Chemical Properties
Barium is a silvery-white metal. It exists in nature only in ores containing mixtures of ele-
ments. The important combinations are peroxide, chloride, sulfate, carbonate, nitrate, and
chlorate. The pure metal oxidizes readily and reacts with water, emitting hydrogen. It com-
bines with other chemicals such as sulfur or carbon and oxygen to form barium compounds.
Barium compounds are used by the oil and gas industries to make drilling muds. Barium
attacks most metals with the formation of alloys; iron is the most resistant to alloy formation.
Barium forms alloys and intermetallic compounds with lead, potassium, platinum, mag-
nesium, silicon, zinc, aluminum, and mercury. Barium compounds exhibit close relation-
ships with the compounds of calcium and strontium, which are also alkaline earth metals.
Doctors sometimes use barium sulfate to perform medical tests and to take x-rays of the
gastrointestinal tract. Twenty-i ve barium isotopes have been identii ed.
138Ba is the most
abundant; the others are unstable isotopes with half-lives ranging from 12.8 days for
140Ba
to 12 sec for
143Ba. Two of these isotopes,
131Ba and
139Ba, are used in research as radioactive
tracers. The general population is exposed to barium through air, drinking water, and food.
General Description
Barium alloy, pyrophoric is mixture of barium and other metals or nonmetallic elements to improve the specific usefulness of barium. Barium alloys are a solid and can ignite spontaneously in contact with air. This material is toxic and products given off in fire could be very toxic.
Reactivity Profile
Alloys containing a substantial amount of barium react violently with acids [Lab. Gov. Chemist 1965].
Air & Water Reactions
Finely divided metal powder is pyrophoric, ignites spontaneously in air [Bretherick 1979 p. 170-171]. Alloys containing a substantial proportion of barium rapidly decomposed water. The heat of the reaction is sufficient that the evolved hydrogen may ignite [Lab. Govt. Chemist 1965].
Hazard
Flammable (pyrophoric) at room tem-
perature in powder form; store under inert gas,
petroleum, or other oxygen-free liquid. When
heated to approximately 200C in hydrogen, barium
reacts violently, forming BaH2. Eye, skin, and gas-
trointestinal irritant, and muscular stimulant. Ques-
tionable carcinogen.
Health Hazard
Fire will produce irritating, corrosive and/or toxic gases. Inhalation of decomposition products may cause severe injury or death. Contact with substance may cause severe burns to skin and eyes. Runoff from fire control may cause pollution.
Health Hazard
The health effects of barium compounds depend on how well the compound dissolves
in water or in the stomach contents. Barium compounds that do not dissolve well, such
as barium sulfate, are considered not harmful. Barium carbonate dust and barium oxide
dust have been reported to be a bronchial irritant. While barium carbonate is a dermal
irritant, barium oxide is a nasal irritant. Occupational workers exposed to barium dust,
usually in the form of barium sulfate or carbonate, often develop a benign pneumoco-
niosis also called “baritosis.” The effect of baritosis has been shown to be reversible and
has not caused any kind of severe pulmonary adverse effect. Barium compounds that
do not dissolve in water are considered safe. However, the health effects of the different
barium compounds depend on the degree of their water solubility. The compounds that
dissolve well in water are known to cause harmful health effects when ingested in high
levels. Symptoms of poisoning include stomach irritation, brain swelling, muscle weak-
ness, liver and kidney damage, adverse effects to the heart, increased blood pressure,
changes in heart rhythm, effects on the spleen, difi culties in breathing, and swelling of
the brain. Exposures to high concentrations of barium through food and drinking water cause gastrointestinal disturbances. Barium causes vomiting, abdominal cramps, diar-
rhea, difi culties in breathing, increased or decreased blood pressure, numbness around
the face, and muscle weakness, changes in heart rhythm or paralysis, and possibly death.
Animals exposed to barium over long periods showed kidney damage, decreased body
weight, and fatal injury. Ingestion of large amounts of barium chloride (2 and 4 g) causes
fatal injury, because barium ions paralyze the heart. Acute poisoning with barium causes
nausea and diarrhea, cardiac problems, and muscular spasms, as well as cardiac arrest.
Thus, barium, at concentrations normally found in our environment, does not pose any
signii cant risk for the general population. However, for specii c subpopulations and
under conditions of high barium exposure, the potential for adverse health effects should
be taken into account.
