Substance profile
Oxalic acid
Oxalic acid is an anhydrous oxalic acid, crystallized from glacial acetic acid is orthorhombic and is odorless.
01 · Identification
What Oxalic acid is
Oxalic acid is an anhydrous oxalic acid, crystallized from glacial acetic acid is orthorhombic and is odorless. Its molecular formula is C2H2O4 and its molecular weight is 90.03 g/mol. It melts at 190 °C.
Under the GHS it carries the signal word Warning. It is classed as corrosives.
02 · Identifiers
Oxalic acid identifiers and molecular data
Oxalic acid CAS number and EC number
Oxalic acid molecular formula and molecular weight
Other names for Oxalic acid
- C2H2O4
- Aktisal
- Aquisal
- Ethanedioic Acid
- Ethanedionic Acid
- Oxalic Acid (Aqueous)
- Oxalic Acid (As Dihydrate)
- Oxalic Acid Dihydrate
03 · GHS classification
Oxalic acid hazard classification
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
Oxalic acid pictograms and signal word
Oxalic acid hazard class and category
| Hazard class | Category | From code | Pictogram |
|---|---|---|---|
| Acute toxicity - oral GHS chapter 3.1 | Category 4 | H302 | GHS07 |
| Acute toxicity - dermal GHS chapter 3.1 | Category 4 | H312 | GHS07 |
Oxalic acid hazard statements (H-codes)
| Code | Hazard statement |
|---|---|
| H312 | Harmful in contact with skin. |
| H302 | Harmful if swallowed. |
This page lists only the codes assigned to Oxalic acid. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
Safety Data Sheet
Getting an SDS for Oxalic acid
Our own Oxalic acid safety data sheet walks through all sixteen sections of the published data. What it is not is the document an inspector asks for: an SDS is issued for a product by its supplier, so the sheet covering the grade actually standing in your store exists only in that supplier’s version. Collecting those and keeping them current as suppliers revise them is a separate job.
04 · Precautionary statements
Oxalic acid precautionary statements
CLP Annex VI assigns 7 precautionary statements to Oxalic acid. They are grouped the way a label groups them: what to do before handling, what to do when something has already happened, how to store it and how to dispose of it.
Prevention
What to do before and during handling so the hazard never happens.
Response
What to do once exposure, spillage or fire has already happened.
Reading the notation. … is a blank the supplier fills in — not a truncated sentence.· [square brackets] mark a part printed only when it applies.
05 · Names in the regulation
Oxalic acid name in 23 EU languages
CLP Annex VI Part 3 is published in every language edition of the regulation, and the identification column is written out in each of them. Nothing below is translated by us: each line is the name as that edition prints it. Under Art. 18(2) the substance name from Annex VI is a lawful product identifier, so this is the wording to put on a label going to that market — and where the cell lists several designations, any one of them qualifies.
| Language | Name in CLP Annex VI Part 3 |
|---|---|
| Bulgarian български | оксалова киселина |
| Spanish español | Ácido oxálico |
| Czech čeština | šťavelová kyselina |
| Danish dansk | oxalsyre |
| German Deutsch | Oxalsäure |
| Estonian eesti | oblikhape |
| Greek ελληνικά | οξαλικό οξύ |
| English English | oxalic acid |
| French français | acide oxalique |
| Croatian hrvatski | oksalna kiselina |
| Italian italiano | acido ossalico |
| Latvian latviešu | skābeņskābe |
| Lithuanian lietuvių | oksalo rūgštis |
| Hungarian magyar | oxálsav |
| Maltese Malti | aċidu ossaliku |
| Dutch Nederlands | oxaalzuur |
| Polish polski | kwas szczawiowy |
| Portuguese português | ácido oxálico |
| Romanian română | acid oxalic |
| Slovak slovenčina | kyselina šťaveľová |
| Slovenian slovenščina | oksalna kislina |
| Finnish suomi | oksaalihappo |
| Swedish svenska | oxalsyra |
All 23 language editions of Annex VI carry this entry. Irish is the twenty-fourth official EU language and has no line here for a different reason: no consolidated CLP text has ever been published in Irish, so there is no Irish edition of Annex VI to quote a name from. Source: consolidated CLP, CELEX 02008R1272, language editions. © European Union, https://eur-lex.europa.eu — only the electronic Official Journal of the European Union is authentic.
