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CHEMINFO Record Number: 14
CCOHS Chemical Name: Perchloric acid solutions 72% and less

Hydronium perchlorate
Perchloric acid (non-specific name)
Perchloric acid solutions (non-specific name)

Chemical Name French: Acide perchlorique (solutions de 72% ou moins)
CAS Registry Number: 7601-90-3
Other CAS Registry Number(s): 60477-26-1 13445-00-6 34099-94-0 35468-32-7 41371-23-1
UN/NA Number(s): 1802 1873
RTECS Number(s): SC7500000
EU EINECS/ELINCS Number: 231-512-4
Chemical Family: Mineral acid / inorganic acid / halogen oxygen acid / halogen oxo acid / chlorine oxygen acid / chlorine oxo acid
Molecular Formula: Cl-H-O4
Structural Formula: H-O-Cl(=O)3


Appearance and Odour:
Colourless, oily, odourless liquid. Very hygroscopic (absorbs moisture from the air) (concentrated solutions).(1,2,3,4)

Odour Threshold:

Warning Properties:
Insufficient information available for evaluation.

Water solutions of perchloric acid are usually available in concentrations of 60-62% or 70-72% by weight. The azeotropic mixture (a mixture that behaves as a single substance) contains 72.5% perchloric acid. It can also be purchased as a 20% concentration.(1,5,6) Perchloric acid forms a series of hydrates, HClO4.nH2O where n = 1 (CAS 60477-26-1), 2 (CAS 13445-00-6), 2.5 (CAS 34099-94-0), 3 (CAS 35468-32-7) and 3.5 (CAS 41371-23-1).(1,5) This CHEMINFO review presents hazard information and control measures for water solutions of perchloric acid of a concentration of 72% and less. For information on perchloric acid solutions of greater than 72% , refer to the CHEMINFO review for these materials (perchloric acid solutions greater than 72%).

Uses and Occurrences:
Perchloric acid is used to determine the trace metals present in oxidizable substances; as a laboratory reagent; as an oxidizing agent; for the destruction of organic matter; as a dehydrating agent; as a starting material for the manufacture of pure ammonium perchlorate and in the production of high purity metal perchlorates; as a stable reaction medium in the thermocatalytic production of chlorine dioxide; as an acetylation catalyst for cellulose and glucose; in the preparation of cellulose fibres; for fluoride determination; as an ingredient of electrolytic bath in deposition of lead; and in the electropolishing of metals.(1,2,5)


Colourless, oily, odourless liquid. Concentrated acid is very hygroscopic (absorb moisture from the air). Will not burn. Concentrated acid can decompose at high temperatures forming corrosive gases such as chlorine, hydrogen chloride and chlorine dioxide. MILD to STRONG OXIDIZING AGENT, depending on concentration of the solution and temperature. Promotes combustion. Contact with combustible or flammable materials can cause fire or explosion. Can react violently or explosively with many organic and inorganic chemicals. Vapours or mists are severely irritating to the respiratory tract. CORROSIVE to the eyes and skin. May cause blindness, severe burns and permanent scarring.


Effects of Short-Term (Acute) Exposure

Perchloric acid does not readily form a vapour at room temperature. Therefore, inhalation exposure is unlikely to occur unless it is misted. Mists formed from solutions are probably severely irritating or corrosive to the nose, throat and lungs, based on the acidity of perchloric acid. A severe exposure may result in a potentially life-threatening accumulation of fluid in the lungs (pulmonary edema). Symptoms of pulmonary edema (pain in the chest and coughing) may be delayed up to 24 hours following exposure. If heated, perchloric acid forms corrosive gases (chlorine and chlorine dioxide).(5) Refer to the CHEMINFO reviews of chlorine and chlorine dioxide for additional information.
There is no specific human or animal information available for perchloric acid.

Skin Contact:
Solutions are corrosive to the skin, due to the acidity of perchloric acid. In general, depending on the concentration of the solution and the duration and degree of exposure, corrosive materials can cause severe burns, blistering and permanent scarring.
There is no specific human or animal information available.

Eye Contact:
Mists and splashes of solutions are corrosive to the eye, due to the acidity of perchloric acid. In general, depending on the concentration of the solution and the duration and degree of exposure, corrosive materials can cause permanent eye damage, including blindness.

Perchloric acid solutions are corrosive liquids and ingestion can cause severe irritation or corrosive injury to the mouth, throat and stomach. Death could result. Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

No human or animal information was located.


No human or animal information was located.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has no listing for this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
No human or animal information was located.