Potential Exposure
Metallic barium is used for removal of
residual gas in vacuum tubes and in alloys with nickel, lead,
calcium, magnesium, sodium, and lithium. Barium compounds
are used in the manufacture of lithopone (a white
pigment in paints), chlorine, sodium hydroxide, valves, and
green flares; in synthetic rubber vulcanization; X-ray diagnostic
work, glassmaking, papermaking, beet-sugar purification;
animal and vegetable oil refining. They are used in the
brick and tile, pyrotechnics, and electronics industries. They
are found in lubricants, pesticides, glazes, textile dyes and
finishes; pharmaceuticals; in cements which will be exposed
to saltwater; and barium is used as a rodenticide, a flux for
magnesium alloys, a stabilizer and mold lubricant in the rubber
and plastics industries, an extender in paints; a loader for
paper, soap, rubber, and linoleum; and as a fire extinguisher
for uranium or plutonium fires.
Fire Hazard
Flammable/combustible material. May ignite on contact with moist air or moisture. May burn rapidly with flare-burning effect. Some react vigorously or explosively on contact with water. Some may decompose explosively when heated or involved in a fire. May re-ignite after fire is extinguished. Runoff may create fire or explosion hazard. Containers may explode when heated.
First aid
Move victim to fresh air. Call 911 or emergency
medical service. Give artificial respiration if victim is not
breathing. Do not use mouth-to-mouth method if victim
ingested or inhaled the substance; give artificial respiration
With the aid of a pocket mask equipped with a one-way
valve or other proper respiratory Medical device.
Administer oxygen if breathing is difficult. Remove and isolate
contaminated clothing and shoes. In case of contact with
substance, immediately flush skin or eyes with running
water for at least 20 minutes. For minor skin contact, avoid
spreading material on unaffected skin. Keep victim warm
and quiet. Effects of exposure (inhalation, ingestion or skin
contact) to substance may be delayed. Ensure that medical
personnel are aware of the material(s) involved and take precautions
to protect themselves. Medical observation is
recommended for 24 to 48 hours after breathing overexposure,
as pulmonary edema may be delayed. As first aid for
pulmonary edema, a doctor or authorized paramedic may
consider administering a drug or other inhalation therapy.
Shipping
UN1400 Barium, Hazard Class: 4.3; Labels:
4.3—Dangerous when wet material. UN1854 Barium alloys,
pyrophoric, Hazard Class: 4.2; Labels: 4.2—Spontaneously
combustible material. UN1564 Barium compound, n.o.s.,
Hazard Class: 6.1; Labels: 6.1—Poisonous materials.
Incompatibilities
Barium powder may spontaneously
ignite on contact with air. It is a strong reducing agent and
Barium 337
reacts violently with oxidizers and acids. Reacts with water,
forming combustible hydrogen gas and barium hydroxide.
Reacts violently with halogenated hydrocarbon solvents,
causing a fire and explosion hazard.
Waste Disposal
Barium in solution (see spill
handling) may be precipitated with soda ash and the sludge
may be landfilled.
Physical properties
Barium is the fifth element in group 2 (IIA) of the alkali earth metals and has most of theproperties and characteristics of the other alkali earth metals in this group. For example, theyall are called alkaline earths because, when first discovered, they exhibited both characteristicsof alkaline (basic) substances and characteristics of the earth from which they came. Ancienthumans did not know they were metals because their metallic forms do not exist in nature.Barium is a silvery metal that is somewhat malleable and machineable (can be worked on alathe, stretched and pounded). Its melting point is 725°C, its boiling point is about 1640°C,and its density is 3.51 g/cm3. (The accurate figures for its properties are difficult to determinebecause of barium’s extreme activity—the pure metal will ignite when exposed to air, water,ammonia, oxygen, and the halogens.
Isotopes
Naturally occurring barium is a mixture of seven stable isotopes: barium-138 (71.66%), barium-137 (11.32%), barium-136 (7.81%), barium-135 (6.59%), barium-134 (2.42%), barium-130 (0.101%), and barium- 132 (0.097%). About six times this many radioactive isotopes have been prepared with mass numbers ranging from 114 to 153. Of the 40 isotopes known, most are highly radioactive and have half-lives in the several milliseconds to a few days range. The only notable exceptions are 133Ba with a half-life of 10.51 years, 128Ba (2.43 days), 141Ba (11.50 days) and 140Ba (12.75 days).
