Chemical Properties
White cryst. powder
Uses
Buffers; complexing or masking agent.
Hazard
Toxic by inhalation.
Potential Exposure
Borax is used as a soldering flux,
preservative against wood fungus; and as an antiseptic.
Used in ant poisons, for fly control around refuse and
manure piles, as a larvicide. It is used in the manufacture
of enamels and glazes, fiberglass insulation; sodium perborate
bleach; in tanning, cleaning compounds; for fireproofing
fabrics and wood; and in artificial aging of
wood.
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek
medical attention immediately. If this chemical contacts
the skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from
exposure, begin rescue breathing (using universal precautions,
including resuscitation mask) if breathing has
stopped and CPR if heart action has stopped. Transfer
promptly to a medical facility. When this chemical has
been swallowed, get medical attention. Give large quantities
of water and induce vomiting. Do not make an unconscious
person vomit.
Personal Protective Methods: Exposed workers should be
educated in the proper use of protective equipment and
there should be strict adherence to ventilating provisions in
work areas. Workers involved with the manufacture of
boric acid should be provided with masks to prevent inhalation
of dust and fumes.
Shipping
UN3077 Environmentally hazardous substances,
solid, n.o.s., Hazard class: 9; Labels: 9—Miscellaneous
hazardous material, Technical Name Required.
Incompatibilities
Dissolves in water forming a basic solution.
Boron dust may form explosive mixture with air.
Contact with strong oxidizers may be violent. Boron is
incompatible with ammonia, bromine tetrafluoride, cesium
carbide, chlorine, fluorine, interhalogens, iodic acid, lead
dioxide, nitric acid, nitric oxide, nitrosyl fluoride, nitrous
oxide, potassium nitrite, rubidium carbide, silver fluoride.
Waste Disposal
Borax, dehydrated: The material
is diluted to the recommended provisional limit
(0.10 mg/L) in water. The pH is adjusted to between 6.5
and 9.1 and then the material can be discharged into sewers
or natural streams.
Physical properties
White monoclinic crystal; density 1.73 g/cm3; decomposes at 75°C; soluble in water; the vapor pressure of the pure compound 1.6 torr at 20°C and that of a saturated solution 130 torr at 58°C; the pH of a 1% aqueous solution 9.24 (the pH is nearly independent of concentration); readily dissolves in alcohols.
Occurrence
Borax decahydrate occurs in nature as mineral, borax (tincal). It is one of the most common sodium borate ores. The compound has several industrial applications. The refined material is mostly used in household cleaning products. It is used to make pyrex and other borosilicate glasses. Borax is added to fertilizers in small quantities as a source of boron, as a trace nutrient for plants. High purity grade borax is used in cosmetics, toilet products and electrolytic capacitors. It also is used in fire retardants, adhesives and herbicides.
Production Methods
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.
Health Hazard
Borates are irritants of the eyes,
nose, and throat; at high concentrations ingestion
of the compounds can result in gastrointestinal
irritation, kidney injury, and even death
from central nervous system depression or cardiovascular
collapse.
Agricultural Uses
Borate is a salt of boric acid (H3BO3). There are two known types of borates - orthoborate and metaborate which are used as fertilizers. Besides these, polyborates, boric acid, calcium polyborate (colemanite), sodium tetraborate, solubor and complex borosilicate (boron frits) are also used as fertilizers to reduce boron deficiency. Borate minerals like kernite and tincal are the main sources of borax.
Borax, a source of boron, is the salt of boric acid, sodium hydroxide and sodium carbonate. Borax, otherwise called disodium tetraborate decahydrate(Na2B4O7·10H2O)is a water-soluble white compound. It occurs as a mineral in some alkaline salt deposits. The main sources of borax are borate minerals, kernite(Na2B4·4H2O),a sorite and heal(Na2B4O7·10H2O)which are purified by recrystallization. On treatment with an acid, borax gives boric acid which is absorbed as boron by plants. Borax contains 10.5 to 11.4% boron or 36.5% boric oxide (B2O3).
Borax is a supplier of micronutrient boron for plants and is applied as such or as a foliar spray. Solubor is preferred to borax for its greater solubility and because it causes minimum changes in the crystallization temperature.
Borax is a very important substance in other industries too. It is used as a metallurgical flux in glass and ceramic industries, a buffer, a mild alkaline antiseptic and a source of boron compounds.
Agricultural Uses
Solubor is a type of borate containing 20.3% boron. It is
chemically a polyborate, similar to borax, and is
represented as Na2B2O7?5H2O +Na2B10O16?10H2O. is a
finely-ground, white product specially designed for foliar,
liquid or dust applications, to correct boron deficiency.
Pharmaceutical Applications
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. 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.
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.
Safety
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. 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.
LD50 (guinea pig, oral): 5.33 g/kg
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
Carcinogenicity
Sodium borate tested negatively in the
Ames bioassay but was found to be cytotoxic to
cultured human fibroblasts.
storage
Sodium borate should be stored in a well-closed container in a cool,
dry, place.
Purification Methods
Crystallise the borate from water (3.3mL/g), keeping below 55o to avoid formation of the pentahydrate. Filter it off at the pump, wash it with water and equilibrate it for several days in a desiccator containing an aqueous solution saturated with respect to sucrose and NaCl. Borax can be prepared more quickly (but its water content is somewhat variable) by washing the recrystallised material at the pump with water, followed by 95% EtOH, then Et2O, and dried in air at room temperature for 12-18hours on a clock glass. [Becher in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I pp 794-795 1963.]
Regulatory Status
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.
