Sulfuric acid (H₂SO₄) is the most widely produced industrial chemical in the world. It is sold in several grades that differ in concentration and purity, and choosing the right one affects both your process and your costs. This guide explains the main grades, what each is used for and how to handle and store them safely.
Quick comparison of sulfuric acid grades
| Grade | Typical concentration | Purity focus | Main uses |
|---|---|---|---|
| Technical / industrial | 93–98% | Standard industrial specification | Fertilisers, mining and leaching, metal processing, pH control, chemical production |
| Battery grade | Concentrated acid, or diluted electrolyte (around 30–40%) | Very low iron and heavy metals | Lead-acid battery electrolyte |
| Food grade | Various | Meets food additive standards (E513) | pH adjustment in food and beverage processing, sugar refining |
| Reagent / laboratory | 95–98% | Highest purity, certified impurity limits | Laboratory analysis, electronics, pharmaceuticals |
| Oleum (fuming) | H₂SO₄ with dissolved SO₃ | Contains free SO₃ | Sulfonation, specialty chemical synthesis |
Exact specifications vary by producer, so always check the Certificate of Analysis for the batch you buy.
Technical (industrial) grade
Technical-grade sulfuric acid, usually supplied at 93–98%, is the workhorse grade. It covers most bulk applications where trace impurities do not matter:
- Fertiliser production: phosphoric acid and ammonium sulfate manufacture, the largest single use worldwide.
- Mining and metallurgy: heap and tank leaching of copper, uranium and other ores, and electrolyte make-up in copper electrowinning.
- Water and wastewater treatment: pH reduction and alkalinity control, for example to neutralise caustic effluent.
- Chemical manufacturing: production of aluminium sulfate, detergents, pigments and other chemicals.
- Metal processing: steel pickling and surface treatment.
Battery grade
Lead-acid batteries need sulfuric acid with very low levels of iron, chloride and heavy metals, because impurities increase self-discharge and shorten battery life. Battery grade is sold either as concentrated acid for dilution on site or as ready-to-use electrolyte, typically around 30–40% depending on the battery design. Electrolyte at or below 51% is transported as “battery fluid, acid” (UN 2796).
Food grade
Food-grade sulfuric acid (E513) meets the purity requirements for use as a processing aid and acidity regulator. It is used for pH adjustment in food and beverage production, in sugar and starch processing, and for cleaning food-processing equipment. Buyers need the relevant food-grade certification from the supplier.
Reagent grade and oleum
Reagent grade has certified, very low impurity limits for laboratory, electronics and pharmaceutical work. It is more expensive and usually bought in smaller packs. Oleum (fuming sulfuric acid) contains extra dissolved sulfur trioxide and is used as a strong sulfonating agent in specialty chemical production. It needs specialised handling.
How to choose the right grade
- Check your process tolerance for impurities. If iron or heavy metals would harm your product, as in batteries, food or electronics, you need a higher-purity grade.
- Compare cost per tonne of 100% H₂SO₄. Concentrated 98% acid is usually cheaper to transport than buying diluted acid.
- Consider your storage. Concentrated acid can be stored in carbon steel, but dilute acid corrodes steel quickly and needs HDPE, lined steel or other resistant materials.
- Ask for the CoA and SDS before ordering, and confirm the specification against your process needs.
Safe handling and storage
- Always add acid to water, never water to acid. Diluting sulfuric acid releases a lot of heat and can boil and spatter violently.
- Concentrated acid absorbs moisture from the air and becomes more corrosive to steel as it dilutes, so keep tanks sealed and fitted with desiccant breathers.
- Keep it away from bases, metals, organic materials and especially sodium hypochlorite, because mixing acid with hypochlorite releases toxic chlorine gas.
- Wear an acid-resistant face shield, goggles, gloves, apron and boots, and keep an eyewash station and safety shower nearby.
- Store it in bunded areas with secondary containment sized for the largest tank.
- Concentrated sulfuric acid ships as UN 1830, Class 8 (Corrosive).
Buy sulfuric acid in bulk
Saeby Chemical supplies sulfuric acid for industrial, mining and water treatment use, with a Certificate of Analysis and SDS for every batch. For pH control alongside alkalis, see also our caustic soda range. Contact us with the grade, concentration, volume and destination you need for a quotation.
Related guides: How to Store and Handle Sodium Hypochlorite Safely · Caustic Soda Flakes vs Pearls vs Liquid
