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CHEMINFO Record Number: 639
CCOHS Chemical Name: Potassium oxalate

Ethanedioic acid, dipotassium salt
Dipotassium oxalate
Oxalic acid, dipotassium salt
Potassium oxalate monohydrate
Potassium oxalate, anhydrous
Anhydrous potassium oxalate

CAS Registry Number: 6487-48-5
Other CAS Registry Number(s): 583-52-8
RTECS Number(s): RO2885000
Chemical Family: Saturated aliphatic carboxylic acid salt / saturated aliphatic dicarboxylic acid salt / alkanedioic acid / oxalate / dipotassium salt
Molecular Formula: C2-K2-O4
Structural Formula: K.O-C(=O)-C(=)O-O.K


Appearance and Odour:
Colourless, odourless, transparent crystals (1,2); hygroscopic (absorbs moisture from the air) (8).

Odour Threshold:

Warning Properties:
POOR - potassium oxalate is odourless

Potassium oxalate can exist as the anhydrous compound (CAS 583-52-8) and as the monohydrate ((COOK)2.H2O) (CAS 6487-48-5). The monohydrate is industrially produced and is the normal commercial form. The anhydrous salt is obtained from the monohydrate.(9) Potassium oxalate is one of the soluble salts of oxalic acid. It has many similarities (properties and hazards) to other oxalates. This record contains the specific information available for potassium oxalate, supplemented with general information on oxalic acid and oxalate salts, which is applicable to potassium oxalate.

Uses and Occurrences:
Potassium oxalate is used in bleaching and cleaning; removing stains from textiles and in photography; as an in vitro blood anticoagulant; as a reagent in analytical chemistry; and as a source of oxalic acid.(1,2)


Colourless, odourless, transparent crystals. Hygroscopic. Does not form a vapour at room temperature, but can probably burn if heated to decomposition. May be harmful if swallowed. May cause kidney damage. Inhalation of dusts or mists can cause irritation of the nose, throat and upper respiratory tract. EYE IRRITANT. Causes severe eye irritation. May cause skin irritation.


Effects of Short-Term (Acute) Exposure

Potassium oxalate is a solid, which essentially does not form a vapour at room temperature. However, inhalation can occur following exposure to the dust or to mists or vapours formed from heated or misted solutions. In general, high concentrations of dusts or mists irritate the nose, and throat. There is no human or animal information available for potassium oxalate.

Skin Contact:
Potassium oxalate dust will absorb moisture from the skin and should be considered irritating. There is not enough information available to draw firm conclusions about the potential irritancy of potassium oxalate solutions. Therefore, these solutions should be considered irritating.
There is no specific information on the potential for skin absorption of oxalate salts.

Eye Contact:
Potassium oxalate should be considered a very severe eye irritant, based on animal information for sodium oxalate, a closely related oxalate. Permanent injury, including blindness, could result.

Potassium oxalate is expected to be toxic to humans if ingested, based on human case reports of poisoning (8,11-unconfirmed) and comparison to oxalic acid. The lowest published lethal dose for potassium oxalate is 1 gm/kg in a female.(8, unconfirmed) Potassium oxalate is expected to have essentially the same toxicity as oxalic acid if ingested.(4) There are numerous historical case reports of non-occupational poisoning with oxalic acid. Potassium oxalate may be irritating to the mouth, and throat and stomach. Absorbed oxalic acid causes calcium ion deficiency and symptoms such as headache, muscle cramps, and tetany (sharp flexion of the wrist and ankle joints, muscle twitching, cramps and convulsions) develop. The absorbed oxalic acid forms calcium oxalate, which is deposited in the kidneys, liver and other body tissues, and fatal kidney damage can develop. The single oral lethal dose for humans is estimated to be 50-500 mg/kg. The most commonly reported lethal oral dose for humans is 7-30 grams. Ingestion is not a typical route of occupational exposure.

Effects of Long-Term (Chronic) Exposure

There is no human information or reliable animal information available for potassium oxalate. Potassium oxalate has essentially the same toxicity as oxalic acid if ingested.(4) For other routes of exposure there is not enough information available to determine the potential toxicity of potassium oxalate as compared to oxalic acid. However, caution is advised since long-term occupational exposure to oxalic acid has been associated with harmful skin and kidney effects in humans.


There is no human or animal information 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:
There is no human or animal information available for potassium oxalate. Conclusions cannot be drawn based on the one limited study located for oxalic acid, a closely related chemical.

Reproductive Toxicity:
There is no human or animal information available for potassium oxalate. It is not possible to conclude that oxalic acid a closely related chemical, is a reproductive toxin. Oxalic acid caused reproductive toxicity in mice in one study, but the effects were observed in the presence of a significant reduction in water consumption in the parents of the first generation and increased kidney weight in the second generation.

