Wednesday, January 13, 2010

Copper Sulfate Preparation

How to Make Copper Sulfate or Copper Sulphate

Copper sulfate crystals are among the most beautiful crystals you can grow, but you might not have access to a chemistry lab or want to order the copper sulfate from a chemical supply company. That's okay, because you can make copper sulfate yourself using readily-available materials.
Materials for Making Copper Sulfate

There are actually a few different ways you can make copper sulfate yourself. This method relies on a little electrochemistry to get the job done. You will need:

copper wire - which is high purity copper
sulfuric acid - H2SO4 - battery acid
6-volt battery
Make Copper Sulfate
Fill a jar or beaker with 5 ml concentrated sulfuric acid and 30 ml of water. If your sulfuric acid solution is already diluted, add less water.

Set two copper wires into the solution so that they are not touching each other.

Connect the wires to a 6-volt battery.

The solution will turn blue as copper sulfate is produced.
When you run electricity through copper electrodes which are separated from each other in a dilute sulfuric acid bath the negative electrode will evolve bubbles of hydrogen gas while the positive electrode will be dissolved into the sulfuric acid and oxidized by the current. Some of the copper from the positive electrode will make its way to the anode where it will be reduced. This cuts into your copper sulfate yield, but you can minimize the loss by taking some care with your set-up. Coil the wire for the positive electrode and set it at the bottom of your beaker or jar. Slip a piece of plastic tubing (e.g., a small length of aquarium hose) over the wire where it extends up from the coil to keep it from reacting with the solution near the anode. (If you had to strip your wire, just leave the insulating coating on the part that runs down into the liquid). Suspend the negative copper electrode (anode) over the cathode coil, leaving a good amount of space. When you connect the battery, you should get bubbles from the anode, but not the cathode. If you get bubbling at both electrodes, try increasing the distance between the electrodes. Most of the copper sulfate will be at the bottom of the container, separated from the anode.
Collect Your Copper Sulfate

You can boil the copper sulfate solution to recover your copper sulfate. Because the solution contains sulfuric acid, you won't be able to boil the liquid off completely (and you need to take care not to touch the liquid, which will become concentrated acid). The copper sulfate will precipitate out as a blue powder. Pour off the sulfuric acid and reuse it to make more copper sulfate!

If you would prefer to have copper sulfate crystals, you can grow them directly from the blue solution that you prepared. Just allow the solution to evaporate. Again, use care in recovering your crystals because the solution is very acidic.

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