Start with the concentration your process actually needs
Sulfuric acid (H₂SO₄, CAS 7664-93-9) is sold across a wide concentration range, and the correct one is set by the chemistry of your process rather than by price per tonne. Buying stronger acid than you need means paying to ship water you will later add back, and handling a more aggressive material than the job requires. Buying weaker acid than the process demands can stall a reaction outright.
| Grade | Concentration | Typical use |
|---|---|---|
| Dilute | 10–35% | pH correction, dilute process steps, effluent neutralisation |
| Battery / electrolyte | 29–32% | Lead-acid battery filling and manufacture |
| Tower or chamber acid | 60–70% | Some fertiliser routes, ore leaching |
| Technical | 93% | Fertiliser production, metal pickling, detergent manufacture |
| Concentrated | 98% | Chemical synthesis, dehydration reactions, alkylation |
| Oleum (fuming) | 20–65% free SO₃ | Sulphonation and specialty synthesis; tightly controlled |
For most Pakistani industrial buyers the decision comes down to 98% concentrated or 93% technical. The 93–98% band carries the large majority of industrial demand because it balances reactivity against handling practicality. If your process adds water immediately after dosing, specify 93% and save on freight.
What the specification should say beyond the assay
Concentration tells you how much acid is in the drum. It says nothing about what else is. For most industrial applications these are the parameters worth naming on the purchase order.
- Assay (% H₂SO₄ w/w) — with a stated tolerance, not a bare number
- Iron (Fe) — the parameter that most often causes rejection; matters in textile, battery and any application where staining or catalyst poisoning is a risk
- Chloride — drives pitting corrosion of stainless steel handling equipment even at low concentrations
- Colour — a yellow or brown cast usually indicates organic contamination or iron pickup from storage
- Residue on ignition / non-volatile matter — indicates dissolved solids carried over from production
- Arsenic and heavy metals — required where the acid touches food, pharmaceutical or feed chains
Battery-grade acid is the strictest of the common grades. Lead-acid cells are poisoned by iron, chloride and organic matter, so electrolyte acid is specified against tighter limits than technical acid at the same concentration. Never substitute technical 93% diluted down for battery grade.
Key physical properties
| Property | Value |
|---|---|
| Chemical formula | H₂SO₄ |
| CAS number | 7664-93-9 |
| Molecular weight | 98.08 g/mol |
| Appearance | Colourless to slightly yellow, oily liquid |
| Density (98%) | 1.84 g/cm³ |
| Density (93%) | 1.83 g/cm³ |
| Boiling point (98%) | 337 °C |
| Melting point (98%) | 10.3 °C |
| Miscibility | Fully miscible with water; strongly exothermic |
| UN number | 1830 concentrated · 1832 spent · 2796 battery acid |
| Hazard class | 8 — Corrosive |
The melting point matters more than buyers expect. Concentrated 98% acid solidifies at about 10 °C, which is reachable on winter nights in Lahore, Faisalabad and further north. Storage that is fine in July can freeze a line in January.
Materials of construction and storage
Sulfuric acid is unusual in that its corrosivity is not proportional to concentration. Concentrated acid above roughly 93% passivates carbon steel by forming a protective iron sulphate film, which is why bulk concentrated acid is routinely stored in mild steel tanks. Dilute acid destroys that same steel rapidly.
- Above ~93% — carbon steel is acceptable for storage at ambient temperature and low flow velocity
- Below ~70% — carbon steel is not suitable; use HDPE, PTFE-lined steel, or suitable alloys
- Any concentration at elevated temperature or high velocity — treat steel as unsuitable and specify lined or alloy equipment
- Never use galvanised, aluminium or copper alloys in any sulfuric acid service
Dilution is the single most dangerous routine operation. Diluting concentrated acid releases enough heat to boil water locally. Always add acid to water with cooling and agitation, never the reverse, and never in a sealed vessel.
