Ammonium Oxalate Monohydrate: Uses & Handling Guide

What is Ammonium Oxalate used for? Ammonium Oxalate Monohydrate (CAS 6009-70-7) is the ammonium salt of oxalic acid, best known in analytical chemistry as a precipitating agent for calcium, lead, fluoride, and rare earth metal ions — its oxalate anion forms insoluble complexes with these metals, which is the basis for both classic gravimetric analysis and modern complexation reactions. Allan Chemical stocks it in ACS reagent grade, monohydrate form, with a Certificate of Analysis and SDS included on every shipment.

What Ammonium Oxalate Monohydrate Is

Ammonium Oxalate is the diammonium salt of oxalic acid, with the anhydrous formula (NH4)2C2O4 (CAS 1113-38-8) and a monohydrate form, (NH4)2C2O4·H2O (CAS 6009-70-7), with a molecular weight of about 142.11 g/mol.^[1] The monohydrate is the more common commercial and laboratory form, and it’s the form Allan Chemical stocks. It’s a colorless to white crystalline solid, odorless, and moderately soluble in water.

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Why It’s Useful in Analytical Chemistry

The same chemistry that makes this compound something to handle carefully is what makes it useful on the bench: its oxalate ion binds strongly with calcium and several other metal cations to form insoluble oxalate salts. That reaction is the working basis for classic quantitative calcium determination — precipitate the calcium as calcium oxalate, then measure it — and the same principle extends to detecting lead, fluoride, and rare earth metals. It also functions as a buffering reagent and a general laboratory chelating agent in solution chemistry.

Handling and Safety Considerations

Oxalate compounds are more hazardous to handle than most of the salts in a typical lab reagent shelf, and it’s worth being direct about that rather than glossing over it. The mechanism is specific: oxalate binds calcium in the body the same way it binds calcium in a test tube, which is why oxalic acid and its salts are known to disturb calcium balance in tissue if ingested or absorbed in quantity.^[2] New Jersey’s Department of Health lists Ammonium Oxalate specifically as harmful if swallowed or absorbed through skin, an eye irritant, and a compound requiring NIOSH-approved respiratory protection at any detectable airborne concentration, with the kidney identified as a target organ for prolonged exposure.^[3] None of this makes it unmanageable — it makes standard lab PPE (gloves, eye protection, adequate ventilation, avoiding dust generation) and a current SDS non-negotiable rather than optional.

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Grade and Form Notes

What to Verify Before Sourcing It

• Monohydrate vs. anhydrous confirmation — the two forms have different molecular weights, which matters for any quantitative work calibrated to one or the other.
• Current SDS on file, and confirmation the material meets ACS reagent specifications if the application calls for it.
• Appropriate PPE guidance from the supplier — gloves, eye protection, and ventilation requirements given the compound’s oral and skin toxicity profile.

See our guide to choosing the right chemical grade for lab applications for how ACS grade compares to other compendial standards.

FAQs

What is Ammonium Oxalate used for in a laboratory?

Primarily as a precipitating and complexing agent for metal ions — especially calcium, lead, fluoride, and rare earth metals — in both classic gravimetric analysis and modern analytical chemistry.

Is Ammonium Oxalate dangerous to handle?

It’s classified as harmful if swallowed and an eye irritant, with the kidney as a target organ for prolonged exposure, because its oxalate ion disrupts calcium balance. Standard lab PPE and adequate ventilation address this in routine handling.

What’s the difference between the monohydrate and anhydrous forms?

The monohydrate (CAS 6009-70-7, the form Allan Chemical stocks) includes one water molecule of crystallization and has a molecular weight of about 142.11 g/mol; the anhydrous form (CAS 1113-38-8) does not, and has a molecular weight of about 124.10 g/mol.

How should Ammonium Oxalate be stored?

In a tightly sealed original container, in a cool, dry, well-ventilated location, away from incompatible materials, per the current SDS.

References

1. PubChem — Ammonium Oxalate Monohydrate, Compound CID 62600
2. OSHA — Oxalic Acid Sampling Method PV2115 (toxicity background)
3. New Jersey Department of Health — Ammonium Oxalate Hazardous Substance Fact Sheet

This article is for general information and is not regulatory, safety, or formulation advice. Always consult the current official regulations and qualified professionals for your specific application.