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CHEMINFO Record Number: 638
CCOHS Chemical Name: Potassium acid oxalate

Ethanedioic acid, monopotassium salt
Monopotassium ethanedioate
Monopotassium oxalate
Oxalic acid, monopotassium salt
Potassium hydrogen oxalate
Potassium binoxalate
Potassium oxalate
Potassium salt of sorrel
Sorrel salt
Ethanedioic acid, monopotassium salt, monohydrate
Potassium acid oxalate monohydrate

Chemical Name French: Binoxalate de potassium
CAS Registry Number: 127-95-7
Other CAS Registry Number(s): 6487-48-5
RTECS Number(s): RO3600000
Chemical Family: Saturated aliphatic carboxylic acid salt / saturated aliphatic dicarboxylic acid salt / alkanedioic acid / oxalate / monopotassium salt
Molecular Formula: C2-H-K-O4
Structural Formula: HO-CO-CO-O.K


Appearance and Odour:
Odourless, white crystals; hygroscopic (absorbs moisture from the air).(2)

Odour Threshold:

Warning Properties:
POOR - potassium acid oxalate is odourless.

Potassium acid oxalate is commercially available in a monohydrate crystalline form (CAS 6487-48-5). Potassium acid oxalate is one of the soluble salts of oxalic acid. It has many similarities (properties and hazards) to other oxalates. This record contains the available information specific for potassium acid oxalate, supplemented with general information on oxalic acid and oxalate salts which is applicable to potassium acid oxalate.

Uses and Occurrences:
Used in ink stain removal; cleaning metals and wood; in photography; mordant in dyeing; and bleaching agent for stearic acid.(2)



Effects of Short-Term (Acute) Exposure

Dust or mist (from solutions) can irritate the nose and throat, causing sore throat, coughing and difficult breathing.(4)

Skin Contact:
Dusts or mists (from solutions) may cause skin irritation, especially after prolonged exposure. No specific information is available, but excessive contact with the free acid, oxalic acid, may produce a delayed localized pain and discolouration of the skin, with fingernails becoming brittle and blue-coloured. These effects are attributed to the calcium-binding capability of oxalic acid and its salts.(4,5,9)
There is no specific information on the skin absorption of oxalate salts.

Eye Contact:
Dusts or mists (from solutions) can probably cause eye irritation. No specific information is available for eye contact, but oxalate salts have produced redness and swelling of mucous membranes.(8)

Oxalates can cause severe poisoning or death, depending on the concentration and total amount of material ingested. Dilute solutions may cause no immediate irritation or pain, while concentrated material (such as 10% solutions or the solid) can cause burning pain in the mouth, throat and stomach, followed by profuse, sometimes bloody, vomiting (corrosive effects).
Small doses of oxalate in the body may cause headache, cramps, pain, and twitching in muscles. Larger doses can cause weak and irregular heartbeat, a drop in blood pressure and signs of heart failure.(4)
Large doses rapidly cause a shock-like state, convulsions, coma and possibly death.(4,9)
The average lethal dose for an adult is probably about 10 to 15 grams but the lowest reported lethal dose was 1 gram (about 15 mg/kg).(1) A delayed effect of ingestion is kidney damage, possibly leading to kidney failure, due to deposition of calcium oxalate crystals.(4,5,9)

Effects of Long-Term (Chronic) Exposure

SKIN: Oxalate solutions can cause localized pain and discolouration of the fingers and nails, and possibly ulcers and gangrene.(9)
URINARY STONE FORMATION: No specific information is available for potassium acid oxalate. However, long-term exposure to oxalic acid by ingestion, skin absorption and inhalation has been linked to stone formation (calculi) in the kidney and urinary tract of workers. Painful abdominal spasms (during the passing of the stone), as well as painful and difficult urination were reported.(7)


Information not available

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:
Information not available

Reproductive Toxicity:
Information not available

Information not available

Toxicologically Synergistic Materials:
Information not available

Potential for Accumulation:
Potassium acid oxalate is excreted unchanged from the body or may be converted to crystals of calcium oxalate salt. This insoluble salt may be excreted or may accumulate in the body as stones (calculi) which can block the kidney or urinary tract.(3)


Remove source of contamination or move victim to fresh air. If breathing is difficult, obtain medical attention immediately.

Skin Contact:
Remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). As quickly as possible, flush contaminated area with lukewarm, gently running water for at least 10 minutes, by the clock. If irritation persists, obtain medical advice immediately. Completely decontaminate clothing, shoes and leather goods before re-use or discard.

Eye Contact:
Immediately flush the contaminated eye(s) with lukewarm, gently flowing water for 20 minutes, by the clock, holding the eyelid(s) open. Take care not to rinse contaminated water into the non-affected eye. If irritation persists, obtain medical attention immediately.