There is no information available for potassium oxalate. The available information does not indicate that a closely related chemical, oxalic acid is mutagenic

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Potassium oxalate is readily metabolized to oxalic acid in the body. Oxalic acid is excreted in the urine at a rate of 8-40 mg/day in healthy normal men and women. About half is excreted as oxalic acid and half as magnesium, calcium or other salts. Ingested oxalic acid is also excreted in the feces. In rats, approximately half of ingested oxalic acid is destroyed by bacterial action and about 25% is excreted unchanged in the feces. In humans, calcium oxalate is deposited in the kidneys as crystals and may be deposited in non-crystalline form, bound to lipid, in the liver and other body tissues.


If symptoms are experienced, remove source of contamination or move victim to fresh air. Obtain medical advice.

Skin Contact:
As quickly as possible, remove contaminated clothing, shoes and leather goods (e.g. watchbands, belts). Immediately flush with lukewarm, gently flowing water for 15-20 minutes. If irritation persists, obtain medical attention 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 15-20 minutes, while holding the eyelid(s) open. If a contact lens is present, DO NOT delay irrigation or attempt to remove the lens. Take care not to rinse contaminated water into the unaffected eye or onto the face. Immediately obtain medical attention.

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. Immediately obtain medical attention.

First Aid Comments:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation or skin contact.
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 applicable. Does not form a 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.

Potential for Dust Explosions:
It is not known whether potassium oxalate can cause a dust explosion. Some potassium salts of carboxylic acids have caused dust explosions.

Combustion and Thermal Decomposition Products:
Carbon dioxide and carbon monoxide, potassium oxide, potassium carbonate, and other irritating and toxic fumes. Decomposes when heated to form potassium carbonate.(13)

Fire Hazard Summary:
Potassium oxalate does not form a vapour and is not combustible. However, it can probably burn if heated to decomposition.

Extinguishing Media:
Potassium oxalate does not burn. Use extinguishing media appropriate for the surrounding fire. Use water spray or fog to keep fire-exposed containers cool.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location. Approach fire from upwind to avoid toxic decomposition products.
Closed containers may rupture violently when exposed to the heat of the fire. If possible, isolate containers exposed to heat, but not directly involved in the fire. Move containers from the fire area if this can be done without risk. Protect personnel. Otherwise, use water in the form of spray or fog to keep fire-exposed containers cool and absorb heat to help prevent rupture, protect other fire-exposed material, prevent dust formation and to flush spills away from hazardous exposures. Solid streams of water may be ineffective and spread material. Water spray may also be used to knock down irritating/toxic combustion products which may be produced in a fire. Dike fire control water for appropriate disposal.

Protection of Fire Fighters:
Firefighters may enter the area if positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) and full Bunker Gear is worn.


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


Molecular Weight: 166.22 (anhydrous); 184.24 (monohydrate)

Conversion Factor:
Not applicable

Physical State: Solid
Melting Point: 160 deg C (320 deg F) (loses water to form anhydrous potassium oxalate) (9,13)
Boiling Point: Not applicable. Decomposes.(13)
Relative Density (Specific Gravity): 2.13 (water = 1) (13)
Solubility in Water: Slightly soluble (anhydrous) (19); Soluble (monohydrate) (25 g/100 mL at 20 deg C (9); 36 g/100 mL at 20 deg C (19))
Solubility in Other Liquids: Information not available.
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = -7.0 (estimated) (15)
pH Value: 7.0-8.5 (5% water solution at 20-25 deg C) (6)
Acidity: Practically neutral
Viscosity-Dynamic: Not applicable
Surface Tension: Not applicable
Vapour Density: Not applicable
Vapour Pressure: Zero (does not form a vapour).
Saturation Vapour Concentration: Not applicable
Evaporation Rate: Not applicable
Henry's Law Constant: Not available


Normally stable.

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.

STRONG OXIDIZING AGENTS (e.g. sodium chlorite or potassium permanganate) - may react violently or explosively.(8)

Hazardous Decomposition Products:
None reported.

Conditions to Avoid:
High temperatures. Generation of dust.

Corrosivity to Metals:
Potassium oxalate (saturated solution) is mildly corrosive (rate between 0.5 and 1.27 mm/year) to types 1010 and 1020 carbon steel.(16) Potassium oxalate (20% to saturated solution) is not corrosive to cast iron (unspecified), types 1075 and 1095 carbon steel, stainless steel (such as types 303, 304, 305, 316, 403, 410, 430, Carpenter 20Cb-3), type 3003 aluminum, copper, silicon bronze, bronze (unspecified), nickel, nickel base alloys, such as Hastelloy, Inconel, Incolloy and Monel, copper-nickel, tantalum, titanium and zirconium at 21 deg C.(10,16,17)

Corrosivity to Non-Metals:
Potassium oxalate (20%-saturated solution) does not attack plastics, such as epoxy, Teflon and other fluorocarbons, polyvinyl chloride (PVC), polyethylene, polypropylene, polysulfone and vinyl ester; and elastomers, such as fluorocarbons, Chemraz and Kalrez, at room temperature.(17,18)


No acute toxicity values were located.

