Properties of Boric Acid

Boric acid, also known as Acidum Boricum, orthoboric acid and boracic acid, is a mild acid composed of a single boron, three hydrogen and three oxygen molecules. Boric acid serves many functions ranging from antiseptic applications to assisting in nuclear reactors. Boric acid in its mineral form is called sassolite, and appears in volcanic and hot spring areas. It is extracted from minerals containing boron, known as borates, using sulfuric acid.

History

Borax has been in use since ancient China where they used it in ceramic glazes. Arabian metalsmiths began using it in the eighth century in their gold and silversmithing. In 1702 William Homberg made the first boric acid which was called "Sal Sedativum Hombergi." In 1790 borate deposits were discovered in the Andes; in 1872 they were found in Nevada; and in 1881, in California's Death Valley. It was first approved for use as a pesticide in the United States in 1948.

Identification

Boric acid is visually identifiable as a white odorless solid. However, as visual identification is often the least accurate in identifying a substance with accuracy, boric acid is usually identified by its solubility in water and 170C melting point using a combination of solute separation techniques and fractional distillation. Boric acid will degrade through dehydration into metaboric acid and tetraboric acid at 171C and 300C, respectively.

Types

Under normal atmospheric pressure boric acid may appear as any of the three phases of matter--solid, liquid or gas. Also, boric acid may be crystallized chemically from its freebase form into a hydrochloric or sulfuric salt using standard chemistry crystallization procedures. Some of its mineral formations include: anhydrous boric acid, anhydrous borax, borax pentahydrate, borax decahydrate and sodium perborate.

Use

A versatile and long lived substance, boric acid and its derivatives have been used medically as an antiseptic for cuts or any other open wound. It also has been used as an antibacterial agent for the treatment of acne and yeast and fungal infections. It is commonly used as an insecticide, fertilizer component, lubricant, in glass production of LCD monitors and as control rod materials for nuclear fission reactors in pressurized water chambers.

Warning

Boric acid is mildly toxic to humans, with a median lethal dose at 2,660 mg/kg of body mass through internal ingestion or inhalation. While this median lethal dose in humans is just barely more toxic than table salt for one-time exposure it does not rule out long term toxicological effects. Research has shown that dosages as low as 32 mg/kg over a 90 day period can cause such pathologies as testicular atrophy in animals.