Content

• To step
• Part 1 of 3: Calculating the dilution
• Part 2 of 3: Creating a safe work environment
• Part 3 of 3: Diluting the acid
• Tips
• Warnings
• Necessities

It is recommended that you purchase acid that has been diluted as much as possible for your purpose, for safety and convenience, but sometimes it is necessary to dilute it even further at home. Do not skimp on safety equipment, as concentrated acids can cause severe burns. When calculating the amount of water and acid that you need for the dilution, you will need to know what the molar concentration (M) of the acid is and the molar concentration you want to obtain after the dilution.

To step

Part 1 of 3: Calculating the dilution

1. See what you already know. Find the concentration of the acid on the label or in the statement you are working on. This number is often written in the unit molarity, abbreviated to M. For example, an acid labeled "6M" contains moles of acid molecules per liter. We call this the initial concentration C.₁.
   • The formula below also uses the term V.₁. This is the volume of the acid that we are going to add to the water. We probably won't be using the whole bottle of acid, so we don't know what this number will be yet.
2. Decide what you want the end result to be. The desired concentration and volume of the acid is usually determined by the assignment from school or the requirements of the lab where you work. For example, you want to dilute the acid to a concentration of 2M, and you need 0.5 liter for this. We call this the desired concentration C.₂ and the desired volume V.₂.
   • If you are using unusual units, convert them all to molar concentration (moles per liter) and liters before continuing.
   • If you are not sure what concentration or volume of the acid is required, ask your teacher, a chemist, or an expert in the field for which you intend to use the acid.
3. Write down the formula for calculating the dilution. When you prepare to dilute a solution, you can use the formula C.₁V.₁ = C₂V.₂ This means: "the initial concentration of the solution x its volume = the diluted concentration of the solution x its volume." We know this is correct because concentration x volume = the total amount of the acid, and the total amount of the acid will remain the same when we add it to the water.
   • In our example, we can write this formula as (6M) (V₁) = (2M) (0.5L).
4. Solve the formula for V.₁. This term, V.₁will tell us how much of the initial solution to add to the water to arrive at the desired concentration and volume. Rewrite the formula as V.₁= (C₂V.₂) / (C₁), and enter the variables whose value is known.
   • In our example, we end up getting V.₁= ((2M) (0.5L)) / (6M) = 1/6 L. This is approximately equal to 0.167 L or 167 milliliters.
5. Calculate how much water you need. Now V₁ is known, the amount of acid you will be using, and V.₂, the amount of solution you end up with, you can easily calculate how much water you need to make the difference. V.₂ - V.₁ = the required volume of water.
   • In our case, we end up getting 0.5 L and using 0.167 L of the acid. The amount of water we need = 0.5L - 0.167L = 0.333 L, or 333 milliliters.

Part 2 of 3: Creating a safe work environment

1. Read the relevant Chemical Safety Cards on the internet. International Chemical Safety Cards provide concise and detailed safety information. Search for the exact name of the acid you want to use, such as "hydrochloric acid," in the online database. Some acids require additional safety precautions other than the ones below.
   • Sometimes you will need multiple cards, depending on the concentration and additions to the acid. Choose the card that best suits the acid solution you started with.
   • If you prefer to read them in another language, select it here.
2. Wear splash goggles, gloves and a lab coat. Safety glasses that protect all sides of your eyes are required when working with acids. Protect your skin and clothes by wearing gloves and a lab coat or apron.
   • If you have long hair, tie it together before working with the acid.
   • Acid can take hours to burn a hole in your clothes. Even if you don't notice a spill, a few drops may be enough to damage your clothes if not protected by a lab coat.
3. Work with a fume hood or in a ventilated area. Whenever possible, keep the acid solution in a functioning fume hood while working. This minimizes exposure to gaseous vapors produced by the acid that can be corrosive or toxic. If there is no fume cupboard available, open all windows and doors, or turn on a fan to ventilate the room.
4. Know where there is running water. If any acid gets in your eyes or on your skin, rinse it quickly with cool, running water for 15–20 minutes. Do not start diluting the acid until you know where the nearest place to wash your eyes or a sink is.
   • While washing your eyes, keep them wide open. Rotate your eyes by looking up, right, down, and left to make sure your entire eye has been flushed.
5. Have a plan ready in case you spill something, specific to the type of acid you're working with. You can purchase an acid cleaning kit that contains all the necessary materials, or purchase the neutralizers and absorbents separately. You can use the procedure described here for hydrochloric, sulfuric, nitric, or phosphoric acid, but for other acids you may need to do more research to get rid of them responsibly:
   • Ventilate the area by opening windows and doors, and turning on the fume hood and fans.
   • Sprinkle one weak base such as sodium carbonate, sodium bicarbonate or calcium carbonate over the outer edges of what has been spilled to prevent further splashing.
   • Slowly work your way from the outside in, until anything that has been spilled is covered again.
   • Mix well with a plastic stir stick. Check the pH of the spilled acid with litmus paper. Add more of the base if necessary to get the pH between 6 and 8, then flush the spilled neutralized acid down the sink with plenty of water.