Reproductive Toxicity:
No human or animal information was located.

No information was located.

Toxicologically Synergistic Materials:
No information was located.

Potential for Accumulation:
Perchloric acid does not accumulate in the body. Perchlorate is probably readily absorbed from the gastrointestinal tract. Perchlorate appears in the urine 1-17 minutes after oral dosing, which indicates that it is not appreciably metabolized (broken down) by humans. All absorbed perchlorate is excreted unchanged in urine within 48-72 hours.(7)


Can release corrosive compounds like chlorine. Take proper precautions to ensure your own safety before attempting rescue (e.g. wear appropriate protective equipment, use the buddy system). Remove source of contamination or move victim to fresh air. If breathing is difficult, trained personnel should administer emergency oxygen. DO NOT allow victim to move about unnecessarily. Symptoms of pulmonary edema can be delayed up to 48 hours after exposure. Quickly transport victim to an emergency care facility.

Skin Contact:
Avoid direct contact. Wear chemical protective clothing, if necessary. As quickly as possible, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Immediately flush with lukewarm, gently flowing water for at least 30 minutes. DO NOT INTERRUPT FLUSHING. If necessary, and it can be done safely, continue flushing during transport to emergency care facility. Quickly transport victim to an emergency care facility. Double bag, seal, label and leave contaminated clothing, shoes and leather goods at the scene for safe disposal.

Eye Contact:
Avoid direct contact. Wear chemical protective gloves, if necessary. Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for at least 30 minutes, while holding the eyelid(s) open. If a contact lens is present, DO NOT delay irrigation or attempt to remove the lens. Neutral saline solution may be used as soon as it is available. DO NOT INTERRUPT FLUSHING. If necessary, continue flushing during transport to emergency care facility. Quickly transport victim to an emergency care facility.

NEVER give anything by mouth if victim is rapidly losing consciousness, is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 60 to 240 mL (2 to 8 oz) of water. If vomiting occurs naturally, have victim rinse mouth with water again. Quickly transport victim to an emergency care facility.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures.
Some first aid procedures recommended above require advanced first aid training. Protocols for undertaking advanced procedures must be developed in consultation with a doctor and routinely reviewed.
All first aid procedures should be periodically reviewed by a doctor familiar with the material and its conditions of use in the workplace.


Flash Point:
Not combustible (does not burn).

Lower Flammable (Explosive) Limit (LFL/LEL):
Not applicable

Upper Flammable (Explosive) Limit (UFL/UEL):
Not applicable

Autoignition (Ignition) Temperature:
Not applicable

Sensitivity to Mechanical Impact:
Stable to shock.(10,11)

Sensitivity to Static Charge:
Perchloric acid will not accumulate static charge. Since it does not burn, perchloric acid will not be ignited by a static discharge.

Electrical Conductivity:
4.083 X 10(11) pS/m at 25 deg C (anhydrous acid); higher for aqueous solutions (10)

Combustion and Thermal Decomposition Products:
Oxygen, chlorine, chlorine oxides (predominantly chlorine dioxide, with some chlorine trioxide and chlorine tetroxide), hydrogen chloride.(5,10,11)

Fire Hazard Summary:
Perchloric acid solutions do not burn. However, perchloric acid is an oxidizing agent and is a serious fire and explosion hazard. Dilute (below 50%) or cold (below 49 deg C) perchloric acid solutions have little or no oxidizing power. Concentrated solutions (50-72%) are moderate to powerful oxidizing agents.(1,5,10,11) Concentrated perchloric acid solutions decompose giving off large amounts of oxygen, which form an oxygen-rich atmosphere that promotes combustion.(1,3,5) Perchloric acid solutions can cause combustible materials such as wood, paper, cotton, wool, cloth, oils and grease to ignite spontaneously (10,11) and will support, accelerate and intensify the burning of combustible materials in a fire. Some substances that do not normally burn in air will ignite or explode upon contact with perchloric acid. Explosive decomposition may occur under fire conditions and closed containers may rupture violently due to rapid decomposition, if exposed to fire or excessive heat for a sufficient period of time. No part of a container should be subjected to a temperature higher than 49 deg C (120 deg F).(12) During a fire, corrosive chlorine and hydrogen chloride gases and dangerously reactive and corrosive chlorine dioxide will be formed.

