Sodium formate (CAS 141-53-7) is a single CAS number that reaches the market as two quite different products: a white crystalline powder sold at 92%, 95% or 98% minimum assay for leather, textile, oilfield and synthesis work, and a white irregular granule at 97% minimum, 2-6 mm and pH 8.0-11.0 sold as a chloride-free de-icing agent. The chemistry is identical – NaHCOO, molecular weight 68.01 – but the specification, the finishing step and the customer are not.
That split is worth understanding before a first purchase, because the two sheets are written by different people for different reasons and comparing them line by line without context leads to the wrong conclusion. This guide covers the chemistry, the two manufacturing routes, what each specification line actually controls, and how the granular de-icing grade differs from the chloride salts it competes with.
Current specifications for both grades are on the sodium formate product page.
1. The molecule
| Property | Value | Practical meaning |
|---|---|---|
| Chemical name | Sodium formate (sodium methanoate) | The sodium salt of the simplest carboxylic acid |
| Formula / MW | CHNaO2 / 68.01 | Sodium content 33.8%; formic acid equivalent 67.7% |
| Appearance | White crystalline powder or white irregular granules | Granules for spreader application, powder for solution and reaction use |
| Solubility | Very soluble – a saturated brine reaches roughly 1.33 g/cm3 density | The basis of solids-free, high-density drilling and completion fluids |
| pH in solution | Mildly alkaline, roughly 7-9 for the powder grade; the granular de-icing grade is specified at 8.0-11.0 | Alkalinity is a corrosion-control feature on steel and a caution on aluminium |
| Hygroscopicity | Hygroscopic | Drives bagging, storage and caking complaints |
| PubChem CID | 2723810 | Identity reference |
| Derived quantity | Calculation | Result |
|---|---|---|
| Formic acid equivalent | 46.03 / 68.01 | 67.7% – one kilogram of sodium formate carries the acid load of 0.68 kg formic acid |
| Sodium content | 22.99 / 68.01 | 33.8% – matters where sodium load is a constraint, as in some brines and in glass batch |
2. How sodium formate is made
Two routes dominate world supply, and which one your material came from explains most of the differences between 92%, 95% and 98% grades.
Route A – neutralisation of formic acid. Formic acid is neutralised with sodium hydroxide, and the solution is concentrated and crystallised:
HCOOH + NaOH -> NaHCOO + H2O
This route gives the highest purity with modest colour, and is the normal source of 98% material.
Route B – co-production from polyols. In the manufacture of pentaerythritol and neopentyl glycol, formaldehyde undergoes a crossed Cannizzaro reaction in the presence of alkali, and sodium formate is the stoichiometric by-product:
CH2O + HCHO + NaOH -> NaHCOO + CH3OH (simplified)
Sodium formate is recovered from the mother liquor by crystallisation. This is the largest single source of commercial sodium formate, and the reason 92% and 95% grades exist as legitimate products rather than as off-spec material: the recovery crystal carries more colour, more organic carry-over and more moisture than neutralisation-grade material, and there are plenty of applications where that is irrelevant.
A buyer who needs a colourless brine or a clean reaction medium should be buying 98% neutralisation-grade. A buyer deliming hides or reducing dye baths can take 92% and save the difference. Paying for 98% when 92% will do is the most common avoidable cost in this product.
3. The two specifications, side by side
| Parameter | Industrial powder 92 / 95 / 98% | Granular de-icing 97% | What it controls |
|---|---|---|---|
| Assay | Min 92%, 95% or 98% | Min 97% | Cost and colour. The de-icing grade sits high because 97% keeps the insoluble and organic load low enough to avoid residue on runways |
| Organic impurities | Max 2% | Not normally quoted | The industrial balance. High organic load shows as colour and COD in the liquor |
| Moisture | Max 2% | Quoted per batch | Caking. Above spec, a free-flowing powder becomes a block in the bag |
| Appearance | White crystalline powder | White irregular granules | A visual proxy for iron pickup and washing quality |
| Particle size | Powder, typically 40-100 mesh | 2-6 mm | The reason the granular grade exists at all |
| pH | Typically 7-9 in solution | 8.0-11.0 | Functional window for corrosion control (see section 6) |
Why the de-icing sheet leaves out impurities and adds pH and size
The industrial sheet is a chemistry document: it asks “how much sodium formate is in the bag and what else came along”. The de-icing sheet is an application document: it asks “will this material meter through a spreader, will it land where it is thrown, and what will it do to the steel and concrete underneath”. Organic impurities do not affect de-icing performance, so the sheet does not carry them. Particle size and pH do, so they are specified tightly.
