Barium
Alchemists in the early Middle Ages found smooth pebble-like stones of mineral baryte near Bologna, Italy. These stones were called Bologna stones because they glowed for years after exposure to light. V. Casciorolus described these phosphorescent properties in 1602 when heating barium minerals with organics. Carl Scheele determined that baryte contained a new element in 1772 but could not isolate it as metal. Johan Gottlieb Gahn isolated barium oxide two years later in similar studies. Guyton de Morveau first called oxidized barium barote before Antoine Lavoisier changed the name to baryte. English mineralogist William Withering noted a heavy mineral in lead mines of Cumberland known today as witherite. Sir Humphry Davy first isolated metallic barium by electrolysis of molten barium salts in 1808 in England. Davy named the element after baryta using the -ium ending to signify a metallic element. Robert Bunsen and Augustus Matthiessen obtained pure barium by electrolysis of a molten mixture of barium chloride and ammonium chloride.
Barium is a soft silvery-white metal with a slight golden shade when ultrapure. The silvery-white color vanishes rapidly upon oxidation in air yielding a dark gray layer containing the oxide. Barium has a medium specific weight and high electrical conductivity. At room temperature and pressure, barium metal adopts a body-centered cubic structure with a barium-barium distance of 503 picometers. It expands with heating at a rate of approximately 1.8 per degree Celsius. The Mohs hardness of this soft metal measures 1.25. Its melting temperature sits intermediate between those of lighter strontium and heavier radium. The boiling point exceeds that of strontium despite being lower than radium. Density measures 3.62 grams per cubic centimeter which is again intermediate between strontium and radium. Because barium is difficult to purify many properties have not been accurately determined. Metallic barium reacts with atmospheric oxygen in air at room temperature so it is often stored under oil or in an inert atmosphere. Reactions with water and alcohols are exothermic and release hydrogen gas. Sulfuric acid stops reaction by forming insoluble barium sulfate on the surface through passivation.
Barium serves as a getter for vacuum tubes such as TV picture tubes to remove unwanted gases. This application gradually disappeared due to the popularity of tubeless LCD LED and plasma sets. Elemental barium acts as an additive to silumin aluminum-silicon alloys that refines their structure. Lead-tin soldering alloys use barium to increase creep resistance. An alloy with nickel creates spark plugs while additives to steel and cast iron act as inoculants. Barium combines with calcium manganese silicon and aluminium as high-grade steel deoxidizers. Barium sulfate functions as drilling fluid in oil and gas wells for the petroleum industry. The precipitate called blanc fixe from French permanent white appears in paints varnishes and plastics. It serves as filler in rubber paper coating pigment and nanoparticles to improve polymer physical properties. Baryte reserves estimate between 0.7 and 2 billion tonnes globally. Highest production reached 8.3 million tonnes in 1981 but only 7 to 8 percent went toward metal or compounds. China accounts for more than 50 percent of output followed by India at 14 percent in 2011. Morocco holds 8.3 percent US 8.2 percent Iran and Kazakhstan each hold 2.6 percent and Turkey 2.5 percent.
Barium sulfate first applied as radiocontrast agent in X-ray imaging of digestive system in 1908. This insoluble compound has low toxicity and relatively high density of approximately 4.5 grams per cubic centimeter. Its opacity to X-rays makes it useful for barium meals and barium enemas. Lithopone contains barium sulfate and zinc sulfide as a permanent white pigment that does not darken when exposed to sulfides. Soluble barium compounds have an oral lethal dose near 10 milligrams per kilogram for rats. Symptoms include convulsions paralysis of peripheral nerve system and severe inflammation of gastrointestinal tract. The insoluble sulfate is nontoxic and not classified as dangerous goods in transport regulations. Little is known about long term effects of barium exposure though US EPA considers unlikely carcinogenicity when consumed orally. Inhaled dust containing insoluble barium compounds can accumulate in lungs causing benign condition called baritosis. Barium carbonate used as rodenticide though considered obsolete may still be in use in some countries.
Global ocean circulation reveals strong correlation between dissolved barium and silicic acid. Large-scale ocean circulation combined with remineralization shows similar correlation between dissolved barium and ocean alkalinity. Particulate barium shows strong correlation with particulate organic carbon or POC. Barium becomes popular base for palaeoceanographic proxies to determine historical variations in biological pump carbon cycle and global climate. Barite in water column known as marine or pelagic barite reveals information on seawater chemistry variation over time. Barite in sediments known as diagenetic or cold seeps barite gives information about sedimentary redox processes. Hydrothermal barite formed via hydrothermal activity at vents reveals alterations in earth crust conditions around those vents. Lateral mixing caused by water mass mixing and ocean circulation affects distribution patterns. There is little depletion of barium concentrations in upper ocean for ion with nutrient-like profile thus lateral mixing important. Barium isotopic values show basin-scale balances instead of local or short-term processes. Average oceanic concentration measures 109 nanomoles per kilogram with residence time of 10,000 years.
Barium found in Earth's crust mixture includes seven primordial nuclides: barium-130 132 and 134 through 138. Barium-130 undergoes very slow radioactive decay to xenon-130 by double beta plus decay with half-life between 0.5 and 2.7 times ten to the twenty-first power years. This duration equals about one hundred billion times age of universe. Its abundance measures approximately 0.11 percent that of natural barium. Though barium-132 can theoretically undergo same decay giving xenon-132 experimental evidence has not detected this event. Stable isotope barium-138 composes 71.7 percent of all barium. Other isotopes have decreasing abundance with decreasing mass number except probable inversion for p-nuclei 130Ba and 132Ba. Total known isotopes range from 114 to 154 in mass. Most stable artificial radioisotope is barium-133 with half-life of 10.538 years. Five other isotopes have half-lives longer than a day. Longest-lived isomers include 133mBa at 38.90 hours and 135m1Ba at 28.11 hours. Analogous 137m1Ba with half-life 2.552 minutes occurs in decay of common fission product caesium-137.
Continue Browsing
Common questions
When was metallic barium first isolated by Sir Humphry Davy?
Sir Humphry Davy first isolated metallic barium in 1808. He achieved this isolation through the electrolysis of molten barium salts in England.
What are the primary industrial uses of barium sulfate today?
Barium sulfate functions as drilling fluid in oil and gas wells for the petroleum industry. It also serves as a radiocontrast agent in X-ray imaging of the digestive system since 1908.
How much global baryte production occurred in 1981?
Highest production reached 8.3 million tonnes in 1981. Only 7 to 8 percent of that output went toward metal or compounds at that time.
Which stable isotope composes the majority of natural barium?
Stable isotope barium-138 composes 71.7 percent of all barium. This isotope represents the largest abundance among all known isotopes ranging from 114 to 154 in mass.
Why does metallic baria oxidize rapidly upon exposure to air?
Metallic barium reacts with atmospheric oxygen in air at room temperature so it is often stored under oil or in an inert atmosphere. The silvery-white color vanishes rapidly upon oxidation yielding a dark gray layer containing the oxide.