Extinguishing Media:
Perchloric acid does not burn. Extinguish fire using extinguishing agent suitable for the surrounding fire and not contraindicated for use with perchloric acid. Perchloric acid is an oxidizer. Therefore, flooding quantities of water spray or fog should be used to fight fires involving perchloric acid.(5,13)

Extinguishing Media to be Avoided:
DO NOT use dry chemical fire extinguishing agents containing ammonium compounds (such as some A:B:C agents), since an explosive compound can be formed. DO NOT use carbon dioxide, dry chemical powder or other extinguishing agents that smother flames, since they are not effective in extinguishing fires involving oxidizers.(12)

Fire Fighting Instructions:
Extreme caution is required in a fire situation. Evacuate area and fight fire from a protected, explosion-resistant location or maximum possible distance. Approach fire from upwind to avoid hazardous decomposition products.
If possible, isolate materials not involved in the fire, if this can be done without risk, and protect personnel. If perchloric acid is not involved in the fire, move perchloric acid containers from the fire area only if they have not been exposed to heat. Use extreme caution since explosive decomposition can occur under fire conditions and heat may rupture containers. Otherwise, apply water from as far a distance as possible, in flooding quantities as a spray or fog to keep fire-exposed containers or equipment cool and absorb heat, until well after the fire is out.
Remove all flammable and combustible materials from the vicinity, especially oil and grease. Do not direct water directly on leak as this may cause leak to increase. Stay away from ends of tanks, but realize that flying material from ruptured tanks may travel in any direction. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tanks due to fire. In an advanced or massive fire, the area should be evacuated. Use unmanned hoseholders or monitor nozzles.
Tanks or drums should not be approached directly after they have been involved in a fire or heated by exposure, until they have been completely cooled down. Clean-up or salvage operations should not be attempted until the perchloric acid is cooled.

Protection of Fire Fighters:
The decomposition products of perchloric acid such as chlorine, chlorine dioxide and hydrogen chloride are skin and inhalation hazards and are extremely hazardous to health. Do not enter without wearing specialized protective equipment suitable for the situation. Firefighter's normal protective equipment (Bunker Gear) will not provide adequate protection. Chemical protective clothing (e.g. chemical splash suit and positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) may be necessary.


NFPA - Health: 3 - Short exposure could cause serious temporary or residual injury. (perchloric acid greater than 50% and less than 72%)
NFPA - Flammability: 0 - Will not burn under typical fire conditions. (perchloric acid greater than 50% and less than 72%)
NFPA - Instability: 3 - Capable of detonation or explosive decomposition or explosive reaction, but requires a strong initiating source or must be heated under confinement before initiation, or reacts explosively with water. (perchloric acid greater than 50% and less than 72%)
NFPA - Specific Hazards: Oxidizing material. (perchloric acid greater than 50% and less than 72%)


Molecular Weight: 100.47

Conversion Factor:
Not applicable.

Physical State: Liquid
Melting Point: FREEZING POINT: -112 deg C (-170 deg F) (100%) (2,5,15)
Boiling Point: 132.4 deg C (270.3 deg F) (50.7% solution); 162.3 deg C (324 deg F) (61.2%) (1)
Relative Density (Specific Gravity): 1.41 (50% solution); 1.53 (60%); 1.67 (70%) at 20 deg C (water = 1) (1,10,11)
Solubility in Water: Soluble in all proportions.(1)
Solubility in Other Liquids: Information not available.
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = -4.63 (estimated) (16)
pH Value: 1 (1% solution); 0.5 (10% solution) (calculated)
Acidity: Perchloric acid is the strongest simple acid.(5) The pKa is a very large negative value.(15)
Viscosity-Dynamic: 1.82 mPa.s (1.82 centipoises) (50%); 2.8 mPa.s (2.8 centipoises) (60%); 4.5 mPa.s (4.5 centipoises) (70%) at 20 deg C (10)
Viscosity-Kinematic: 1.296 mm2/s (1.296 centistokes) (50%); 1.84 mm2/s (1.84 centistokes) (60%); 2.694 mm2/s (2.694 centistokes) (70%) at 20 deg C (10)
Surface Tension: 69.02 mN/m (69.02 dynes/cm) (53.7%); 69.7 mN/m (69.7 dynes/cm ) (60.7%); 69.5 mN/m (69.5 dynes/cm) (70.4%) at 25 deg C (10,11)
Vapour Density: Not applicable.
Vapour Pressure: Very low.
Saturation Vapour Concentration: Negligible.
Evaporation Rate: Negligible (3)


Normally stable.

