Experiment One – Purifying Iron Sulphate
We will use three different processes to carry this out:
1. Dissolving-> iron sulphate in water
2. Filtering-> a solid from a liquid
3. Crystallisation-> growing crystals from a saturated solution
Use a measuring cylinder to place 40mL of water in a 150mL beaker. Add 5mL of dilute sulphuric acid (CARE). Obtain a sample (about 30g in a film canister) of impure iron sulphate (from the garden store), place it into a beaker. Place the beaker on a gauze mat on a tripod, and warm the solution, stirring from time to time. Most of the impure iron sulphate should dissolve. DO NOT BOIL.
Filtering (or filtration)
Is a process for separating a mixture of a liquid and a solid, when the solid doesn’t sink down or settle to the bottom.
a) Fold a filter paper in half, then in quarters, then open up as shown:
b) Place the folded filter paper into a funnel, and wet it with water, to make it fit snugly in the funnel. Place the funnel safely in a ring clamp. Use this filter to separate the greenish liquid from any undissolved material by pouring the mixture into the paper. Do not allow the liquid to come above the edge of the paper.
Allow the hot (or warm) concentrated iron sulphate solution to stand and cool down, possibly overnight. Crystals of pure iron sulphate should form. Next period, obtain the crystals by decanting the liquid off. Describe the crystals of iron sulphate, which have the formula FeSO4 7H2O.