Summary. Fumaric acid and maleic acid have the same formula, C4H4O4, but are different isomers: fumaric is trans, maleic is cis. Maleic acid is the characteristic related impurity in fumaric acid, which is why our Food Grade specification limits it to 0.05 wt % maximum. Read the maleic acid line first, then assay on a dry basis, loss on drying and the heavy-metal limits, and check the CoA against the manufacturer's original. Technical grade is not food grade.
Are fumaric acid and maleic acid the same?
No. Both are C4H4O4, but they are geometric isomers: the two carboxylic acid groups sit on opposite sides of the carbon-carbon double bond in fumaric acid (trans) and on the same side in maleic acid (cis). That single difference changes physical properties and how each is used. Our product data describes fumaric acid as trans-butenedioic acid, the trans isomer of maleic acid, CAS 110-17-8. Maleic acid has its own CAS number, so the CAS on a quote, TDS or CoA is the check that separates them. The isomer descriptions in this section are general chemistry knowledge.
| Point | Fumaric acid | Maleic acid |
|---|---|---|
| Formula | C4H4O4 | C4H4O4 |
| Geometry | trans | cis |
| CAS number | 110-17-8 | Different; confirm on the document |
| Water solubility | 0.7 g/100 ml at 30 °C (SPC TDS) | Much more soluble (general knowledge) |
| Role in a food-grade fumaric acid CoA | The product | Controlled impurity, 0.05 wt % max on our TDS |
Why isomer purity shows up on the CoA
When two compounds share a formula, a simple assay can be misleading. An analysis that simply measures total acid content could not, on its own, tell the two isomers apart, because both are dicarboxylic acids of the same molecular weight. That is why a food-acid specification states an assay and also a separate limit for the related isomer. The assay tells you how much of the main component is present on a dry basis; the maleic acid line tells you how much of the cis form is allowed to accompany it. Reading only one of the two gives an incomplete picture. This explanation of why the lines are paired is general chemistry knowledge, not an SPC test method.
Why the maleic acid limit matters
When a specification states a maleic acid limit, it is telling you how much of the cis isomer is allowed in the trans product. Our Food Grade fumaric acid is specified at 0.05 wt % maximum maleic acid, per the manufacturer's Certificate of Analysis (FCC 14). A food formulator who wants a tight impurity profile should treat this line as seriously as the assay.
Do not confuse the product with a separate chemical family: maleic anhydride is a different product with its own page and its own specification. A material sold under a maleic name is not interchangeable with fumaric acid, and nothing in this guide describes maleic anhydride's grade or use.
Reading the CoA line by line
The table below takes each line of our fumaric acid specification and says what it tells you. The limits are from the manufacturer's CoA (FCC 14) summarised in TDS SPC-TDS-ACD-010; the "what it tells you" column is general knowledge.
| Parameter | Limit | What it tells you |
|---|---|---|
| Appearance | White crystalline powder | Basic identity and visible contamination check |
| Assay (dry basis) | 99.50 wt % min | Content of fumaric acid after allowing for moisture |
| Loss on drying | 0.25 wt % max | Moisture and volatile matter; links to the dry-basis assay |
| Maleic acid | 0.05 wt % max | Residual cis isomer |
| Infrared absorption | Conforms to reference standard | Identity test against a reference spectrum |
| Residue on ignition (sulfated ash) | 0.10 wt % max | Inorganic residue after burning |
| Colour (5% alcohol solution) | 20 APHA max | Colour-forming impurities |
| Arsenic (as As) | 1 ppm max | Toxic element limit |
| Heavy metals (as Pb) | 5 ppm max | Limit test for metals as a group |
| Lead (as Pb) | 2 ppm max | Specific toxic-metal limit |
| Solubility in water at 30 °C | 0.7 g/100 ml | Physical property, not a pass/fail limit; useful for planning dissolution |
A strong CoA and a weak CoA
Two documents can both claim "food grade" and still differ greatly in how much they prove. The comparison below is a checklist, not a statement about any particular supplier.
| Feature | Stronger CoA | Weaker CoA |
|---|---|---|
| Standard named | Names the compendium and edition (here, FCC 14) | Says only "food grade" |
| Batch identity | Batch number and date tied to the delivery | Undated, generic sheet |
| Results | Actual result against each limit, with units | Only a list of limits, or "complies" |
| Isomer purity | Separate maleic acid line | Assay only |
| Basis | Assay stated on a dry basis with loss on drying shown | Basis not stated |
| Source | Matches the manufacturer's original document | Retyped, with no link to the producer |
Check the CoA, not only the numbers
- Units and basis. Confirm the assay is stated on a dry basis and that wt % and ppm are used consistently.
- Standard and edition. Our figures cite FCC 14. Tell your supplier the edition your QA team needs and ask them to confirm it with the maker.
- Batch and date. A CoA must be tied to a batch number and date. A generic or undated sheet is not a batch record.
- Compare with the producer's original. Where possible, compare the CoA with the manufacturer's own document and check that every line, unit and limit matches, rather than trusting internal consistency alone.
- Maker's credentials. The FSSAI licence and REACH registration of Thirumalai Chemicals Limited are the manufacturer's credentials; they are not the supplier's.
Questions a buyer should ask any supplier
- Which standard and edition does the batch meet, and where does that appear on the CoA?
- Who is the manufacturer, and can the supplier show the producer's own CoA for the batch?
- Is the assay on a dry basis, and what is the loss on drying?
- What is the maleic acid result for this batch, not just the limit?
- What are the arsenic, heavy-metal and lead results?
- Which documents are supplied with each delivery, and which are not available?
Grade honesty
We list one grade: Food Grade to FCC 14. No technical, resin, feed or IP/BP/USP grade is listed. Technical grade is not food grade, and an E-number such as E297 identifies the substance rather than the quality of a batch. For the wider picture of food-grade standards, see our food-grade chemicals guide; to compare fumaric acid with other food acids, see food acidulants compared.
Documents and how to enquire
The TDS is SPC-TDS-ACD-010 (dated 2026-09-15), and a batch Certificate of Analysis is supplied with every delivery. A Safety Data Sheet is not yet published on the product page, so ask us what is available for your compliance file. Fumaric acid is packed in 25 kg bags. Fumaric acid price is by quotation; send quantity, delivery location and document needs, and we quote within 4 working hours. Call or WhatsApp +91 86087 80096.
Sources and basis
- Specification limits, grade, pack, maker and TDS number: SPC datasheet SPC-TDS-ACD-010 (scripts/tds-data/fumaric-acid.json), manufacturer's CoA against FCC 14.
- Chemical name and trans-isomer relationship: SPC product FAQ data for fumaric acid.
- Isomer geometry, relative solubility, the reasoning behind paired assay and impurity lines, and the CoA interpretation columns: general knowledge, not an SPC test method or specification.