Zinc bromide

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Zinc bromide
Zinc bromide
Zinc bromide
Identifiers
CAS number 7699-45-8 YesY
PubChem 24375
ChemSpider 22790 YesY
UNII OO7ZBU9703 YesY
RTECS number ZH1150000
Jmol-3D images Image 1
Properties
Molecular formula ZnBr2
Molar mass 225.198 g/mol
Appearance white crystalline powder
hygroscopic
Density 4.20 g/cm3 (20 °C)
4.22 g/cm3 (25 °C)
Melting point 394 °C
Boiling point 697 °C
Solubility in water 311 g/100 mL (0 °C)
447 g/100 mL (20 °C)[1]
538 g/100 mL (100 °C)[2]
Solubility very soluble in alcohol, ether, acetone, tetrahydrofuran
Refractive index (nD) 1.5452
Hazards
MSDS External MSDS
EU Index Not listed
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Non-flammable
Related compounds
Other anions Zinc fluoride,
Zinc chloride,
Zinc iodide
Other cations Cadmium bromide,
Mercury(II) bromide,
Calcium bromide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

Zinc bromide (ZnBr2) is an inorganic compound with the chemical formula ZnBr2. It is a colourless salt that shares many properties with zinc chloride (ZnCl2), namely a high solubility in water forming acidic solutions, and solubility in organic solvents. It is hygroscopic and forms a dihydrate ZnBr2 · 2H2O.

Production[edit]

ZnBr2 · 2H2O is prepared by treating zinc oxide or zinc metal with hydrobromic acid.

ZnO + 2 HBr + H2O → ZnBr2 · 2H2O

The anhydrous material can be produced by dehydration of the dihydrate with hot CO2 or by reaction of zinc metal and bromine.[3]

Structure[edit]

Crystalline ZnBr2 adopts the same structure as ZnI2: four tetrahedral Zn centers share three vertices to form “super-tetrahedra” of nominal composition {Zn4Br10}2-, which are linked by their vertices to form a three-dimensional structure.[4] The dihydrate ZnBr2 · 2H2O also has a usual structure and should be described as Zn(H2O)6 Zn2Br6, where the Zn2Br62− ion has bromine bridges linking the two zinc atoms. A similar structure is found in the dimeric form of aluminium bromide (Al2Br6).[5]

Gaseous ZnBr2 is linear in accordance with VSEPR theory with a Zn-Br bond length of 221 pm.[6]

Uses[edit]

Zinc bromide is used in the following applications:[3]

  • In oil and natural gas wells, solutions containing zinc bromide are used to displacing drilling mud when transistioning from the drilling phase to the completion phase or in well workover operations. The extremely dense brine solution gives the fluid its weight of 20 pounds/gallon, which makes it especially useful in holding back flammable oil and gas particles in high pressure wells. However, the high acidity and osmilarity cause corrosion and handling problems. Crews must be issued slicker suits and rubber boots because the fluid is so dehydrating.[7]
  • Zinc bromide solutions can be used as a transparent shield against radiation. The space between two glass panes is filled with a strong aqueous solution of zinc bromide with a very high density, to be used as a window on a hot cell. This type of window has the advantage over lead glass in that it will not darken as a result of exposure to radiation. All glass will darken slowly over time due to radiation, however this is especially true in a hot cell, where exceptional levels of radiation are present. The advantage of an aqueous salt solution is that any radiation damage will last less than a millisecond, so the shield will undergo self-repair.[8]

Safety[edit]

Safety considerations are similar to those for zinc chloride, for which the toxic dose for humans is 3–5 g.[3]

See also[edit]

References[edit]

  1. ^ Patnaik, P. (2003). Handbook of Inorganic Chemicals. McGraw-Hill Professional. ISBN 0-07-049439-8. 
  2. ^ "Zinc Bromide". Chemicalland21. 
  3. ^ a b c Rohe, D. M.; Wolf, H. U. (2005). "Zinc Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a28_537. 
  4. ^ Chieh, C.; White, M. A. (1984). "Crystal structure of anhydrous zinc bromide". Zeitschrift für Kristallographie 166 (3-4): 189–197. doi:10.1524/zkri.1984.166.3-4.189. 
  5. ^ Duhlev, R.; Brown, I. D.; Faggiani, R. (1988). "Zinc bromide dihydrate ZnBr2 · 2H2O: a double-salt structure". Acta Crystallografica C 44 (10): 1696–1698. doi:10.1107/S0108270188006584. 
  6. ^ Wells A. F. (1984). Structural Inorganic Chemistry (5th ed.). Oxford Science Publications. ISBN 0-19-855370-6. 
  7. ^ "Zinc Bromide - drilling fluids". Oilfield Glossary. Schlumberger. 
  8. ^ Blaylock, D. P.; Abu-Jawdeh, E. (January 1999). "The Georgia Institute of Technology High-Dose Gamma Irradiation Facility". 32nd Annual Midyear Meeting - Creation and Future Legacy of Stockpile Stewardship Isotope Production, Applications, and Consumption. Poster Session (Albuquerqe, NM: Health Physics Society).