Never give anything by mouth if victim is rapidly losing consciousness, or is unconscious or convulsing. Have victim rinse mouth thoroughly with water. DO NOT INDUCE VOMITING. Have victim drink 240 to 300 mL (8 to 10 oz.) of water. If vomiting occurs naturally, rinse mouth and repeat administration of water. If breathing has stopped, trained personnel should begin artificial respiration or, if the heart has stopped, cardiopulmonary resuscitation (CPR) immediately. Transport victim to an emergency facility immediately. ADDITIONAL TREATMENT: Do not delay medical attention to give additional first aid, but the following procedure may be helpful if materials are readily available. If victim is conscious give immediately, by mouth, a few glasses of milk or a dilute solution of any soluble calcium salt: calcium lactate, lime water, finely pulverized chalk or plaster. Large amounts of calcium are required to inactivate oxalate by precipitating it as the insoluble calcium oxalate salt. DO NOT INDUCE VOMITING.(4)

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a physician and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a physician and appropriate delegation of authority obtained, as required.
All first aid procedures should be periodically reviewed by a physician familiar with the material and its conditions of use in the workplace.


Flash Point:
Not applicable (does not form vapour)

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:
Probably not sensitive. Stable material.

Sensitivity to Static Charge:
Insufficient information

Combustion and Thermal Decomposition Products:
Formic acid. Fumes may be highly toxic and irritating.

Extinguishing Media:
Use extinguishing media appropriate for the surrounding type of fire.

Fire Fighting Instructions:
Use water to keep fire-exposed containers cool. Water may be used to flush spills away from hazardous exposures.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 128.13 (anhydrous); 146.13 (monohydrate)

Conversion Factor:
Not applicable

Physical State: Solid
Melting Point: Decomposes when heated (6)
Boiling Point: Not applicable (does not form vapour)
Relative Density (Specific Gravity): 2.0 (water = 1) (6)
Solubility in Water: Moderately soluble (2.5 g/100 mL) (2,6)
Solubility in Other Liquids: Insoluble in alcohol and ether.(6)
Coefficient of Oil/Water Distribution (Partition Coefficient): Not available
pH Value: 2.7 (0.1 M solution) (2)
Vapour Density: Not applicable
Vapour Pressure: Not applicable
Saturation Vapour Concentration: Not applicable
Evaporation Rate: Not applicable


Normally stable unless heated.

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.

BASES - Vigorous reaction may occur, yielding heat and pressure.

STRONG OXIDIZING AGENTS - May react violently or explosively.

ALKALI METALS (e.g. sodium) - May react violently and produce flammable hydrogen gas.

Hazardous Decomposition Products:
Information not available

Corrosivity to Metals:
Information not available. Solutions are probably corrosive to metals.


No specific animal toxicity information available.


Selected Bibliography:
(1) Neugebauer, W. Acute lethal poisoning with potassium oxalate. Arch. Toxikologie. Vol. 19, no. 5 (1962). p. 275-277
(2) The Merck index: an encyclopedia of chemicals, drugs, and biologicals. 10th ed. Merck, 1983. p. 1098-1099
(3) Patty's industrial hygiene and toxicology. 3rd rev. ed. Vol. 2C. John Wiley & Sons, 1982. p. 4935-4939
(4) Gosselin, R.E., et al. Clinical toxicology of commercial products. 5th ed. Williams & Wilkins, 1984. p. II-198; III-326 - III-328
(5) Oxalic acid (Data sheet I-406-Rev. 86). National Safety Council, 1986
(6) CRC handbook of chemistry and physics. 64th ed. CRC Press, 1984. p. B-127
(7) Laerum, E., et al. Urolithiasis in railroad shopmen in relation to oxalic acid exposure at work. Scand. J. Work Environ. Health. Vol. 11, no. 2 (1985). p. 97-100
(8) Hajek, F. Oxalic acid and potassium oxalate intoxications. Casopsis Lekaru Ceskych. Vol. 68 (April 1929). p. 613-615
(9) Encyclopaedia of occupational health and safety. 3rd rev. ed. Vol. 2. ILO, 1983. p. 1574-1575
(10) European Economic Community. Commission Directive 93/72/EEC. September 1, 1993

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: 1990-01-19

Revision Indicators:
PEL-TWA 1993-03-01
Trans PEL-TWA 1993-04-01
TDG 1994-02-01
US Transport 1996-06-01
Protective equipment 1996-06-01
Resistance of materials 1996-06-01
EU number 1996-06-01
EU class 1996-06-01
EU risk 1996-06-01
EU safety 1996-06-01
EU comments 1996-06-01
Bibliography 1996-06-01
UN/NA No 2002-10-02
WHMIS detailed classification 2003-07-24
WHMIS health effects 2003-07-24

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