Perchloric acid

Perchloric acid

Names
Systematic IUPAC name chloric(VII) acid
Other names Hyperchloric acid[1]
Identifiers
CAS Number	7601-90-3 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:29221 Y
ChEMBL	ChEMBL1161634 Y
ChemSpider	22669 Y
ECHA InfoCard	100.028.648
EC Number	231-512-4
PubChem CID	24247
RTECS number	SC7500000
UN number	1873
InChI InChI=1S/ClHO4/c2-1(3,4)5/h(H,2,3,4,5) Y Key: VLTRZXGMWDSKGL-UHFFFAOYSA-N Y InChI=1/ClHO4/c2-1(3,4)5/h(H,2,3,4,5) Key: VLTRZXGMWDSKGL-UHFFFAOYAD
SMILES O[Cl+3]([O-])([O-])[O-]
Properties
Chemical formula	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) (azeotrope)[4] −112 °C (anhydrous)
Boiling point	203 °C (397 °F; 476 K) (azeotrope)[2]
Solubility in water	miscible
Acidity (pKa)	−15.2 (±2.0);[3] ≈ −10
Conjugate base	Perchlorate
Hazards
Safety data sheet	ICSC 1006
GHS pictograms
GHS signal word	DANGER
GHS hazard statements	H271, H290, H302, H314, H373
GHS precautionary statements	P210, P280, P303+361+353, P304+340, P310, P305+351+338, P371, P380, P375
NFPA 704	0 3 3 OX
Flash point	Non-flammable
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).
Y verify (what is Y‹See TfM›N ?)
Infobox references

Perchloric acid is a mineral acid with the formula HClO₄. Usually found as an aqueous solution, this colorless compound is a stronger acid than sulfuric acid and nitric acid. It is a powerful oxidizer when hot, but aqueous solutions up to approximately 70% by weight at room temperature are generally safe, only showing strong acid features and no oxidizing properties. Perchloric acid is useful for preparing perchlorate salts, especially ammonium perchlorate, an important rocket fuel component. Perchloric acid is dangerously corrosive and readily forms potentially explosive mixtures.

Contents

• 
  1 Production
  
  
  
  • 
    1.1 Laboratory preparations
    
  
  
  
  


• 
  2 Properties
  


• 
  3 Uses
  
  
  
  • 
    3.1 As an acid
    
  
  
  
  


• 
  4 Safety
  


• 
  5 See also
  


• 
  6 References
  


• 
  7 External links
  

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.^[5][6]

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^[7] 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:^[8]

2 HClO₄ + P₄O₁₀ → Cl₂O₇ + "H₂P₄O₁₁"

Uses

Perchloric acid is mainly produced as a precursor to ammonium perchlorate, which is used in rocket fuel. The growth in rocketry has led to increased production of perchloric acid. Several million kilograms are produced annually.^[5] Perchloric acid is one of the most proven materials for etching of liquid crystal displays and critical electronics applications as well as ore extraction and has unique properties in analytical chemistry.^[9] Additionally it is a useful component in etching of chrome^[10]

As an acid

Perchloric acid, a superacid, is one of the strongest Brønsted–Lowry acids. Its pK_a is −10,^[11] −15.2 (±2.0).^[3] It provides strong acidity with minimal interference because perchlorate is weakly nucleophilic (explaining the high acidity of HClO₄). Other acids of 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.^[12] 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.^[13] It is highly reactive with metals (e.g., aluminium) and organic matter (wood, plastics). 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 when a bath, consisting of over 1000 litres of 75% perchloric acid and 25% acetic anhydride by volume, exploded. The O'Connor Electro-Plating plant, 25 other buildings, and 40 automobiles were obliterated, and 250 nearby homes were damaged. The bath was being used to electro-polish aluminium furniture. In addition, 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.^[14][15]

See also

• Chloric acid


• Oxidizing acid

References

1. 
   ^ Samuel Fomon. Medicine and the Allied Sciences. 1. p. 148..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""""'""'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
   


2. 
   ^ Handling of Perchloric acid^{[permanent dead link]}ameslab.gov
   


3. 
   ^ ^ab Trummal, A.; Lipping, L.; Kaljurand, I.; Koppel, I. A.; Leito, I. "Acidity of Strong Acids in Water and Dimethyl Sulfoxide" J. Phys. Chem. A. 2016, 120, 3663-3669. doi:10.1021/acs.jpca.6b02253.
   


4. 
   ^ Safety data for concentrated perchloric acid, ca. 70% msds.chem.ox.ac.uk
   


5. 
   ^ ^ab Helmut Vogt, Jan Balej, John E. Bennett, Peter Wintzer, Saeed Akbar Sheikh, Patrizio Gallone "Chlorine Oxides and Chlorine Oxygen Acids" in Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a06_483.
   


6. 
   ^ Müler, W.; Jönck, P. (1963). "Herstellung von Perchlorsäure durch anodische Oxydation von Chlor". Chemie Ingenieur Technik – CIT. 35 (2): 78. doi:10.1002/cite.330350203.; German patent DE1031288B; US patent US2846383A.
   