Why particle size is the specification
Every de-icing applicator – a municipal spreader, a runway rig, a hand-held shaker – meters solids by volume and throws them through a spinner or drops them through an auger. Powder fluidises: it blows off the target area, dusts the operator, and drifts into drains rather than onto the ice. Granules in the 2-6 mm band fall where they are thrown, blend with rock salt without segregating, and survive storage in a silo without bridging.
The 2-6 mm band also matches the size of rock salt, which matters because most de-icing programmes use blends. Mismatched particle size is the most common cause of segregation in a blended de-icer: the fine fraction ends up at the bottom of the pile and the blend delivers the wrong ratio for the second half of the load.
Why 97% rather than 98% or 99%
Because de-icing does not need it. The residual 3% in the granular grade is largely moisture and a small alkaline reserve, and both are functionally acceptable on a road surface. Raising the assay would raise the cost without changing performance, which is why the de-icing grade is specified at 97% and not higher.
4. Industrial applications
| Sector | Function | Notes |
|---|---|---|
| Leather | Deliming, bating and chrome-tan masking | Buffers the pelt without the aggressiveness of a mineral acid; the formate ion also acts as a masking agent in chrome tanning |
| Textile dyeing and printing | Reducing agent and pH buffer | Used where a mild reductant is wanted without the sulphite load |
| Oilfield brines | Solids-free, high-density completion and drilling fluid | Saturated brine reaches about 1.33 g/cm3; chloride-free, which protects completion hardware |
| Chemical synthesis | Intermediate to formic acid, oxalic acid, sodium dithionite | Also a carbon source in some fermentations |
| Construction | Set accelerator and anti-freeze component in mortar and concrete | Milder than calcium formate, and it adds sodium rather than calcium to the mix |
| Flue gas and water treatment | Buffer and reducing agent | Also used in some SO2 scrubbing chemistry |
| Animal feed | Silage additive and acidifier component | Usually blended rather than used alone |
5. Sodium formate as a de-icing agent
The de-icing market is where sodium formate’s commercial story is clearest, because the competition is well defined and the failure modes of the incumbent are well documented.
What the product does on ice
Sodium formate dissolves into the meltwater film and depresses its freezing point, exactly as sodium chloride does. The difference is what happens afterwards: the formate ion is an organic anion that is readily biodegraded, and the material contains no chloride. That single fact decides where it is used.
Why airports and bridges buy it
Chloride de-icers attack the things around the road: reinforcing steel in bridge decks and ramps, galvanised guardrail and decking, the aluminium skins of aircraft, and the zinc coating on fasteners. They also mobilise heavy metals and add chloride to soils and watercourses. Sodium formate removes the chloride from the equation, and the alkaline reserve in the granular grade (pH 8.0-11.0) keeps steel in a pH range where its passive film is stable.
That combination is why formate-based de-icers are specified for runways, taxiways and aprons, for multi-storey car parks and ramps with post-tensioned steel, and for any site where run-off reaches a sensitive watercourse or a drinking-water catchment.
The honest trade-offs
Three points belong in any procurement discussion:
- Cost. Sodium formate costs several times what rock salt costs per tonne. It is bought for the damage it prevents, not for the melt.
- Oxygen demand. Biodegradability is not free. Sodium formate has a high biochemical oxygen demand, so large discharges into a small, slow watercourse can depress dissolved oxygen. The environmental case is “no chloride, no heavy metals, biodegradable” – not “no impact”.
- Alkalinity. A pH of 8.0-11.0 protects steel and attacks aluminium and zinc-rich coatings. Sites with aluminium cladding, aircraft skins or hot-dip galvanising need the dose and the grade checked against the material, not assumed.
