It’s easy to make copper sulfate using readily available materials. Copper(II) sulfate is also known as copper sulphate, blue vitriol, or bluestone. Usually, it is a vibrant blue salt encountered as copper sulfate pentahydrate (CuSO4·5H2O). The chemical has several uses, but most people use it for growing blue blue copper sulfate crystals.
Here is how you make copper sulfate yourself, using a battery, copper wire, and dilute sulfuric acid.
Materials for Making Copper Sulfate
The easiest and safest method of making copper sulfate uses electrochemistry.
- Copper wire (which is high-purity copper)
- Sulfuric acid (H2SO4 or battery acid)
- 6-volt Battery
Concentrated sulfuric acid (like the kind in a lab) is 98% sulfuric acid and 2% water, with a concentration of 18.4 M. That is too strong for this project, so you need to dilute it. If you have dilute sulfuric acid, go ahead and use that. If you’re making copper sulfate at home, you’re probably using battery acid, which averages around 37% acid in water or about 4 M. You don’t need to dilute it much in this project.
While the instructions call for a 6-volt battery, a 9-volt battery or a constant power supply work fine.
Make Copper Sulfate
- Pour 30 ml of water and then 5 ml concentrated sulfuric acid into a small glass jar or beaker. Always add acid to water, not the other way around. This minimizes the chance of the acid splashing. For battery acid, use less water. The concentration of acid is not critical, so either 30 milliliters of acid in 40 milliliters of water or mixing half battery acid and half water is fine.
- Inspect your wires. If they are insulated, strip enough insulation that you have bare copper ends to put in the liquid. Attach a copper wire to each battery terminal and immerse the exposed ends in the solution to that the wires are not touching each other.
- The liquid turns blue as copper sulfate is produced.
Concentrate the Copper Sulfate
The reaction between sulfuric acid and copper yields a dilute copper(II) sulfate solution. If left undisturbed, copper sulfate crystals form as the water evaporates. However, the solution still contains some sulfuric acid, so use care when removing the crystals (which are your solid product).
Alternatively, concentrate the solution by boiling it. After evaporating the liquid, blue copper sulfate powder remains. Any remaining liquid that does boil away is concentrated sulfuric acid. Pour this liquid off and save it for future science experiments.
Once you have copper sulfate, dissolve it in water and grow copper sulfate crystals.
Tips for Success
When you run electricity through the copper electrodes, expect bubbling from the anode (negative electrode) in the liquid. These bubbles contain hydrogen gas. Meanwhile, the copper at the cathode (positive electrode) dissolves. Some of the dissolved copper ions make their way to the anode and are reduced. When this happens, it reduces the copper sulfate yield. But, a little care with the set-up reduces the loss.
If you have enough wire, coil the copper for the cathode (connected to the “+”) and place it on the bottom of the jar or beaker. Either leave the wire insulation in place above the coil or else slide a section of plastic tubing (such as aquarium tubing) over exposed wire just above the coil. This minimizes the reaction between the cathode and anode. Place the anode (connected to the “-“) higher in the liquid and distant from the coil. Ideally, hydrogen bubbles only form from the anode. If both electrodes bubble, move the copper wires further apart. With this set-up, copper sulfate forms at the bottom of the container, near the cathode.
Make Copper Sulfate Using Sulfuric Acid and Nitric Acid
While the electrochemical method is the safest way of making copper sulfate, there are other synthesis routes. Another method uses sulfuric acid, nitric acid, and copper (either as a chunk or wire). The disadvantage is that nitric acid and concentrated sulfuric acid are not common home chemicals. They come from a chemical supply store. The acid mixture is highly corrosive and produces toxic vapor, so the procedure is best done in a fume hood. This reaction is popular as a chemistry demonstration because of the color changes. Note that the product includes both copper(II) sulfate and copper(II) nitrate.
- 70% nitric acid
- concentrated (98%) sulfuric acid
- Place 30 milliliters of water in a beaker.
- Add 5 milliliters of nitric acid and 3 milliliters of concentrated sulfuric acid.
- Gently drop about 6 grams of copper into the acid solution. The reaction releases a brown gas and the solution turns blue.
- Within the fume hood, let the acid evaporate. Collect the copper sulfate crystals.
Make Copper Sulfate Using Sulfuric Acid and Hydrogen Peroxide
You can make copper sulfate from copper in a mixture of sulfuric acid and hydrogen peroxide called piranha solution. This is not a recommended synthesis method. It is not very efficient and the acid and peroxide often boil during mixing and may overflow or break a glass container. While 30% hydrogen peroxide is available from a beauty supply store, the concentrated sulfuric acid comes from a chemical supply store.
- 30% hydrogen peroxide (H2O2)
- concentrated (98%) sulfuric acid (H2SO4)
- Pour 10 milliliters of 30% hydrogen peroxide into a borosilicate glass beaker.
- Add 3 milliliters of concentrated sulfuric acid. This reaction is exothermic, so expect heat!
- Carefully add about 3 grams of copper. The copper bubbles and the clear liquid turns blue.
- Pour the liquid onto a shallow glass dish. Leave any remaining copper in the original container. Copper sulfate crystals form as the liquid evaporates.
Copper Sulfate Safety and Disposal
- Wear gloves and eye protection. Sulfuric acid is corrosive and causes burns upon contact. Do not touch or inhale the acid. In the event of a splash, immediately rinse the affected are with lots of water. Neutralize a spill using a weak acid, such as baking soda. Then, rinse with plenty of water.
- Avoid skin contact with the copper sulfate solution. Copper sulfate is a skin irritant. It is only mildly toxic, but please don’t drink the liquid. It still contains some acid and may be corrosive. In case of accidental contact, rinse affected skin with water.
- While municipal water treatment can handle copper just fine, copper sulfate is toxic to invertebrates, so don’t dump copper sulfate outdoors. Rinse unused product down the drain with plenty of water.
- Clayton, G. D.; Clayton, F. E. (eds.) (1981). Patty’s Industrial Hygiene and Toxicology (3rd ed.). Vol. 2, Part 6 Toxicology. NY: John Wiley and Sons. ISBN 0-471-01280-7.
- Copper Development Association Inc. “Uses of Copper Compounds: Copper Sulphate.”
- Wiberg, Egon; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic Chemistry. Academic Press. ISBN 978-0-12-352651-9.
- Zumdahl, Steven; DeCoste, Donald (2013). Chemical Principles. Cengage Learning. ISBN 978-1-285-13370-6.