taste and capable of turning litmus red and reacting with a base to form a salt
settlor: (law) a person who creates a trust by giving real or personal property in trust to a trustee for the benefit of a beneficiary; a person who gives such property is said to settle it on the trustee