How it compares with the chloride salts
| De-icer | CAS | Chloride | Corrosion to steel | Typical position in the market |
|---|---|---|---|---|
| Sodium chloride | 7647-14-5 | Yes | High – the reference case | Cheapest; highways and general roads |
| Calcium chloride | 10043-52-4 | Yes | High, and aggressive to galvanising | Fastest melt and exothermic; cold-weather boosting |
| Magnesium chloride hexahydrate | 7791-18-6 | Yes | High | Widely used liquid and treated-salt blends; lower cost than formates |
| Sodium formate | 141-53-7 | None | Low | Airports, bridges, car parks, sensitive catchments |
| Potassium acetate | 127-08-2 | None | Low | Runway de-icer; higher cost, strong oxygen demand |
| Urea | 57-13-6 | None | Low | Cheap non-chloride option, but a nitrogen load on water |
The chloride salts we hold are described on the magnesium chloride hexahydrate, calcium chloride 94% and calcium chloride 74% flakes pages. The chemistry behind the calcium chloride comparison is set out in our guide to calcium chloride applications by grade.
6. Safety, handling and storage
Sodium formate is a low-hazard solid. It is not flammable, not classified as a hazardous good for transport in normal packaging, and not a sensitiser. Dust irritates eyes and the respiratory tract; the alkaline granular grade is also mildly irritating to skin on prolonged contact, so gloves and goggles are appropriate at the bag dump and on the spreader.
Store under cover, sealed and dry, below 30 deg C. Both grades are hygroscopic. The granular grade tolerates an outdoor silo far better than the powder, but a silo that breathes humid air will bridge regardless of grade – fit a breather bag and keep the discharge cone warm in winter.
For de-icing tenders, have the corrosion data and the biodegradability test reports ready before the pre-qualification stage, not after. Tender documents usually ask for them as pass/fail items.
7. Buying guide
- Which grade by application, not by habit? 92% for deliming and reduction, 95% as a general workhorse, 98% for brines and clean reaction media, 97% granular for de-icing.
- Ask for the route. Neutralisation-grade and co-product-grade material behave differently in colour and moisture. If colour matters, specify the route.
- Granular means a size distribution, not a word. Ask for the percentage passing each sieve, plus the fines content below 2 mm.
- Check pH for de-icing. A granular lot at pH 8 and one at pH 11 are both “in spec” but behave differently on aluminium and on skin.
- Moisture and packaging. 25 kg PE-lined bags and 1000 kg jumbo bags are standard; bulk bags for de-icing contracts.
- Three consecutive COAs. Assay and moisture drift between lots is what produces caking complaints six months later.
8. FAQ
Is sodium formate the same as sodium methanoate?
Yes – both names describe CAS 141-53-7, NaHCOO.
What is the difference between the powder and the granular grade?
Assay is comparable (97% minimum for the granular grade), but the granular material is compacted or prilled to 2-6 mm and specified with a pH window of 8.0-11.0 so that it meters through a spreader and protects steel. The powder grade is sold on assay and moisture for solution and reaction use.
Is sodium formate a chloride-free de-icer?
Yes. It contains no chloride by formula, which is why it is specified where chloride run-off is unacceptable – airports, bridges, car parks and drinking-water catchments.
Why is the de-icing grade 97% and not 98%?
Because higher assay adds cost without adding performance on a road surface. The residual fraction is moisture and a small alkaline reserve, both acceptable in the application.
How much formic acid does sodium formate contain?
67.7% by weight, calculated as 46.03 / 68.01.
Can sodium formate be used in drilling fluids?
Yes – saturated sodium formate brine reaches about 1.33 g/cm3 and is used as a solids-free, chloride-free completion and drilling fluid.
References and further reading
- Formula, molecular weight and PubChem CID 2723810 – verified against the PubChem record for CAS 141-53-7.
- Formic acid equivalent and sodium content – calculated from atomic weights, working shown in section 1.
- Specification limits as quoted on the current product certificates for the industrial and granular grades.
- Related reading: calcium formate, magnesium chloride hexahydrate, calcium chloride applications by grade.
Disclaimer. This article is a technical and commercial overview for procurement and engineering readers. It does not replace the batch certificate of analysis, the safety data sheet, or the de-icing specification of a particular tender. Performance figures depend on concentration, temperature and the surface being treated.
For a current COA, the sieve analysis of the granular grade, or pricing on bagged and bulk-bag de-icing quantities, contact PolyBlueChem.
Related reading.