Isotopes

There are a total of 59 radioactive isotopes for bismuth, ranging in half-livesfrom a few milliseconds to thousands of years. At one time it was thought that there wasjust one stable isotope (Bi-209), but it was later found that Bi-209 is radioactive witha half-life of 19,000,000,000,000,000,000 years. Such a long half-life means that Bi-209 has not completely disintegrated and is still found in nature, and is thus consideredstable. In this case, Bi-209 makes up 100% of Bismuth’s natural abundance.

Origin of Name

Bismuth was known and used by the ancient alchemists along with other metals both for chemical reactions and for medical purposes. The name comes from the German bismu, which had been changed from wismu, meaning “white.”

Characteristics

Bismuth is more resistant to electrical current in its solid state than it is in its liquid form.Its thermal conductivity is the lowest of all metals, except mercury. Even though it is considereda metal-like element, it is a very poor conductor of heat and electricity.Bismuth has a characteristic similar to water. It expands when changing from the liquidphase to the solid phase. This factor makes it useful as an alloy in metals that are used to fillmolds, given that it will expand to the cast’s dimensions.

History

In early times bismuth was confused with tin and lead. Claude Geoffroy the Younger showed it to be distinct from lead in 1753. It is a white crystalline, brittle metal with a pinkish tinge. It occurs native. The most important ores are bismuthinite or bismuth glance (Bi2S3) and bismite (Bi2O3). Peru, Japan, Mexico, Bolivia, and Canada are major bismuth producers. Much of the bismuth produced in the U.S. is obtained as a by-product in refining lead, copper, tin, silver, and gold ores. Bismuth is the most diamagnetic of all metals, and the thermal conductivity is lower than any metal, except mercury. It has a high electrical resistance, and has the highest Hall effect of any metal (i.e., greatest increase in electrical resistance when placed in a magnetic field). “Bismanol” is a permanent magnet of high coercive force, made of MnBi, by the U.S. Naval Surface Weapons Center. Bismuth expands 3.32% on solidification. This property makes bismuth alloys particularly suited to the making of sharp castings of objects subject to damage by high temperatures. With other metals such as tin, cadmium, etc., bismuth forms low-melting alloys that are extensively used for safety devices in fire detection and extinguishing systems. Bismuth is used in producing malleable irons and is finding use as a catalyst for making acrylic fibers. When bismuth is heated in air it burns with a blue flame, forming yellow fumes of the oxide. The metal is also used as a thermocouple material, and has found application as a carrier for U235 or U233 fuel in atomic reactors. Its soluble salts are characterized by forming insoluble basic salts on the addition of water, a property sometimes used in detection work. Bismuth oxychloride is used extensively in cosmetics. Bismuth subnitrate and subcarbonate are used in medicine. Natural bismuth contains only one isotope 209Bi. Forty-four isotopes and isomers of bismuth are known. Bismuth metal (99.5%) costs about $250/kg.

Production Methods

Bismuth is obtained as a by-product in smelting and refining of lead, copper or tungsten ores. The metal is partially volatilized when the ore is smelted at the high temperature. Separation from copper is achieved by electrolytic refining, bismuth accumulating in the anode slimes with lead, arsenic, antimony, tellurium, and other metal impurities. All throughout the smelting and refining operations bismuth accompanies lead. It finally is removed from lead by Betterton-Kroll or Betts processes. The Betterton-Kroll process involves the addition of calcium-lead alloy or magnesium metal to lead slime, thus converting bismuth to high-melting bismuthides of calcium or magnesium, Ca3Bi2 or Mg3Bi2, respectively. These bismuthides liquate from the bath and are separated as dross. Bismuth dross is then melted in kettles forming Bi7Mg6K9 which liquates to the top of the bath and is removed from the molten lead. Treatments with caustic soda finally produce the high quality bismuth.In a modified process, potassium substitutes for calcium to form Bi7Mg6Ca9 which liquates to the top of the bath and is removed from the molten lead. The Betts process is based on electrolytic refining using a solution of lead fluorosilicate and fluorosilicic acid. While lead is deposited on the cathode, bismuth goes to the anode where it is collected with other impurity metals. It is then filtered, dried, smelted, and further refined, depending on the purity desired. Impurities are removed by adding molten caustic and zinc, and finally by chlorination.Bismuth may be obtained from other ores, too. The recovery process however, depends primarily on the chemical nature of the ores. For example, the sulfide ore requires smelting, carbon reduction, and the addition of iron (to decompose any bismuth sulfide present). Oxide ores, on the other hand, are treated with hydrochloric acid to leach bismuth from the mineral. The bismuth chloride solution is then diluted with water to precipitate bismuth oxy-chloride. The precipitate is roasted with lime and charcoal. Satisfactory recovery of the metal from its carbonate ore may be achieved by both the above techniques.Bismuth is sold in the form of rod, lump, powder, and wire.

Hazard

Bismuth is flammable as a powder. The halogen compounds of bismuth are toxic wheninhaled or ingested. Some of the salts of bismuth can cause metallic poisoning in a mannersimilar to mercury and lead.At the beginning of the twentieth century, before penicillin, bismuth compounds wereused to treat some venereal diseases. However, the treatment was generally unsuccessful.