7. 
   ^ Almlöf, Jan; Lundgren, Jan O.; Olovsson, Ivar "Hydrogen Bond Studies. XLV. Crystal structure of perchloric acid 2.5 hydrate" Acta Crystallographica Section B: Structural Crystallography and Crystal Chemistry 1971, volume 27, pp. 898–904. doi:10.1107/S0567740871003236.
   


8. 
   ^ Holleman, Arnold F.; Wiberg, Egon (2001). Inorganic chemistry. Translated by Mary Eagleson, William Brewer. San Diego: Academic Press. p. 464. ISBN 0-12-352651-5.
   


9. 
   ^ "Perchloric Acid". GFS chemicals.
   


10. 
    ^ "Metal Etching". Thayer School of Engineering.
    


11. 
    ^ Kathleen Sellers; Katherine Weeks; William R. Alsop; Stephen R. Clough; Marilyn Hoyt; Barbara Pugh (2006). Perchlorate: environmental problems and solutions. CRC Press. p. 16. ISBN 0-8493-8081-2.
    


12. 
    ^ A. T. Balaban, C. D. Nenitzescu, K. Hafner and H. Kaiser (1973). "2,4,6-Trimethylpyrilium Perchlorate". Organic Syntheses.CS1 maint: Multiple names: authors list (link) ; Collective Volume, 5, p. 1106
    


13. 
    ^ Perchloric Acid, 60%, GR Material Safety Data Sheet Archived 2012-03-24 at the Wayback Machine. Seton Resource Center.
    


14. 
    ^ R. C. Nester; G. F. Vander Voort (1992). Safety in the Metallographic Laboratory. ASTM Standardization News. p. 34.
    


15. 
    ^ "CALIFORNIA: The Amazing Brew". Time.com. March 3, 1947.
    

External links

• International Chemical Safety Card 1006

v t e Hydrogen compounds

H3AsO3 H3AsO4 HAt HSO3F HBF4 HBr HBrO HBrO2 HBrO3 HBrO4 HCl HClO HClO2 HClO3 HClO4 HCN HCNO H2CrO4/H2Cr2O7 H2CO3 H2CS3 HF HFΟ HI HIO HIO2 HIO3 HIO4 HMnO4 H2MoO4 HNC NaHCO3 HNCO HNO HNO2 HNO3 H2N2O2 HNO5S H3NSO3 H2O H2O2 H2O3 H3PO2 H3PO3 H3PO4 H4P2O7 H5P3O10 H2PtCl6 H2S H2S2 H2Se H2SeO3 H2SeO4 H4SiO4 H2SiF6 HSCN HNSC H2SO3 H2SO4 H2SO5 H2S2O3 H2S2O6 H2S2O7 H2S2O8 CF3SO3H H2Te H2TeO3 H6TeO6 H4TiO4 H2Po HCo(CO)4

v t e Compounds containing perchlorate group
HClO4																	He
LiClO4	Be(ClO4)2											B(ClO 4)− 4 B(ClO4)3	ROClO3	N(ClO4)3 NH4ClO4 NOClO4	O	FClO4	Ne
NaClO4	Mg(ClO4)2											Al(ClO4)3	Si	P	S	ClO− 4 ClOClO3 Cl2O7	Ar
KClO4	Ca(ClO4)2	Sc(ClO4)3	Ti(ClO4)4	VO(ClO4)3 VO2(ClO4)	Cr(ClO4)3	Mn(ClO4)2	Fe(ClO4)3	Co(ClO4)2, Co(ClO4)3	Ni(ClO4)2	Cu(ClO4)2	Zn(ClO4)2	Ga(ClO4)3	Ge	As	Se	Br	Kr
RbClO4	Sr(ClO4)2	Y(ClO4)3	Zr(ClO4)4	Nb(ClO5)4	Mo	Tc	Ru	Rh(ClO4)3	Pd(ClO4)2	AgClO4	Cd(ClO4)2	In(ClO4)3	Sn(ClO4)4	Sb	TeO(ClO4)2	I	Xe
CsClO4	Ba(ClO4)2		Hf(ClO4)4	Ta(ClO5)5	W	Re	Os	Ir	Pt	Au	Hg2(ClO4)2, Hg(ClO4)2	Tl(ClO4)3	Pb(ClO4)2	Bi(ClO4)3	Po	At	Rn
FrClO4	Ra		Rf	Db	Sg	Bh	Hs	Mt	Ds	Rg	Cn	Nh	Fl	Mc	Lv	Ts	Og
		↓
		La	Ce(ClO4)x	Pr	Nd	Pm	Sm(ClO4)3	Eu(ClO4)3	Gd(ClO4)3	Tb(ClO4)3	Dy(ClO4)3	Ho(ClO4)3	Er(ClO4)3	Tm(ClO4)3	Yb(ClO4)3	Lu(ClO4)3
		Ac	Th(ClO4)4	Pa	UO2(ClO4)2	Np	Pu	Am	Cm	Bk	Cf	Es	Fm	Md	No	Lr

Authority control	GND: 4341998-7 LCCN: sh89001749 NDL: 00564389

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