Cut the weighed piece into smaller pieces, and place them a clean 250 mL beaker. Do not lose any metal bits.
7. Using a graduated cylinder, add 50 mL of 1.4 M KOH. DO IT IN THE HOOD!
8. Set up a ring stand, ring clamp, gauze, and bunsen burner. Place the beaker on the gauze and heat the beaker on a low flame. It is not necessary to boil it. The aluminum will take about 20 minutes to dissolve.
9. While it is dissolving, set up an apparatus for gravity filtration (as described by the figure on page A-3). Place a clean funnel, with a piece of folded filter paper, on a 125 mL Erlenmeyer flask.
10. When the aluminum has dissolved (as evidenced by the lack of bubbles of H2 gas given off), gravity filter the solution. Only fill the funnel to within 1/2" of the top of the paper. Use a glass rod to “guide" the solution into the paper (as demonstrated by your instructor). The solution in the Erlenmeyer flask should be both clear and colorless at this point.
11. Allow the flask to cool. While it is cooling, wash the funnel and beaker with lots of tap water to remove any potassium hydroxide.
12. When the solution is reasonably cool, add 20 mL of 9 M H2SO4 (with a graduated cylinder) quickly and with care. It is important that you swirl the flask as you add the acid. The solution will get quite warm. If there are any white flecks left in the solution after the addition of the H2SO4, place the flask on the Bunsen burner apparatus and warm it with swirling until all of the solid material has dissolved.
13. Make an ice bath by putting ice and water into a 600 mL beaker.
14. Allow the flask to cool a little and then place it in the ice bath and allow it to cool for an additional 5 minutes.
15. If alum crystals have not started to form, scratch the inside walls of the flask with a stirring rod. This provides sites at which crystallization can begin, followed by crystal formation throughout the liquid. Swirl the flask when you notice the onset of crystal formation and allow it to cool in the ice bath for another 10 minutes.
16. While the solution is cooling, pour 50 mL of 50% alcohol/water mixture into a test tube and place it in the ice bath to cool.
17. Set up the vacuum filtration apparatus (Buchner funnel) as illustrated by your instructor and on the following page. Pour some distilled water onto the filter.
18. Remove the flask containing the alum crystals from the ice bath, swirl so that all the crystals are dislodged, and pour quickly into the Buchner funnel. Keep swirling and pouring until all the solution and crystals are transferred to the funnel. The water aspirator should be kept going all through this process.
19. Pour about 10 mL of the cooled alcohol/water mixture into the flask. Swirl the flask and pour mixture into the funnel to transfer any remaining