Oxidizing Properties:
The NFPA lists perchloric acid solutions (less than 50% by weight) as Class 1 oxidizers, perchloric acid solutions (more than 50% but less than 60%) as Class 2 oxidizers, and perchloric acid solutions (60-72% by weight) as Class 3 oxidizers. A Class 1 oxidizer is an oxidizer whose primary hazard is that it slightly increases the burning rate but does not cause spontaneous ignition when it comes in contact with combustible materials. A Class 2 oxidizer will cause a moderate increase in the burning rate or cause spontaneous ignition of combustible materials with which it comes in contact. A Class 3 oxidizer will cause a severe increase in the burning rate of combustible materials with which it comes in contact or that will undergo vigorous self-sustained decomposition due to contamination or exposure to heat.(12) Temperature also influences oxidizing strength. At 160 deg C and above, concentrated solutions are very powerful oxidizing agents.(4,5,10,11) Although 68-72% perchloric acid behaves as a strong acid, it becomes a powerful oxidizer at elevated temperatures (greater than 160 deg C) or when anhydrous. It will be fairly readily dehydrated to the anhydrous acid with contact with strong concentrated acids.

Hazardous Polymerization:
Does not occur.

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

COMBUSTIBLE MATERIALS (e.g. wood, cotton, wool, cloth, oils or grease) or CELLULOSE and DERIVATIVES (e.g. paper, wood fibres, sawdust) - contact with hot concentrated acid may cause ignition or a violent explosion. Many fires have been caused by the long-term contact of dilute acid with wood.(4,13,18)
DEHYDRATING AGENTS (e.g. sulfuric acid, phosphorus pentoxide, phosphoric acid) - can explode spontaneously.(3,13,18)
ACETIC ANHYDRIDE and ACETIC ACID - mixtures are sensitive to shock, heat and the introduction of organic contaminants. Vapours above the heated liquid are flammable.(4,13,18)
ALCOHOLS (e.g. ethanol or methanol), BASES (e.g. sodium or potassium hydroxide), FLUORINE, TRICHLOROETHYLENE, ACETONITRILE, DIMETHYL ETHER, PHOSPHINE, PYRIDINE or NITRIC ACID and ORGANIC MATTER (e.g. vegetable oil, milk, plant material) - can react violently or explosively.(3,13,18)
GLYCOLS (e.g. ethylene glycol), GLYCOL ETHERS (e.g. 2-ethoxyethanol), GLYCEROL, DIETHYL ETHER or KETONES - undergo violent decomposition in contact with 68-72% perchloric acid.(13,18)
ANTIMONY COMPOUNDS (TRIVALENT) or BISMUTH - form explosive mixtures when hot.(4 ,13,18)
STEEL - explosions have occurred when 72% perchloric acid came into contact with steel.(4,18)
HYDRIODIC ACID, SODIUM IODIDE or SULFINYL CHLORIDE - ignite spontaneously on contact.(13,18)
HYPOPHOSPHITES (e.g. sodium hypophosphite) or REDUCING AGENTS (e.g. charcoal or sodium phosphinate) - can explode violently upon heating (5,13)
ORGANIC SULFOXIDES (e.g. dimethyl sulfoxide or dibutyl sulfoxide) - lower members of the series of salts formed are unstable and explosive when dry.(13,18)
NITROGEN TRIIODIDE or NITROSOPHENOL - addition of concentrated acid causes explosion.(13)
ANILINE and FORMALDEHYDE - react to form explosively combustible condensed resin.(18)

Hazardous Decomposition Products:
No information is available for solutions of 72% or less.

Conditions to Avoid:
Heat, combustible materials, other contaminants, dehydrating agents.

Corrosivity to Metals:
Perchloric acid solutions (10-70%) are corrosive to most common metals, such as cast iron, carbon steel, copper, brass, naval bronze, aluminum, stainless steels (types 304/347, 316 and type 400 series), Inconel, Monel, lead and nickel and its alloys. They are not corrosive to Hastelloy C, high silicon iron, 20 Cb 3 stainless steel, columbium, tantalum, titanium and zirconium.(19,20,21)

Corrosivity to Non-Metals:
Perchloric acid solutions (10-70%) attack some plastics (such as Acrylonitrile-butadiene-styrene (ABS), Acetal copolymer, Noryl, Nylon, Phenolic, Polyesters (Bisphenol A, isophthalic and terephthalic), polychloroprene (above 21 deg C), PVC (above 21 deg C)), elastomers (neoprene (70%), nitrile Buna A, polymethyl methacrylate (70%), polyurethane and silicone rubbers) and some coatings.(19,20,22) They do not attack chlorinated polyether (Penton), Chemraz, Kalrez, Kynar, Teflon, Halar, Hypalon, Tefzel, polyethylene (below 65 deg C), polypropylene (below 93 deg C), polyvinylidene chloride (Saran) and Viton A.(19,20)