Part 3 of 3: Diluting the acid

1. Cool water in an ice bath when working with concentrated acid. This step is only necessary when working with extremely concentrated acid solutions, such as 18M sulfuric acid or 12M hydrochloric acid. Cool the water you will be using by placing it in a bottle surrounded by ice at least 20 minutes before diluting the acid.
   • For most dilutions, the water can be at room temperature.
2. Put distilled water in a large bottle. If you are working on a project that requires accurate measurements, such as a titration, use a measuring cylinder. In most cases, however, an Erlenmeyer is sufficient. In any case, you will need to use a bottle that can hold enough water and with enough space to minimize the risk of spillage.
   • There is no need to measure the water very precisely, as long as it comes out of the bottle well has been accurately measured, so that you know for sure that you have the required amount of water.
3. Add a minimal amount of acid. If you are using a small amount of acid, use a (Mohr) pipette or a volume pipette with a rubber bulb on top (burette). If you need larger units, place a funnel in the neck of the bottle and slowly pour a small amount of the acid into the bottle using a graduated cylinder.
   • Never use a mouth pipette in a chemical lab.
4. Let the solution cool down. Strong acids can generate a lot of heat when water is added. If the acid is highly concentrated, the solution may splash or produce corrosive vapors. If this happens, you will need to complete the dilution in small doses or cool the water in an ice bath before continuing.
5. Add the remaining acid in small doses. Let the solution cool between each dose, especially if you notice heat, fumes or splashes. Continue to dilute until the required amount of acid has been added.
   • You calculated this quantity as V.₁ up here.
6. Stir the solution. For best results, stir the solution with a glass stir stick after each addition of the acid. If the size of the bottle makes this impractical, stir the solution after diluting the acid completely and removing the funnel.
7. Put away the acid and rinse the tools. Pour the acid solution you have made into a clearly labeled bottle, preferably PVC coated, and store it in a safe place. Rinse the bottle, funnel, stir stick, pipette and / or measuring cylinder with water to remove all traces of acid.

Tips

• Always add acid to the water, never the other way around. When the substances come into contact with each other, they produce a lot of heat. The more acid is involved, the more heat you will have to dissipate (cooling) to absorb this, and thus prevent boiling and splashing.
• A reminder for the correct order: "water with acid, creates fire".
• When mixing two acids, always add the strongest acid to the weaker one for the same reason as above.
• It is possible to add half of the water first to dilute the acid completely, then slowly add the rest of the water, this is not recommended for concentrated solutions.
• Get the most dilute version of the acid you need for maximum safety and easy storage.

Warnings

• Even if the acidic effects are not very strong, the acid in question can still be very toxic. An example is hydrocyanic acid (not very strong but very poisonous).
• Never try to counteract the effects of acid spills with a strong lye, such as KOH or NaOH. Instead, use water or a weak base such as dilute sodium hydrogen carbonate (NaHCO3).
• Don't dissolve materials just for fun or for whatever reason, unless you really know what you're doing. It can happen that you create hazardous substances in this way, such as toxic or explosive gases that ignite spontaneously.
• So-called "weak" acids can also produce a lot of heat and are very dangerous. The distinction between strong and weak acids is only chemical.

Necessities

• Safety glasses
• Gloves
• Lab coat or apron
• Eyewash station (access to cool, running water that you can easily cover your eyes)
• Volumetric flask (for the greatest precision), or an Erlenmeyer
• Pipette (for small quantities), or a graduated cylinder (for larger ones)
• Water
• Acid
• Acid spill kit (to clean up spilled acid), or sodium bicarbonate and a plastic tool
• Glass stir stick