The term 'salt of boric acid' refers to a type of chemical compound known as a borate. Borates are composed of boron and oxygen atoms, and can be found in many different forms, including borax, boric acid, and boron oxide. Boric acid is a weak acid that is often used as an antiseptic, insecticide, and preservative. The salt of boric acid is a compound formed when boric acid reacts with a base, such as sodium hydroxide or potassium hydroxide. This reaction produces a salt, such as sodium borate or potassium borate, which can be used for a variety of purposes, including cleaning, preserving food, and treating skin conditions.