dilutioncalculator.co.uk§ Verified 20 Jun 2026 · Reviewed by A. Hargreaves, MChem (Hons)

Add acid to water

A short, flat safety statement. Water goes in first. Acid goes in second, slowly. The reverse pour causes a localised exothermic boil-back.

§ 1Why

Dilution of concentrated H₂SO₄ in water releases ~75 kJ/mol of heat. Adding water to acid puts a small drop of water onto a large body of concentrated acid; the water boils instantly and ejects acid as a spray. Adding acid to water disperses the heat into a larger reservoir.[12]

§ 2PPE

  • Splash goggles (BS EN 166 grade 3 chemical splash).
  • Nitrile gloves over an arm-cuff that covers the wrist.
  • Lab coat, sleeves rolled down.
  • Acid-resistant apron for >1 L work.
  • Fume cupboard for concentrated H₂SO₄ and HNO₃.

§ 3Related