Health Hazard

Exposures to bismuth salts are associated primarily by ingestion. Bismuth is known to cause adverse health effects. The symptoms include, but are not limited to, irritation of the eyes, skin, respiratory tract, lungs, foul breath, metallic taste, and gingivitis. On ingestion, bismuth causes nausea, loss of appetite, weight, malaise, albuminuria, diarrhea, skin reactions, stomatitis, headache, fever, sleeplessness, depression, rheumatic pain, and a black line may form on gums in the mouth due to deposition of bismuth sulfi de. Prolonged exposure to bismuth causes mild but deleterious effects on the kidneys and high concentrations of bismuth result in fatalities. Occupational exposures to bismuth occur during the manufacture of cosmetics, industrial chemicals, and pharmaceuticals. Acute exposure with over dosage of bismuth-containing drugs causes anorexia, nausea, vomiting, abdominal pain, and possibly a dry mouth and thirst. Bismuth also causes neurotoxicity. Bismuth pentafl uoride is highly toxic and causes irritation to the skin, eyes, and respiratory tract, while bismuth subnitrate causes blurred vision.

Flammability and Explosibility

Nonflammable

Potential Exposure

Bismuth is used as a constituent of tempering baths for steel alloys; in low Freezing/Melting point alloys which expand on cooling; in aluminum and steel alloys to increase machinability; and in printing type metal. Bismuth compounds are found primarily in pharmaceuticals as antiseptics, antacids, antiluetics, and as a medicament in the treatment of acute angina. They are also used as a contrast medium in roentgenoscopy and in cosmetics. For the general population the total intake from food is 5 20 μg with much smaller amounts contributed by air and water.

Carcinogenicity

An old lifetime study with rats fed 2% bismuth subcarbonate (BSC) in the diet did not show an increase of tumors or a decrease of survival.

Environmental Fate

The mechanism by which bismuth produces toxicity has not been identified. Interaction with thiol compounds has been proposed as a primary mechanism.

Shipping

UN3089 Metal powders, flammable, n.o.s., Hazard Class: 4.1; Labels: 4.1—Flammable solid.

Purification Methods

Melt it in an atmosphere of dry helium, then filter through dry Pyrex wool to remove any bismuth oxide present [Mayer et al. J Phys Chem 64 238 1960].

Toxicity evaluation

In aerated water, bismuth oxidizes; however, in an anaerobic aqueous environment, bismuth is unaffected. Similarly, in the atmosphere, bismuth is unaffected unless condensation or deposition of water occurs. Due to the inability for air and water to affect bismuth under most circumstances, bismuth tends to persist until wet or dry deposition, and therefore long-range transport is possible and likely.

Incompatibilities

Finely divided powder is highly flammable. Reacts with strong acids and strong oxidizers, chlorine, fused ammonium nitrates, iodine pentafluoride, and nitrosyl fluoride.

Waste Disposal

Dissolve in a minimum amount of concentrated HCl. Dilute with water until precipitate is formed. Redissolve in HCl. Then saturate with H2S. Filter, wash, dry and return to supplier.

Physical properties

Bismuth has unusually low toxicity for a heavy metal. Bismuth is stable to both dry and moist air at ordinary temperatures. When red hot, it reacts with water to make bismuth(III) oxide. Bismuth forms trivalent and pentavalent compounds. The trivalent compounds are more common. Many of its chemical properties are similar to those of As and Sb, although they are less toxic than derivatives of those lighter elements. At elevated temperatures, the vapors of the metal combine rapidly with oxygen, forming the yellow trioxide, Bi2O3.

Definition

A brittle pinkish metallic element belonging to group 15 (formerly VA) of the periodic table. It occurs native and in the ores Bi2S3 and Bi2O3. The element does not react with oxygen or water under normal temperatures. It can be dissolved by concentrated nitric acid. Bismuth is widely used in alloys, especially low-melting alloys. The element has the property of expanding when it solidifies. Compounds of bismuth are used in cosmetics and medicines.

General Description

All foils are mounted on a permanent support which cannot be removed without damaging the foil.

Industrial uses

Bismuth (symbol Bi) is a brittle, crystallinemetal with a high metallic luster with a distinctivepinkish tinge. The metal is easily cast butnot readily formed by working. Within a narrowrange of temperature, around 225°C, it can beextruded. Its crystal structure is rhombohedral.It is one of the few metals that expand onsolidification; the expansion is 3.3%. The thermalconductivity of bismuth is lower than thatof any metal, with the exception of mercury.Bismuth is the most diamagnetic of all metals(mass susceptibility of –1.35×106). It showsthe greatest Hall effect (increase in resistanceunder influence of a magnetic field). It also hasa low capture cross section for thermal neutrons(0.034 barn).Bismuth is playing an important role innuclear research. Its high density gives it excellentshielding properties for gamma rays whileits low thermal neutron capture cross sectionallows the neutrons to pass through. For investigationsin which it is desired to irradiateobjects, i.e., animals, with neutrons but protectthem from gamma rays, castings of bismuth areused as neutron windows in nuclear reactors.Bismuth has been proposed as a solventcoolantsystem for nuclear power reactors. Thebismuth dissolves sufficient uranium so that,when the solvent and solute are pumpedthrough a moderator (graphite), criticality isreached and fission takes place. The heat generatedfrom the fission reaction raises the temperatureof the bismuth. The heated bismuth isthen pumped to conventional heat exchangersproducing the steam power required for eventualconversion to electricity.

EXPOSURE ROUTES

inhalation, skin and/or eye contact

FIRST AID

(See procedures) Eye:Irrigate immediately Skin:Soap wash immediately Breathing:Respiratory support Swallow:Medical attention immediately