Experiment date: 2013/11/1

Principle:

     Recrystallization is a way to purify chemicals. In this experiment, the solvent is playing an important part. We need to choose the right ones to make it useful. There are two way that usually used. the first one, just heat the solvent and put the thing what you want to pure. Then cold the solvent and the chemical you put will came back to solid. The second one is by using two difference of the solubility between two solvent. This two solvent should have two solubility. One is high and one is low. Heat the higher one and dissolute the chemical in it. Then put the other solvent in it until it start to smoke and won’t disappear for five second.

        And about recycling Al. Alum can grow in the solvent with X³⁺ and Y^-. in the right situation it can be a crystal.

Chemicals and their Properties:

KAl(SO4)2·12H2O: CAS: 10043-67-1 258.205 g/mol d: 1.725 g/cm³ BP:200 °C

                 MP: 92–93 °C   Solubility :14.00 g/100 mL (20 °C)

Aluminium: CAS: 7429-90-5 d: 2.70 g/cm³ BP: 2519 °C MP: 660.32 °C  

Safety and Waste Disposal:

Don’t heat the organic solvent directly.

Procedure:

(1)Choose the right solvent. You can choose the right one by testing it or find its info.

And heat it. But be careful some solvent can’t by fire directly. Then dissolute the

chemicals.

(2)You can use charcoal to take away the impurity.

(3)To take away the impurity which isn’t adsorption by charcoal. You can filtrate it.

(4)You can choose two ways to grow the crystal. By just put it down and don’t move it. Or you can put a little crystal in and the crystal will grow on it. Then you need to cold it down.

(5)To get the crystal. You can use decompression filtration system. The filter paper should be fold that it can be just fit the funnel. After filtrate it you should wash it.

(6)You can dry the crystal by decompression, heat or by using a desiccator.

(7)As the picture says .