Origin of Name
The name barium is derived from the Latin word barys, which means
“heavy.
Characteristics
When barium burns in air, it produces barium oxide (2Ba + O2 → 2BaO). When metallicbarium burns in water, it forms barium hydroxide [Ba + 2H2O → Ba(OH)2 + H2↑]. Severalbarium compounds burn with a bright green flame, which make them useful for fireworks.Barium is more reactive with water than are calcium and strontium. This is a result of thevalence electrons’ being further from the positive nucleus. Therefore, barium is more electronegative than the alkali earth metals with smaller nuclei.In powdered form, it will burst into a bright green flame at room temperature.
Production Methods
The minerals are BaSO4 and BaCO3. Metal barium is obtained by reducing the barium oxide at a high temperature in vacuum with Al or Si or by doing electrolysis with the Hg cathode and evaporating Hg of amalgam formed at the process slowly to segregate Ba. To obtain vacuum evaporated films, direct heating with the conical basket of W, Ta, Mo, Nb, Ni, Fe, chromel, etc., or with the boat of Ta, Mo is used. Ba reacts with alumina. The rate of evaporation is 2.28×10-4 g/cm2 s with the evaporation temperature of 629 ℃.
Purification Methods
Barium is cleaned by washing with diethyl ether to remove adhering paraffin, then filed in an argon-filled glove box, washed first with ethanol containing 2% conc HCl, then with dry ethanol. It is dried in a vacuum and stored under argon [Addison et al. J Chem Soc 3868 1962]. It has also been purified by double distillation under 10mm of argon pressure.
Industrial uses
Barium (symbol Ba) is a metallic element thatoccurs in combination in the minerals witheriteand barite, which are widely distributed. Themetal is silvery white in color and can beobtained by electrolysis from the chloride, butit oxidizes so easily that it is difficult to obtainin the metallic state. Its melting point is 850°C,and its specific gravity 3.78. The most extensiveuse of barium is in the form of its compounds.The salts that are soluble, such as sulfide andchloride, are toxic. An insoluble, nontoxic bariumsulfate salt is used in radiography. Bariumcompounds are used as pigments, in chemicalmanufacturing, and in deoxidizing alloys of tin, copper, lead, and zinc. Barium is introducedinto lead-bearing metals by electrolysis toharden the lead.Barium is also a key ingredient in ceramicsuperconductors.
Environmental Fate
Ingestion of toxic doses of barium affects the muscles, especially
the heart. Barium has a digitalis-type effect on the heart.
Ventricular fibrillation and slowed pulse rate are noted. This
may be related to barium’s tendency to displace potassium; the
resulting potassium deficiency causes muscle weakness.
storage
Color Code—Yellow Stripe (strong reducingagent): Reactivity Hazard; Store separately in an area isolated from flammables, combustibles, or other yellow codedmaterials. Barium metal should be stored in a dry area, separated from halogenated solvents, strong oxidants, acids, intightly-closed containers under an inert gas blanket, petroleum, or oxygen-free liquid. Rubber gloves, rubber protective clothing and apron, goggles and gas-filter mask shouldbe worn when working in a barium storage area.
Structure and conformation
The space lattice of Barium belongs to the cubic system, and its body-centered cubic lattice has a lattice constant of a=0.5009 nm.
Toxicity evaluation
Barium is a highly reactive metal that occurs naturally only in
a combined state. The element is released to environmental
media by both natural processes and anthropogenic sources.
Barium is released primarily to the atmosphere as a result of
industrial emissions during the mining, refining, and production
of barium and barium chemicals, fossil fuel combustion,
and entrainment of soil and rock dust into the air. In addition,
coal ash, containing widely variable amounts of barium, is also
a source of airborne barium particulates. Most barium released
to the environment from industrial sources is in forms that do
not become widely dispersed. In the atmosphere, barium is
likely to be present in particulate form. Although chemical
reactions may cause changes in speciation of barium in air, the
main mechanisms for the removal of barium compounds from
the atmosphere are likely to be wet and dry depositions.
