Acids and Assessed Practicals

Diluting acids can often be complex and often risky process, which you may only do a few times a year. Our guide on how to dilute acids safely tell you everything you need to know.

Before you start, it’s important that the dilution of acids is carried out on a safe manner. Please make sure all of these steps are followed beforehand.

Read the relevant Chemical Safety Cards online or consult the MSDS. International Chemical Safety Cards provide succinct, detailed safety information. Search for the exact name of the acid you will be using, such as "hydrochloric acid," in the online database. Some acids may require additional safety precautions, besides those described below.

Wear splash goggles, gloves, and a lab coat. Splash safety goggles that cover all sides of the eyes are required when handling acid. Protect your skin and clothing by wearing gloves and a lab coat or apron

Work in a fume cupboard or ventilated area. Whenever possible, keep the acid solution in a functioning fume cupboard while you are working. This limits exposure to gaseous vapors produced by the acid, which can be corrosive or poisonous.^[2] If a fume cupboard is not available, open all windows and doors, or turn on a fan to ventilate the area.

Know where running water is located. If acid gets on your eyes or skin, you'll need to flush it with cool, running water for 15–20 minutes. Don't start the dilution until you know where to find the nearest functioning eye wash station or sink.

Have a spill plan ready, specific to your acid. You can purchase an acid spill kit that contains all the necessary materials or acquire neutralizers and absorbers separately. The process described here can be used for hydrochloric, sulfuric, nitric, or phosphoric acid, but other acids may require further research to dispose of properly. Why not check out our Philip Harris Spill Kit below?

1. Cool water in an ice bath when using concentrated acids. This step is only necessary when you'll be handling extremely concentrated acid solutions, such as 18M sulfuric acid, or 12M hydrochloric acid.^[4] Cool the water you'll be using by keeping it in a container surrounded by ice for at least 20 minutes before the dilution begins
2. Add distilled water to a large flask. For projects involving careful measurement, such as titration, use a volumetric flask. For most practical purposes, an Erlenmeyer flask can be used instead. In either case, choose a container that can easily contain your total desired volume, with plenty of space remaining, to minimize splashes over the rim.
3. Add a tiny quantity of acid. If using a small volume of acid, use a graduated (Mohr) pipette or volumetric pipette with a rubber bulb on top. For larger volumes, place a funnel in the neck of the flask, and slowly pour in a small quantity of the acid using a graduated cylinder
4. Allow the solution to cool off. Strong acids may generate lots of heat when added to water. If the acid was highly concentrated, the solution may splatter or produce corrosive fumes. If this happens, you will need to perform the entire dilution in very small doses or cool the water in an ice bath before you continue.
5. Add the remaining acid in small doses. Allow the solution time to cool off between each dose, especially if you notice heat, fumes, or spatter. Continue until the required amount of acid has been added.
6. Store the acid and rinse the tools. Pour the acid solution you created into a clearly labeled container, preferably a PVC coated glass bottle, and store in a safe location. Rinse the flask, funnel, stirring rod, pipette, and/or graduated cylinder in water to remove all traces of acid. Want to make sure your acids are stored safely? Read our blog on the latest Government guidance on chemical storage.