06 · Label elements
Oxalic acid GHS label elements
Everything CLP Annex VI fixes for Oxalic acid, laid out the way it appears on a label. The greyed lines are the parts only the supplier can fill in.
Warning
Oxalic acid
- Harmful in contact with skin.
- Harmful if swallowed.
- Do not eat, drink or smoke when using this product.
- Wear protective gloves/protective clothing/eye protection/face protection/hearing protection/…
- IF SWALLOWED:
- IF ON SKIN:
- Call a POISON CENTER/doctor/… if you feel unwell.
- Rinse mouth.
- Wash with plenty of water/…
Supplier name, address and telephone number· Product identifier·Nominal quantity
Need this as an actual label? Open Oxalic acid in the GHS label constructor →
07 · Health hazards
Oxalic acid health hazards and exposure limits
Oxalic acid occupational exposure limits
| Limit | Value | Source |
|---|---|---|
| PEL | 1.0 [mg/m3] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| PEL | 1 mg/m³ | Occupational Safety and Health Administration (OSHA) |
| PEL | TWA 1 mg/m3 See Appendix G | The National Institute for Occupational Safety and Health (NIOSH) |
| REL | 1 mg/m³ | Occupational Safety and Health Administration (OSHA) |
| REL | 2 mg/m³ | Occupational Safety and Health Administration (OSHA) |
| REL | TWA 1 mg/m3 ST 2 mg/m3 | The National Institute for Occupational Safety and Health (NIOSH) |
| IDLH | 500 mg/m3 (NIOSH, 2024) | CAMEO Chemicals |
| IDLH | 500.0 [mg/m3] | Haz-Map, Information on Hazardous Chemicals and Occupational Diseases |
| IDLH | 500 mg/cu m | Hazardous Substances Data Bank (HSDB) |
These are United States values. The European Union sets its own indicative and binding limits, and the figure that applies at a given workplace is the one in the local regulation — not the one shown here.
08 · Physical and chemical properties
Oxalic acid properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
Oxalic acid boiling point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | Sublimes | sublimes | NIOSH |
| Sublimes (NIOSH, 2024) | sublimes | CAMEO | |
| sublimes | sublimes | OSHA |
Oxalic acid melting point
| Property | Value | Conditions | Source |
|---|---|---|---|
| Melting point | 189.5 °C (373.1 °F) | ICSC | |
| 188.89 °C (372 °F) | OSHA | ||
| 189.5 °C (373.1 °F) | decomposes, DECOMPOSES | HSDB |
Oxalic acid density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Density | 1.9 g/cm³ | HSDB |
Oxalic acid solubility
| Property | Value | Conditions | Source |
|---|---|---|---|
| Solubility | VERY SOL IN ETHANOL; SLIGHTLY SOL IN ETHER; INSOL IN BENZENE, CHLOROFORM, PETROLEUM ETHER | HSDB | |
| 14% | NIOSH | ||
| Water solubility of 220,000 mg/l at 25 °C | at 25 °C | HSDB |
Oxalic acid vapor pressure
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor pressure | 0.001 mmHg | at 20 °C | CAMEO |
| 0.001 mmHg | below this value | NIOSH |
Oxalic acid autoignition temperature
| Property | Value | Conditions | Source |
|---|---|---|---|
| Autoignition temperature | Not flammable (USCG, 1999) | CAMEO |
Oxalic acid lower explosive limit (LEL)
| Property | Value | Conditions | Source |
|---|---|---|---|
| Lower explosive limit (LEL) | Combustible Solid | NIOSH |
Oxalic acid vapor density
| Property | Value | Conditions | Source |
|---|---|---|---|
| Vapor density | 4.3 (air = 1) | CAMEO |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
09 · Handling and storage
Oxalic acid storage and handling
Oxalic acid reactive group
CAMEO Chemicals places Oxalic acid in the reactive group Acids, Carboxylic. Compatibility with other chemicals is worked out from the group, not from the individual substance — which is why two substances you have never seen react can still be flagged as a pair that must be separated.
