Ammonium heptamolybdate

Last updated
Heptamolybdenan amonny.JPG
Names
IUPAC name
Ammonium docosaoxoheptamolybdate(6–)
Other names
Ammonium molybdate
Ammonium paramolybdate
(see text)
Identifiers
  • 12027-67-7 Yes check.svgY
  • 12054-85-2(tetrahydrate) Yes check.svgY
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.031.553 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 234-320-9
PubChem CID
UNII
  • InChI=1S/7Mo.6H3N.24H2O/h;;;;;;;6*1H3;24*1H2 Yes check.svgY
    Key: QGAVSDVURUSLQK-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/7Mo.6H3N.24H2O/h;;;;;;;6*1H3;24*1H2
    Key: QGAVSDVURUSLQK-UHFFFAOYAC
  • [NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[NH4+].[O-][Mo](=O)(=O)[O-].[O-][Mo](=O)(=O)[O-].[O-][Mo](=O)(=O)[O-]
  • [NH4+].[NH4+].[NH4+].[Mo]3479%12[O+]1[Mo]25([O-])([O-])O[Mo]1%10([O-])([O-])O[Mo]%11([O-])([O-])(O[Mo]8([O-])([O-])(O[Mo]6([O-])([O-])(O[Mo]([O-])([O-])(O2)(O3)[O++]456)[O+]78)[O++]9%10%11)O%12.[NH4+].[NH4+].[NH4+]
Properties
(NH4)6Mo7O24
Molar mass 1163.9 g/mol
1235.86 g/mol (tetrahydrate)
Appearancewhite solid
Density 2.498 g/cm3
Melting point ~90 ˚C (loses water molecule)
190 °C (decomp.)
65.3 g / 100 ml (tetrahydrate)
Hazards
Main hazards Irritant
Safety data sheet External MSDS
NFPA 704 (fire diamond)
2
0
0
Flash point Non-flammable
Related compounds
Other anions
Ammonium orthomolybdate
Ammonium dimolybdate
Other cations
Potassium paramolybdate
Related compounds
Molybdenum(VI) oxide
Molybdic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)
Infobox references

Ammonium heptamolybdate is the inorganic compound whose chemical formula is (NH4)6Mo7O24, normally encountered as the tetrahydrate. A dihydrate is also known. It is a colorless solid, often referred to as ammonium paramolybdate or simply as ammonium molybdate, although "ammonium molybdate" can also refer to ammonium orthomolybdate, (NH4)2MoO4, and several other compounds. It is one of the more common molybdenum compounds. [1]

Contents

Synthesis

Ammonium heptamolybdate is easily prepared by dissolving molybdenum trioxide in an excess of aqueous ammonia and evaporating the solution at room temperature. While the solution evaporates, the excess of ammonia escapes. This method results in the formation of six-sided transparent prisms of the tetrahydrate of ammonium heptamolybdate. [2]

Solutions of ammonium paramolybdate react with acids to form molybdic acid and an ammonium salt. The pH value of a concentrated solution will lie between 5 and 6.

Structure

The compound was first analyzed crystallographically by Lindqvist, but has been reanalyzed. [3] All Mo centers are octahedral. Some oxide ligands are terminal, some doubly bridging, and a few are triply bridging ligands.

The salt contains the heptamolybdate hexaanion. Mo7O246-.tif
The salt contains the heptamolybdate hexaanion.

Uses

Potassium heptamolybdate, also obtained as the tetrahydrate, is very similar to the ammonium salt. [3]

Safety

Molybdates are typically of low toxicity, so much so that few reports of incidents have ever been reported. [1]

Related Research Articles

An oxyanion, or oxoanion, is an ion with the generic formula A
x
Oz
y
. Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule. The corresponding oxyacid of an oxyanion is the compound H
z
A
x
O
y
. The structures of condensed oxyanions can be rationalized in terms of AOn polyhedral units with sharing of corners or edges between polyhedra. The oxyanions adenosine monophosphate (AMP), adenosine diphosphate (ADP) and adenosine triphosphate (ATP) are important in biology.

Ammonia solution, also known as ammonia water, ammonium hydroxide, ammoniacal liquor, ammonia liquor, aqua ammonia, aqueous ammonia, or (inaccurately) ammonia, is a solution of ammonia in water. It can be denoted by the symbols NH3(aq). Although the name ammonium hydroxide suggests an alkali with composition [NH4+][OH], it is actually impossible to isolate samples of NH4OH. The ions NH4+ and OH do not account for a significant fraction of the total amount of ammonia except in extremely dilute solutions.

