Name: Sodium Borate
CAS No: Disodium tetraborate decahydrate [1303-96-4]
BP: Borax JP: Sodium Borate PhEur: Borax USP-NF: Sodium Borate
Borax decahydrate; boric acid disodium salt; E285; natrii tetraboras; sodium biborate decahydrate; sodium pyroborate decahydrate; sodium tetraborate decahydrate.
Disodium tetraborate decahydrate [1303-96-4]
Na2B4O710H2O 381.37
See Section 4
Sodium borate is used in pharmaceutical applications similarly to boric acid (see Boric Acid). It has been used externally as a mild astringent and as an emulsifying agent in creams.(1) It has also been used in lozenges, mouthwashes, otic preparations (0.3% w/v), and ophthalmic solutions (0.03–1.0% w/v). Sodium borate has additionally been investigated in the prevention of crystal formation in freeze-dried solutions.(2) Preparations of sodium borate in honey have historically been used as paints for the throat, tongue, and mouth, but such use is now inadvisable because of concerns about toxicity in such applications.. Sodium borate is also used in cosmetics such as moisturizers, deodorants, and shampoos.
Sodium borate occurs as white, hard crystals, granules, or crystalline powder. It is odorless and efflorescent
See Table I.
Acidity/alkalinity pH = 9.0–9.6 (4% w/v aqueous solution) Density 1.73 g/cm3 Melting point 758C when rapidly heated. At 1008C it loses 5H2O; at 1508C it loses 9H2O; and at 3208C it becomes anhydrous. At about 8808C the substance melts into a glassy state: ‘borax beads’. Solubility 1 in 1 of glycerin; 1 in 1 of boiling water; 1 in 16 of water; practically insoluble in ethanol (95%), ethanol (99.5%), and diethyl ether.
Sodium borate should be stored in a well-closed container in a cool, dry, place.
Sodium borate is incompatible with acids and with metallic and alkaloidal salts.
Sodium borate can be prepared from minerals such as borosodium calcite, pandermite, or tinkal; these are natural sodium or calcium borates. Treatment of the mineral with sodium carbonate and sodium hydrogencarbonate yields the sodium borate decahydrate. In the USA, brine from salt lakes is also an important source of sodium borate.(3)
Sodium borate has weak bacteriostatic and astringent properties. Historically, sodium borate has been used as a disinfectant in skin lotions and eye-, nose-, and mouthwashes. However, boric acid is easily absorbed via mucous membranes and damaged skin, and severe toxicity has been observed, especially in babies and children.(4) Consequently, the use of sodium borate as a disinfectant is now considered somewhat obsolete and careful use is recommended. The toxic effects of sodium borate include vomiting, diarrhea, erythema, CNS depression, and kidney damage. The lethal oral intake is approximately 20 g in adults and 5 g in children.(5) LD50 (guinea pig, oral): 5.33 g/kg(5,6) LD50 (mouse, IP): 2.711 g/kg LD50 (mouse, IV): 1.320 g/kg LD50 (mouse, oral): 2.0 g/kg LD50 (rat, oral): 2.66 g/kg
Observe normal precautions appropriate to the circumstances and the quantity of material handled; do not combine with acids.
Accepted for use as a food additive in Europe. Included in the FDA Inactive Ingredients Database (otic preparations; ophthalmic solutions and suspensions). Included in nonparenteral medicines licensed in the UK, Italy, France, Germany, and Japan. Included in the Canadian List of Acceptable Non-medicinal Ingredients.
Boric acid; sodium borate anhydrous
Commercially available sodium borate decahydrate is usually present as monoclinic prismatic crystals that become opaque on the surface in dry air. In addition to the decahydrate, a pentahydrate exists; this is also known as ‘jeweller’s borax’. The anhydrous substance is also available and is called ‘pyroborax’. The EINECS number for sodium borate is 271-536-2. The PubChem Compound ID (CID) for sodium borate is 11954323.