Chemical knowledge
What Is Barium
1997/07/02 Bmschem
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Element |
Serial Number：56 |
Symbol：Ba |
Name：barium |
Type: mental |
Atomic weight：137.327 |
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Atomic Structure |
Atomic Radius /Å: 2.78 |
Ionic Radius /Å: 1.35 |
Electron Configuration: 1s2 2s2p6 3s2p6d10 4s2p6d10 5s2p66s2 |
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Atomic Volume /cm3/mol: 39.24 |
Oxidation State: 2 |
Covalent Radius/Å: 1.98 |
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Physical Property |
Melting Point(℃): 729 |
Boiling Point (℃): 1898 |
Density (g/cc，300K): 3.59 |
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Specific Heat/J/gK : 0.204 |
Melting Heat /KJ/mol: 7.75 |
Vaporization Heat /KJ/mol : 142 |
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Electric Conductivity /106/cm : 0.03 |
Heat Conductivity Coefficient /W/cmK: 0.184 |
Condition：soft，heavy silver metal |
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Geological Data |
Sun(relative to H=1×1012): 123 |
In seawater/p.p.m.： |
Residence time /year：10 000 |
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Earth crust /p.p.m.: 500 |
The surface of the Atlantic: 4.7 × 10-3 |
The surface of the Pacific Ocean: 4.7 × 10-3 |
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Atmosphere/p.p.m.（volume）: |
Deep in the Atlantic: 9.3 × 10-3 |
Deep in the Pacific Ocean: 20.0 × 10-3 |
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Biological Data |
blood/mg dm-3 : 0.068 |
liver/p.p.m.: 0.04 - 1.2 |
daily intake/mg: 0.6 - 1.7 |
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bone/p.p.m.: 3 - 70 |
muscle/p.p.m.: 0.09 |
per capita(70Kg) total body volume/mg: 22 |
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Discovery Process |
In 1808, David from Britain using mercury as cathode, conducted electrolysis of electrolyte made from barites and made mercury evaporate then got the barium. |
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Description |
Silver-white metal with slight gloss and malleability. Density: 3.51g/cm3. Melting Point: 725℃. Boiling point: 1640℃. Valence: +2. Ionization energy: 5.212 eV. It has flexible chemical property, which can react with the majority of nonmetal and burns in high temperature and oxygen to form BaO2. It oxidizes easily and can react with water to form hydroxide and hydrogen. It is soluble in acids and forms salt. All of barium salts are poisonous except barium sulfate. |
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Source |
There are barites and witherites in nature. It can be made from the electrolysis of molten barium chloride in the presence of ammonium chloride. Because of its high reactivity, there is no pure barium in nature. Metal elements of barium should be in immersed in mineral oil to store. |
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Use |
It is used for making barium salt, alloy, fireworks and so on and act as good deoxidizer when refine copper. It is also used for sparking plug, vacuum tube, fireworks and fluorescent lamp. |
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Material |
Barium, strontium, calcium and magnesium all are part of alkaline earth and major elements in earth’s crust. While compare with calcium and magnesium, the contents of barium and strontium is less. Besides, their compounds are not practically widely used as calcium and magnesium compounds. Therefore, their compounds are known by people much later than calcium and magnesium compounds. David just made barium, strontium, calcium and magnesium separated from compounds by electrolysis.
Sulfide of alkaline earth can generate phosphorescence that is when they struck by light, they will go on shining for a period of time in the darkness. Because of this feature, barium compounds begin to be noticed by people. In 1602, Cassio Lauro, a shoe-making worker in Bologna city, Italy, roasted barite containing barium sulfate with combustible material and found that it shined in the darkness, which aroused the interests of scholars at that time. Later, this kind of stone was called as Polola stone that aroused the analytical and investigative interests of European chemists. Up to 1774, Scheler believed that these stones were made up of the combination of a sort of fresh soil (oxide) and vitriol. In 1776, he heated the nitrate of this fresh soil and got pure soil (oxide) called baryta which is coming from Greek “barys” (heavy).
In the process of contacting with barium compounds people realized that barium compounds were poisonous. Nowadays, barium carbonates are used as rat poison, while the poisonousness of barium chloride to people is same as mercury. But barium sulfate is non-toxic. It is insoluble in water, acid or alkali, so it can not generate poisonous barium ions. Besides, it has the capability of prevent radial getting through, so doctors will ask you to eat it that is eating barium meal when inspect your intestines and stomach having lesions or not by making use of X-ray. Barium sulfate has no smell and it will automatically eliminate from the body after eating.
There is a wide range of barium compounds. Barium chloride (BacL2), barium carbide (BaC2), barium hydroxide [Ba(OH)2], barium carbonate (BaCO3), barium sulfide (BaS) and so on are frequently used in industry. Among them barium sulfate and barium carbonate are insoluble in water. Barium compounds have been widely used. For example, barium sulfate is used for white pigment and contrast agent of stomach and intestine. Barium chloride is used for making other barium salts or steel quench. Barium carbonate is applied to ceramic, enamel and glass industry. A lot of barium salts can be used as analytical reagent. |
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