Molybdenum trioxide is chemical compound with the formula MoO3. This compound is produced on the largest scale of any molybdenum compound. It is an intermediate in the production of molybdenum metal. It is also an important industrial catalyst. Molybdenum trioxide occurs as the rare mineral molybdite.

Molybdenum hexacarbonyl Chemical compound

Molybdenum hexacarbonyl (also called molybdenum carbonyl) is the chemical compound with the formula Mo(CO)6. This colorless solid, like its chromium and tungsten analogues, is noteworthy as a volatile, air-stable derivative of a metal in its zero oxidation state.

Molybdic acid Chemical compound

Molybdic acid refers to hydrated forms of molybdenum trioxide and related species. The monohydrate (MoO3·H2O) and the dihydrate (MoO3·2H2O) are well characterized. They are yellow diamagnetic solids.

Ammonium acetate, also known as spirit of Mindererus in aqueous solution, is a chemical compound with the formula NH4CH3CO2. It is a white, hygroscopic solid and can be derived from the reaction of ammonia and acetic acid. It is available commercially.

Uranyl acetate refers to the coordination polymer with the formula {[UO2(CH3CO2)2H2O)]H2O}n. In the polymer, uranyl (UO22+) centers are bridged by acetate ligands. The remainder of each (heptacoordinate) coordination sphere is provided by an aquo ligand and a bidentate acetate ligand. One water of crystallization occupies the lattice. It is a yellow-green solid.

In microscopy, negative staining is an established method, often used in diagnostic microscopy, for contrasting a thin specimen with an optically opaque fluid. In this technique, the background is stained, leaving the actual specimen untouched, and thus visible. This contrasts with positive staining, in which the actual specimen is stained.

Hexafluorosilicic acid Octahedric silicon compound

Hexafluorosilicic acid is an inorganic compound with the chemical formula H
2
SiF
6
also written as (H
3
O)
2
[SiF
6
]
. It is a colorless liquid mostly encountered as diluted aqueous solution, from there, the second chemical notation also proposed. Hexafluorosilicic acid has a distinctive sour taste and pungent smell. It is produced naturally on a large scale in volcanoes. It is manufactured as a coproduct in the production of phosphate fertilizers. The resulting hexafluorosilicic acid is almost exclusively consumed as a precursor to aluminum trifluoride and synthetic cryolite, which are used in aluminium processing. Salts derived from hexafluorosilicic acid are called hexafluorosilicates.

A solvated electron is a free electron in a solution, and is the smallest possible anion. Solvated electrons occur widely. Often, discussions of solvated electrons focus on their solutions in ammonia, which are stable for days, but solvated electrons also occur in water and other solvents – in fact, in any solvent that mediates outer-sphere electron transfer. The solvated electron is responsible for a great deal of radiation chemistry.

Biuret test

The biurettest, also known as Piotrowski's test, is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper(II) ion forms mauve-colored coordination complexes in an alkaline solution. Several variants on the test have been developed, such as the BCA test and the Modified Lowry test.

Ammonium tetrathiomolybdate Chemical compound

Ammonium tetrathiomolybdate is the chemical compound with the formula (NH4)2MoS4. This bright red ammonium salt is an important reagent in the chemistry of molybdenum and has been used as a building block in bioinorganic chemistry. The thiometallate anion has the distinctive property of undergoing oxidation at the sulfur centers concomitant with reduction of the metal from Mo(VI) to Mo(IV).

Molybdenum blue

Molybdenum blue is a term applied to:

Chloroauric acid Chemical compound

Chloroauric acid refers to inorganic compounds with the chemical formula HAuCl
4
·(H
2
O)
x
. Both the trihydrate and tetrahydrate are known. Both are orange-yellow solids consisting of the planar [AuCl4] anion. Often chloroauric acid is handled as a solution, such as those obtained by dissolution of gold in aqua regia. These solutions can be converted to other gold complexes or reduced to metallic gold or gold nanoparticles.

