How to Buy Phosphoric Acid: A Buyer’s Guide
Phosphoric acid (H3PO4, CAS 7664-38-2) is a commodity mineral acid, but it is not one product. Before you request a quotation you need to fix three things: concentration, grade and delivery form. Get those right and the rest of the purchase is straightforward; get them wrong and you either pay for purity you do not need or fail the specification your process actually requires. This guide covers what to confirm on a phosphoric acid enquiry.
1. Concentration: 75% or 85%
The two commercial strengths are 75% and 85% H3PO4 as aqueous solutions. The 85% material is the standard export and shipping strength; 75% is a common strength where a less concentrated acid is easier or safer to handle, or where the process does not need the highest strength.
| Concentration | Typical density (20 deg C) | Typical use |
|---|---|---|
| 75% H3PO4 | Approx. 1.58 g/cm3 | Metal treatment, cleaning, acidulation where 85% is not required; easier handling |
| 85% H3PO4 | Approx. 1.69 g/cm3 | Standard commercial strength; food grade and most industrial uses |
Because the concentration changes the density, the acid is usually bought by weight, not by volume. Confirm whether your quotation is on a net-weight or net-volume basis, and whether the concentration is guaranteed on the COA for each batch.
2. Grade: industrial or food grade
Grade – not concentration – decides what the acid may be used for. Food-grade acid is defined by strict limits on arsenic, fluoride and heavy metals; industrial acid is supplied against an industrial specification for lower-cost process use.
| Property | Industrial / technical grade | Food grade (E338) |
|---|---|---|
| Concentrations available | 75% and 85% | 85% only |
| Control of arsenic / heavy metals | Per industrial specification | Strictly limited to food-grade levels |
| Fluoride | Per industrial specification | Tightly limited |
| Typical use | Phosphating, water treatment, cleaning, catalysis | Soft drinks, jams, processed foods, food processing |
If your application is food or beverage, you need the food grade at 85%; it can be diluted to a lower working strength in your plant, but food grade is not normally supplied at 75%. If your application is metal treatment, water treatment or general industry, industrial grade at either strength is usually the economical choice.
3. Wet-process vs thermal acid
Behind the grade sits the production route. Wet-process acid (phosphate rock digested with sulfuric acid) is cheaper and is used for fertilisers and many industrial phosphates. Thermal-process acid (elemental phosphorus burned and absorbed in water) is purer and is the basis of food-grade and high-purity acid. When you buy a high-purity or food grade, you are buying the thermal route; when you buy a bulk industrial acid for phosphating, the wet route may be acceptable if the specification is met.
4. Specifications to request
Ask for a specification sheet and confirm that the batch COA will report at least the following:
| Parameter | Why it matters |
|---|---|
| Assay (H3PO4 content) | Confirms the delivered concentration and your dosing calculations |
| Arsenic | The key limit for food grade; also relevant for some technical uses |
| Fluoride | Rises with the ore source; critical for food and electronics |
| Heavy metals (as Pb) | Food-grade and regulatory limits |
| Iron, chloride, sulfate | Impurities that matter for phosphating, catalysts and electronics |
| Colour / appearance | An indicator of purity and of the production route |
5. REACH and buying for Europe
If you buy phosphoric acid for a European plant, the substance should be supplied as a REACH-registered substance so that you do not have to register it yourself. We supply phosphoric acid as a REACH-registered substance, with the specification, COA and safety data sheet (SDS) issued per batch. Confirm the exact status and paperwork you need when you request a quotation.
6. Packaging and delivery
| Form | Typical use |
|---|---|
| Plastic drums (e.g. 35 kg net) | Small volumes, laboratory and pilot use |
| IBC / intermediate bulk container (1000 L) | Regular plant use; fork-lift handling |
| Bulk tanker / ISO tank | Large-volume industrial or food use |
Phosphoric acid is corrosive and is shipped in acid-resistant containers. For food-grade material, confirm that packaging and transport are suitable for food contact.
7. Storage and handling in your plant
- Corrosive. Concentrated acid attacks skin, eyes and tissue; use chemical goggles, gloves and protective clothing.
- Containers. Store in acid-resistant vessels (for example stainless steel or approved plastics) kept closed and clearly labelled.
- Incompatibilities. Keep away from strong bases and reactive metals; neutralise spills carefully.
- Documentation. Keep the SDS accessible; consult it for first aid and transport information.
8. Supplier checklist
- Confirms the concentration (75% or 85%) and the grade (industrial or food grade).
- Provides a specification sheet and per-batch COA and SDS.
- States REACH status for EU purchases.
- Offers the packaging and delivery form you need.
- Quotes on the basis (weight or volume) you asked for, with lead time and Incoterms.
Frequently Asked Questions
What concentrations can I buy?
75% and 85% H3PO4 as aqueous solutions. The 85% grade is available in industrial and food grades; the 75% grade is available as industrial acid.
Is food-grade phosphoric acid available at 75%?
Food-grade acid (E338) is supplied at 85%, the standard commercial strength for food use. It can be diluted to a lower working strength in your plant.
How do I know if I need food grade?
If the acid will contact food or beverages, or must meet a food monograph, you need food grade at 85%. For metal treatment, water treatment and general industry, industrial grade is normally sufficient.
Do you have REACH registration?
Yes – phosphoric acid (CAS 7664-38-2) is supplied as a REACH-registered substance. Confirm the exact status and documents you need when you request a quotation.
How should phosphoric acid be stored?
In closed, acid-resistant containers away from strong bases and reactive metals. Consult the safety data sheet for handling and first aid.
Can you supply both grades from one order?
Yes – tell us the concentration, grade, volume and delivery point for each line and we will quote them together.
Related reading
- Phosphoric acid (CAS 7664-38-2): properties, grades and uses
- Phosphoric acid in metal phosphating and surface treatment
- Food-grade phosphoric acid (E338): uses and selection
- Phosphoric acid (CAS 7664-38-2) – product page
PolyBlueChem supplies phosphoric acid (CAS 7664-38-2) in 75% and 85%, industrial and food grade (85% only), with REACH registration for the European market. Contact us for specifications, COA and a quotation.