Effects of Long-Term (Chronic) Exposure:

Rats were fed potassium oxalate at concentrations ranging from 0.06%-2.5% in their diets. Approximate doses were 12-680 mg/kg/day. Treated rats maintained for 10 weeks on a diet with optimal amounts of calcium, phosphorous and vitamin D showed no significant differences in growth rate or food consumption for any of the treatments. The only effect noted was a decrease in the ash content of the bones at 2.5%. According to the authors, this effect may indicate somewhat less efficient calcium (or phosphorus) utilization.(5) In a limited study, two dogs given sodium oxalate or potassium oxalate, twice a week, with total doses of 940 mg/kg (equivalent to 16 mg/kg/day) over 58 days and 2100 mg/kg (equivalent to 20 mg/kg/day) over 105 days, accumulated large quantities of oxalic acid in the kidney. Examination of cells from the organs of the dog dosed with 2100 mg/kg indicated kidney damage and deposits of large quantities of oxalate crystals.(3)


Selected Bibliography:
(1) Lewis, Sr., R.J., ed. Potassium oxalate. Hawley's condensed chemical dictionary. [CD-ROM]. 14th ed. John Wiley and Sons, Inc., 2002
(2) Potassium oxalate. The Merck index: an encyclopedia of chemicals, drugs and biologicals. Edited by M.J. O'Neil, et al. 13th ed. Merck and Company, 2001. p. 1371
(3) Heubner, W. Toxicity studies on dogs (oxalate). Archiv fuer Experimentelle Pathologie und Pharmakologie. Vol. 178 (1935). p. 749-754
(4) Gosselin, R.E., et al. Clinical toxicology of commercial products. 5th ed. Williams & Wilkins, 1984. p. II-198, III-326-III-328
(5) Mackenzie, C.G., et al. Some effects of dietary oxalate on the rat. The American Journal of Hygiene. Vol. 25, no. 1 (Jan. 1937). p. 1-10
(6) Fluka; Riedel-del-Haen. Potassium oxalate monohydrate. Laboratory chemicals and analytical reagents, 2001/2002. Sigma-Aldrich, 2001. p. 1205-1206
(7) National Institute for Occupational Safety and Health (NIOSH). Oxalic acid, dipotassium salt. Last updated: 97-09. In: Registry of Toxic Effects of Chemical Substances (RTECS(R)). [CD-ROM]. Canadian Centre for Occupational Health and Safety (CCOHS). Also available at: <>
(8) Potassium oxalate monohydrate. The Sigma-Aldrich library of chemical safety data. Ed. II. Vol. 2. Edited by R.E. Lenga. Sigma-Aldrich Corporation, 1988. p. 2907A
(9) Sawada, H., et al. Oxalic acid: derivatives: potassium oxalate. In: Kirk-Othmer encyclopedia of chemical technology. 4th ed. Vol. 17. John Wiley and Sons, 1996. p. 898
(10) Corrosion data survey: metals section. 6th ed. National Association of Corrosion Engineers, 1985. p. 102-8 to 103-8
(11) Hajek, F. Oxalic acid and potassium oxalate intoxications. Casopis Lekaru Ceskych. Vol. 68 (1929). p. 613-615
(12) European Economic Community. Commission Directive 93/72/EEC. Sept. 1, 1993
(13) Dean, J.A. Lange's handbook of chemistry. 15th ed. McGraw-Hill, Inc., 1999. p. 3.44
(14) Syracuse Research Corporation. The Physical Properties Database (PHYSPROP). Interactive PhysProp Database Demo. Date unknown. Available at: <>
(15) Syracuse Research Corporation. Interactive LogKow (KowWin) Database Demo. Date unknown. Available at: <>
(16) Pruett, K.M. Chemical resistance guide to metals and alloys: a guide to chemical resistance of metals and alloys. Compass Publications, 1995. p. 278-289
(17) 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. 2433-2436
(18) Pruett, K.M. Chemical resistance guide for plastics: a guide to chemical resistance of engineering thermoplastics, fluoroplastics, fibers and thermoset resins. Compass Publications, 2000. p. 422-433
(19) Lide, D.R., ed. Handbook of chemistry and physics. 82nd ed. CRC Press, 2001. p. 4-77 (potassium oxalate anhydrous and monohydrate)

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: 2005-08-25

Revision Indicators:
Bibliography 2006-01-17
Solubility in water 2006-01-17
Short-term eye contact 2006-01-25

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