Ammonium molybdate can be of different form. These may be referred to :

Molybdate

In chemistry a molybdate is a compound containing an oxoanion with molybdenum in its highest oxidation state of 6. Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended structures, although the latter are only found in the solid state. The larger oxoanions are members of group of compounds termed polyoxometalates, and because they contain only one type of metal atom are often called isopolymetalates. The discrete molybdenum oxoanions range in size from the simplest MoO2−
4
, found in potassium molybdate up to extremely large structures found in isopoly-molybdenum blues that contain for example 154 Mo atoms. The behaviour of molybdenum is different from the other elements in group 6. Chromium only forms the chromates, CrO2−
4
, Cr
2
O2−
7
, Cr
3
O2−
10
and Cr
4
O2−
13
ions which are all based on tetrahedral chromium. Tungsten is similar to molybdenum and forms many tungstates containing 6 coordinate tungsten.

Ammonium orthomolybdate is the inorganic compound with the chemical formula (NH4)2MoO4. It is a white solid that is prepared by treating molybdenum trioxide with aqueous ammonia. Upon heating these solutions, ammonia is lost, to give ammonium heptamolybdate ((NH4)6Mo7O24.4H2O). Ammonium orthomolybdate is used as a corrosion inhibitor and is an intermediate in some schemes to win molybdenum from its ores.

Ammonium carbamate Chemical compound

Ammonium carbamate is an organic compound with the formula NH4[H2NCO2] consisting of ammonium NH+
4
and carbamate H
2
NCO
2
. It is a white solid that is extremely soluble in water, less so in alcohol. Ammonium carbamate can be formed by the reaction of ammonia with carbon dioxide, and will slowly decompose to those gases at ordinary temperatures and pressures. It is an intermediary in the industrial synthesis of urea, an important fertilizer.

Ammonium dimolybdate (ADM) is the inorganic compound with the formula (NH4)2Mo2O7. It is a white, water-soluble solid. ADM is an intermediate in the production of molybdenum compounds from its ores. Roasting typical ore produces crude molybdenum(VI) oxides, which can be extracted into aqueous ammonia, affording ammonium molybdate. Heating solutions of ammonium molybdate gives ADM. Upon heating, solid ammonium dimolybdate decomposes to molybdenum trioxide:

Cryogenic electron microscopy Form of transmission electron microscopy (TEM)

Cryogenic electron microscopy (cryo-EM) is a cryomicroscopy technique applied on samples cooled to cryogenic temperatures and embedded in an environment of vitreous water. An aqueous sample solution is applied to a grid-mesh and plunge-frozen in liquid ethane or a mixture of liquid ethane and propane. While development of the technique began in the 1970s, recent advances in detector technology and software algorithms have allowed for the determination of biomolecular structures at near-atomic resolution. This has attracted wide attention to the approach as an alternative to X-ray crystallography or NMR spectroscopy for macromolecular structure determination without the need for crystallization.

References

  1. 1 2 Sebenik, Roger F.; et al. (2000). "Molybdenum and Molybdenum Compounds". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.
  2. L. Svanberg & H. Struve, J. pr. Ch.44 [1848], p. 282; cited in Gmelin's Handbuch für Anorganische Chemie, 53, p. 255.
  3. 1 2 Evans, H.T., Jr.; Gatehouse, B. M.; Leverett, P. "Crystal Structure of the Heptamolybdate(VI) (paramolybdate) ion, (Mo7O24)6−, in the ammonium and potassium tetrahydrate salts" Journal of the Chemical Society. Dalton Transactions, Inorganic Chemistry1975, p.505-p514.
  4. Parsons, T.; Maita, V. & Lalli, C. (1984). A manual of chemical and biological methods for seawater analysis. Oxford: Pergamon.
  5. Harris, J. R. and Horne, R. W. 1991. "Negative staining", in Harris J. R. (Ed.), Electron Microscopy in Biology, Oxford University Press, Oxford.
  6. Adrian, Marc; Dubochet, Jacques; Fuller, Stephen D.; Harris, J. Robin (1998). "Cryo-negative staining". Micron. 29 (2–3): 145–160. doi:10.1016/S0968-4328(97)00068-1. PMID   9684350.
  7. De Carlo, S.; El-Bez, C.; Alvarez-Rúa, C.; Borge, J.; Dubochet, J. (2002). "Cryo-negative staining reduces electron-beam sensitivity of vitrified biological particles". Journal of Structural Biology. 138 (3): 216–226. doi:10.1016/S1047-8477(02)00035-7. PMID   12217660.

See also

Phosphate test aka Deniges' method links to here.