[Music] [Music] one ingredient you will need is aluminum sulfate look in the spice section of your local supermarket for alum check the ingredients this one states that it is aluminum sulfate here's one that is ammonia aluminum sulfate you don't want this one here's one that I was unable to determine exactly what it is a good option is simply to make your own aluminum sulfate the formula for the reaction is shown here and has been normalized to 1 gram of aluminum now will yield about 6.3 4 grams of aluminum sulfate I want to make about 25
grams so I multiply everything by 4 here are the ingredients you'll need 4 grams of aluminum foil 250 milliliters of water 24 grams or 93 percent sulfuric acid the acid is a little bit in excess I'll explain why later so the first thing we do is add the acid to the water I poured the dilute acid solution over the aluminum foil and covered the beaker with a watch glass the watch glass will slow the evaporation of water as the solution will become heated during the process this reaction is very slow to start and will require
heating to get it moving along I started the reaction about 20 minutes past 3:00 let's see how long it takes to react all of the aluminum so I checked the temperature just to see how it's coming along reaction seems to be going slowly at this time a couple of minutes later you can see the hydrogen starting to come off of the aluminum about 15 minutes in it's boiling it's going quite vigorously after about a half hour I'll remove the beat recover and I poke the aluminum down into the acid using that glass stir rod the
reaction has now been going for a little over one hour now we are a little past in one in one half hour mark I give it another stir two hours now and the reaction has slowed considerably I decided to add some water at this point to restore the volume back to the original 250 milliliters it's now been four hours since I started the process and all the aluminum has been consumed I checked the pH of the solution to see if it is still acidic if the solution becomes neutral or basic some of the aluminum sulfate
may hydrolyze with the water in form aluminum hydroxide the pH is about four which should be fine I try to clean up the solution first by using an ordinary coffee filter the solution goes through the filter very quickly but so does most of the impurities next I try one of my favorite methods to remove stubborn impurities I place a ball of cotton into the neck of the funnel then pour the solution through this time the results are much better and I proceed to the next step in making potassium alum potassium sulfate must be added to
the aluminum sulfate to produce potassium aluminium sulfate potassium solemate sulfate may be found in most garden centers but you should clean it up by recrystallization before using it here's this an example of what I've done using the assumption that I have 25 grams of aluminum sulfate in solution I've laid out 12 point 7 5 grams of potassium sulfate which is the one-to-one molar ratio between potassium and aluminum sulfate later much of the water has been removed and I have a little under 100 milliliters of solution remaining I had intended to stop a little sooner we
have set 125 or 150 milliliters but time got away from me and I overshot the mark a little sorry moved the beaker from the hot plate and set it aside to cool a little over an hour later just cooled to room temperature but no crystals have yet formed I decide to place the beaker in the refrigerator and let it set overnight to see what happens the next day I remove the beaker and try it into my disappointment I see that no crystals have formed perhaps removing tea much wider causes this problem because each alum molecule
requires 12 water molecules to form a crystal that's just speculation it could also be that there is simply was no seed crystal to get the process started so I won the solution back up and add some more water to increase the volume I don't show it in this video but I did filter the solution again and was able to remove some more impurities so I set the beaker aside and allow it to cool back to room temperature this time I see there's several large crystals have formed in the bottom of the beaker I decide to
place it back into the refrigerator to try and grow them even larger after a couple of hours I checked the progress and see that there are indeed larger crystals so IG can't the liquid and save it for later after a little difficulty I managed to break apart two crystals and remove them from the beaker I placed them on a paper towel covered with a piece of paper to allow them to dry so after removing more of the water from the remaining solution they set it aside to cool after an hour or so I see more
crystals have formed so by this time you know the drill I want to recover as much product as possible so I go through the process one more time this time there is very little solution remaining and it will be discarded any remaining impurities should be in this liquid so after all the crystals have dried I've separated out two larger ones from the smaller I may try and recrystallize of smaller ones later so I weigh the crystals and compare the theoretical to the actual amount the calculation shows that I have a 99.4% yield which seems a
little too good to be true perhaps the crystals are not completely dry yet here are some magnified views of some of the larger crystals [Music] you [Music]