A reactive group is a CAMEO Chemicals (US NOAA) grouping, not a GHS hazard class: it has no code, no category and no legal force. It is what the storage compatibility matrix on this site computes from.
Oxalic acid safe storage
Separated from strong oxidants and food and feedstuffs. Dry. Well closed.
Source: ILO-WHO International Chemical Safety Cards (ICSCs)
Oxalic acid storage conditions
STORE IN COOL, DRY, WELL-VENTILATED LOCATION. /OXALIC ACID DIHYDRATE/
Source: Hazardous Substances Data Bank (HSDB)
Oxalic acid incompatible materials
Reacts with strong alkalies, strong oxidizing materials, chlorites, and hypochlorites. /Oxalic acid dihydrate/
Source: Hazardous Substances Data Bank (HSDB)
Oxalic acid reactivity
OXALIC ACID is hygroscopic and sensitive to heat. This compound may react violently with furfuryl alcohol, silver, sodium, perchlorate, sodium hypochlorite, strong oxidizers, sodium chlorite, acid chlorides, metals and alkali metals. (NTP, 1992). The heating of mixtures of Oxalic acid and urea has lead to explosions. This is due to the rapid generation of the gases CO2, CO, and NH3 [Praxis Naturwiss. Chem., 1987, 36(8), 41-42]. Oxalic acid and urea react at high temperatures to form toxic and flammable ammonia and carbon monoxide gases, and inert CO2 gas [Von Bentzinger, R. et al., Praxis Naturwiss. Chem., 1987, 36(8), 41-42].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Oxalic acid in the storage compatibility matrix →
10 · Questions
Oxalic acid — frequently asked questions
What is the CAS number of Oxalic acid?
The CAS number of Oxalic acid is 144-62-7. Its EC number is 205-634-3.
What is the chemical formula of Oxalic acid?
The molecular formula of Oxalic acid is C2H2O4 and its molecular weight is 90.03 g/mol.
What does a Oxalic acid label have to show?
Under CLP Annex VI the label for Oxalic acid carries the pictogram Exclamation mark and the signal word is Warning.
Is Oxalic acid flammable?
CLP Annex VI assigns Oxalic acid no flammability hazard class. That is not a statement that it cannot burn: the harmonised list only records the hazards that were assessed for it.
Is Oxalic acid a carcinogen?
CLP Annex VI records no harmonised carcinogenicity classification for Oxalic acid. Annex VI is a list of agreed classifications, not a list of substances found safe, so this is an absence of a classification rather than a clean bill of health.
What is the exposure limit for Oxalic acid?
The US occupational exposure limit reported for Oxalic acid is 1.0 [mg/m3] (Haz-Map, Information on Hazardous Chemicals and Occupational Diseases). Limits differ by country: the EU sets its own indicative and binding values, and the figure that applies at a given workplace is the one in the local regulation.
What is the boiling point of Oxalic acid?
The boiling point reported for Oxalic acid is Sublimes, sublimes (NIOSH).
What is the melting point of Oxalic acid?
The melting point reported for Oxalic acid is 189.5 °C (373.1 °F) (ICSC).
How should Oxalic acid be stored?
STORE IN COOL, DRY, WELL-VENTILATED LOCATION. /OXALIC ACID DIHYDRATE/ (Hazardous Substances Data Bank (HSDB))
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