Perchloric acid

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Perchloric acid
Perchloric acid Hydroxidotrioxidochlorine
Perchloric acid
Hydroxidotrioxidochlorine
Perchloric acid ydroxidotrioxidochlorine
Perchloric acid
ydroxidotrioxidochlorine
Names
Systematic IUPAC name
Perchloric acid
Other names
Hyperchloric acid[1]
Identifiers
3D model (
JSmol
)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard
 100.028.648 Edit this at Wikidata
EC Number
  • 231-512-4
RTECS number
  • SC7500000
UNII
UN number 1873
  • InChI=1S/ClHO4/c2-1(3,4)5/h(H,2,3,4,5) checkY
    Key: VLTRZXGMWDSKGL-UHFFFAOYSA-N checkY
  • InChI=1/ClHO4/c2-1(3,4)5/h(H,2,3,4,5)
    Key: VLTRZXGMWDSKGL-UHFFFAOYAD
  • O[Cl+3]([O-])([O-])[O-]
Properties
HClO4
Molar mass 100.46 g/mol
Appearance colorless liquid
Odor odorless
Density 1.768 g/cm3
Melting point −17 °C (1 °F; 256 K) (72% aqueous solution)[2]
−112 °C (anhydrous)
Boiling point 203 °C (397 °F; 476 K) (azeotrope)[2]
Miscible
Acidity (pKa) −15.2 (±2.0);[3] ≈ −10
Conjugate base
 Perchlorate
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Powerful oxidizer, highly corrosive
GHS labelling:
GHS03: Oxidizing GHS05: Corrosive GHS07: Exclamation mark GHS08: Health hazard
Danger
H271, H290, H302, H314, H373
P210, P280, P303+P361+P353, P304+P340, P305+P351+P338, P310, P371, P375, P380
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 3: Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated under confinement before initiation, reacts explosively with water, or will detonate if severely shocked. E.g. hydrogen peroxideSpecial hazard OX: Oxidizer. E.g. potassium perchlorate
3
0
3
OX
Flash point Non-flammable
Safety data sheet (SDS) ICSC 1006
Related compounds
Related compounds
 Hydrochloric acid
Hypochlorous acid
Chlorous acid
Chloric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Perchloric acid is a

rocket fuel component. Perchloric acid is dangerously corrosive and readily forms potentially explosive mixtures.[4]

History

Perchloric acid was first synthesized (together with

Friedrich von Stadion [de] and called "oxygenated chloric acid" in mid-1810s. French pharmacist Georges-Simon Serullas introduced the modern designation along with discovering its solid monohydrate (which he, however, mistook for an anhydride).[5]

Production

Perchloric acid is produced industrially by two routes. The traditional method exploits the high aqueous solubility of sodium perchlorate (209 g/100 ml of water at room temperature). Treatment of such solutions with hydrochloric acid gives perchloric acid, precipitating solid sodium chloride:

NaClO4 + HCl → NaCl + HClO4

The concentrated acid can be purified by distillation. The alternative route, which is more direct and avoids salts, entails anodic oxidation of aqueous chlorine at a platinum electrode.[6][7]

Laboratory preparations

Treatment of barium perchlorate with sulfuric acid precipitates barium sulfate, leaving perchloric acid. It can also be made by mixing nitric acid with ammonium perchlorate and boiling while adding hydrochloric acid. The reaction gives nitrous oxide and perchloric acid due to a concurrent reaction involving the ammonium ion and can be concentrated and purified significantly by boiling off the remaining nitric and hydrochloric acids.

Properties

Anhydrous perchloric acid is an unstable oily liquid at room temperature. It forms at least five hydrates, several of which have been characterized crystallographically. These solids consist of the perchlorate anion linked via hydrogen bonds to H2O and H3O+ centers.[8] An example is hydronium perchlorate. Perchloric acid forms an azeotrope with water, consisting of about 72.5% perchloric acid. This form of the acid is stable indefinitely and is commercially available. Such solutions are hygroscopic. Thus, if left open to the air, concentrated perchloric acid dilutes itself by absorbing water from the air.

Dehydration of perchloric acid gives the anhydride dichlorine heptoxide:[9]

2 HClO4 + P4O10 → Cl2O7 + H2P4O11

Uses

Perchloric acid is mainly produced as a precursor to

liquid crystal displays and critical electronics applications as well as ore extraction and has unique properties in analytical chemistry.[10] Additionally it is a useful component in etching of chrome.[11]

As an acid

Perchloric acid, a

noncoordinating anions, such as fluoroboric acid and hexafluorophosphoric acid are susceptible to hydrolysis, whereas perchloric acid is not. Despite hazards associated with the explosiveness of its salts, the acid is often preferred in certain syntheses.[13] For similar reasons, it is a useful eluent
in ion-exchange chromatography.

It is also used for electropolishing or etching of aluminium, molybdenum, and other metals.

Safety

Given its strong oxidizing properties, perchloric acid is subject to extensive regulations as it can react violently with metals and flammable substances such as wood, plastics, and oils.[14] Work conducted with perchloric acid must be conducted in fume hoods with a wash-down capability to prevent accumulation of oxidisers in the ductwork.

On February 20, 1947 in Los Angeles, California, 17 people were killed and 150 injured in the O'Connor Plating Works disaster. A bath, consisting of over 1000 litres of 75% perchloric acid and 35% acetic anhydride by volume which was being used to electro-polish aluminium furniture, exploded. Organic compounds were added to the overheating bath when an iron rack was replaced with one coated with cellulose acetobutyrate (Tenit-2 plastic). A few minutes later the bath exploded.[15][16] The O'Connor Electro-Plating plant, 25 other buildings, and 40 automobiles were destroyed, and 250 nearby homes were damaged.

See also

References

  1. ^ Fomon, S. (1920). Medicine and the Allied Sciences. D. Appleton. p. 148.
  2. ^ a b "Safety (MSDS) data for perchloric acid, 70%". msds.chem.ox.ac.uk. 2 July 2008. Archived from the original on 2 July 2008. Retrieved 24 February 2022.
  3. ^
    S2CID 29697201
    .
  4. ^ "Perchloric Acid | Environmental Health & Safety | Michigan State University". ehs.msu.edu. Retrieved 2023-11-02.
  5. ^ Perchloric acid and perchlorates
  6. ^
    doi:10.1002/14356007.a06_483
    .
  7. doi:10.1002/cite.330350203.; German patent DE1031288B; US patent US2846383A
    .
  8. ISSN 0567-7408
    .
  9. ISBN 0-12-352651-5
    .
  10. ^ "Perchloric Acid". GFS chemicals. Archived from the original on 2015-01-31. Retrieved 2014-01-14.
  11. ^ "Metal Etching". Thayer School of Engineering.
  12. ISBN 0-8493-8081-2
    .
  13. ^ A. T. Balaban, C. D. Nenitzescu, K. Hafner and H. Kaiser (1973). "2,4,6-Trimethylpyrilium Perchlorate". Organic Syntheses{{cite journal}}: CS1 maint: multiple names: authors list (link); Collected Volumes, vol. 5, p. 1106.
  14. ^ "Materials Safety Data Sheet - Perchloric Acid, 60%, GR" (PDF). emd chemicals. 2003. Archived from the original (PDF) on 24 March 2012. Retrieved 24 February 2022.
  15. ^ R. C. Nester; G. F. Vander Voort (1992). Safety in the Metallographic Laboratory. ASTM Standardization News. p. 34.
  16. ^ "CALIFORNIA: The Amazing Brew". Time.com. March 3, 1947.

External links

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