LD50 (oral, rat): 1100 mg/kg (concentration not specified) (8,9-unconfirmed)
LD50 (oral, dog): 400 mg/kg (concentration not specified) (8,9-unconfirmed)

Effects of Short-Term (Acute) Exposure:

Insufficient details are available to evaluate a report of effects on the thyroid, blood system, cardiovascular system, liver and kidney following ingestion of an unspecified concentration of perchloric acid.(9)


Selected Bibliography:
(1) Vogt, H., et al. Chlorine oxides and chlorine oxygen acids: perchloric acid and perchlorates. In: Ullmann's encyclopedia of industrial chemistry. 5th completely rev. ed. Vol. A 6. VCH Verlagsgesellschaft, 1986. p. 517-525
(2) HSDB database record for perchloric acid. Last revision date: 2000/09/12
(3) Perchloric acid. In: Chemical safety sheets - working safely with hazardous chemicals. Kluwer Academic Publishers, 1991. p. 680
(4) Furr, A.K. Perchloric acid. In: CRC handbook of laboratory safety. 4th ed. CRC Press, 1995.
(5) Mendiratta, S.K., et al. Perchloric acid and perchlorates. In: Kirk-Othmer encyclopedia of chemical technology. 4th ed. Vol. 18. John Wiley and Sons, 1996. p. 177-170
(6) Sigma-Aldrich Canada Ltd. Available at: < ges/Main?EditDocument-> {Password required}
(7) Von Burg, R. Toxicology update: perchlorates. Journal of Applied Toxicology. Vol. 17, no. 3 (1995). p. 237-241
(8) RTECS record for perchloric acid. Last updated: 1999/07
(9) Selivanova, L.N., et al. On the general toxic effect of perchloric acid. Gigiena Truda I Professional'nye Zabolevaniya. (Labor Hygiene and Occupational Diseases). Vol. 17, no. 8 (1973). p. 33-35
(10) Schumacher, J.C. (ed). Perchlorates: their properties, manufacture and uses. American Chemical Society Monograph 146. Reinhold Publishing Corporation, 1960
(11) Schilt, A.A Perchloric acid and perchlorates. G. Frederick Smith Chemical Company, 1979
(12) NFPA 430. Code for the storage of liquid and solid oxidizers. 1995 edition. National Protection Association, 1995. p. 430-1 to 430-16
(13) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 49; NFPA 491
(14) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(15) Cotton, F.A., et al. Advanced inorganic chemistry: a comprehensive text. 4th ed. John Wiley and Sons, 1980. p. 235-236, 242, 244-245
(16) On-line LogP (octanol/water partition coefficient) database, including experimental data (Interactive LogKow (KowWin)). Available at: <//>
(17) Occupational Safety and Health Administration (OSHA). Perchloric acid. In: OSHA Chemical Sampling Information. Revision Date: 01/15/1993. Available at: <>
(18) Urben, P.G., ed. Bretherick's reactive chemical hazards database. 6th ed. Version 3.0. Butterworth-Heinemann Ltd., 1999
(19) Graf, Jr., F.A. Safe handling of perchloric acid. Chemical Engineering Progress. Vol. 62, no. 10 (Oct. 1966). p. 109-114
(20) Schweitzer, P.A. Corrosion resistance tables: metals, nonmetals, coatings, mortars, plastics, elastomers and linings, and fabrics. 4th ed. Part C, P-Z . Marcel Dekker, Inc., 1995. p. 2141-2148
(21) Corrosion data survey: metals section. 6th ed. National Association of Corrosion Engineers, 1985. p. 94-10 to 95-10
(22) Corrosion data survey: nonmetals section. 5th ed. National Association of Corrosion Engineers, 1983. p. 249 (1-17), 250 (13-17)
(23) European Economic Community. Commission Directive 93/72/EEC. Sept. 1, 1993
(24) Industrial Hygiene Group, Safety and Health Division, Brookhaven National Laboratory. Perchloric acid sampling and analysis procedure. Standard Operating Procedure. Number: IH75200. Revision: SHSD Final Rev 0. Date: 2001-09-28. Available at: <>

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 2003-03-24

Revision Indicators:
Resistance of materials for PPE 2004-04-08
Bibliography 2004-04-08
US transport 2005-11-10
Chemical name 2005-11-21
pH 2006-01-05

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