Packaging and how it affects landed cost
| Pack | Typical volume | Best suited to |
|---|---|---|
| Carboy | 30–35 kg | Laboratory, small batch dosing, trials |
| HDPE drum | 200–250 kg | Intermittent plant consumption |
| IBC tote | 1,000–1,400 kg | Steady mid-volume use with a fixed dosing point |
| Road tanker | 15–30 tonnes | Continuous bulk consumption with tank farm storage |
Bulk is cheaper per tonne but only if you have compliant storage, bunding and unloading procedure. Where consumption is irregular, drums or IBCs often deliver a lower total cost than a tanker that leaves acid sitting in a tank absorbing moisture and picking up iron.
Where it is used, and what that implies for grade
Phosphate fertiliser production is the largest single consumer of sulfuric acid, both worldwide and among Pakistani industrial users. Consumption is predictable enough to plan procurement against.
| Fertiliser product | Approx. H₂SO₄ per tonne |
|---|---|
| Single Superphosphate (SSP) | 320–380 kg |
| Triple Superphosphate (TSP) | 600–650 kg |
| Diammonium Phosphate (DAP) | 500–550 kg |
| Ammonium Sulphate | ~735 kg |
- Metal pickling — 10–25% solution at 60–80 °C to strip mill scale before galvanising or cold rolling; technical grade is adequate
- Petroleum alkylation — 88–99% acid acting as catalyst, withdrawn as spent acid at around 88–90% and replaced on a cycle
- Textile processing — wool carbonising, acid dye bath pH control and effluent neutralisation ahead of NEQS discharge limits
- Battery manufacture — 29–32% electrolyte grade against tight iron and chloride limits
- Water and effluent treatment — pH correction, where dilute grade and low chloride matter more than assay
What to put on the RFQ
A sulfuric acid enquiry that gets a firm, comparable quotation first time contains the following. Anything missing here is something a supplier has to assume, and assumptions are where price and specification drift apart.
- Concentration and tolerance — for example "98% ± 0.5%", not "concentrated"
- Quantity per delivery and expected annual volume — the second figure changes the price more than the first
- Named limits for iron, chloride and colour where your process is sensitive to them
- Pack type — carboy, drum, IBC or tanker — and whether you can return or need to dispose of packaging
- Delivery city and site access, including whether the site can receive a road tanker
- Documentation required — certificate of analysis, MSDS, and import documents where relevant
- Whether a pre-shipment sample is needed for a first order
Checking quality on delivery
The certificate of analysis should be batch-specific and should name the actual measured values, not just restate the specification limits. A COA that reads exactly like the spec sheet for every batch is a document, not a measurement.
- Confirm the batch or lot number on the COA matches the number on the pack or tanker seal
- Check assay by titration on receipt for bulk deliveries — it is a fast, cheap test and it settles disputes before offloading
- Inspect colour against a previous accepted batch; an unexplained darkening is worth querying before use
- For battery and food-adjacent grades, confirm the COA reports iron and heavy metals rather than marking them "conforms"
- Record the tanker seal number at arrival and confirm it is intact
What drives the price
Sulfuric acid pricing in Pakistan moves on a small number of factors. Understanding them makes the difference between a quotation that looks expensive and one that genuinely is.
- Sulphur feedstock cost — most sulfuric acid traces back to elemental sulphur recovered from natural gas and refinery operations, and sulphur pricing moves with those sectors
- Concentration — you are buying acid content, so 98% is not simply "more expensive than 93%"; compare on a per-tonne-of-H₂SO₄ basis
- Pack format — bulk tanker is the lowest unit cost, carboys the highest, with the gap widening as volume rises
- Freight and delivery city — road distance from port and industrial hub matters, particularly for tanker movements
- Exchange rate and import duty on imported material or imported sulphur feedstock
- Order regularity — a scheduled call-off against an annual volume prices differently from a one-off spot purchase
Sourcing considerations in Pakistan
Sulfuric acid is available both from domestic production and by import. For a buyer, the practical differences are lead time, documentation and consistency between batches rather than the chemistry itself.
- Concentrated acid is a Hazard Class 8 corrosive — road movement requires appropriate vehicle, placarding and driver competence, and site access needs to be confirmed before a tanker is dispatched
- Confirm your storage is compatible before ordering bulk; the tank material decision follows the concentration, not the other way round
- For imported material, ask for the import documentation trail alongside the COA — it is what gives a procurement audit a complete record
- Where supply continuity matters more than unit price, diversified sourcing across more than one manufacturer is what protects you during a shortage