Sciencemadness Discussion Board

aluminum sulfate - can I use it to make anything useful

jamit - 17-2-2012 at 01:16

I have fertilizer grade aluminum sulfate. What can I do with it? One thing I would like to try is to make alum, aka, potassium aluminum sulfate. However I'm at a lost. How would I go about making it? Many experiments on google mentions using aluminum can and KOH and sulfuric acid to make alum. How can I get potassium ions added to the aluminum sulfate? Should I add KOH? Should I add potassium carbonate?

What other things can you make with aluminum sulfate? I don't necessarily need detail, unless you want to share some, just some ideas and directions. Thanks.

Hexavalent - 17-2-2012 at 03:36

Firstly, double salts are often right ***** to make as the ions often will not arrange themselves as you want.

Aluminium sulfate, however, is a really nice starting material for making various aluminium salts, e.g. the carbonate, oxide, phosphate etc. via precipitation and it may have a nice use for some electrolysis experiments, too.

jamit - 17-2-2012 at 03:42


Thanks for sharing your thought on the possible uses for aluminum sulfate. But are your suggestions based on experience. Have you experimented anything yourself using aluminum sulfate?

ldanielrosa - 17-2-2012 at 04:00

Mix with calcium nitrate to yield aluminum nitrate and precipitate calcium sulfate. Nurdrage has an experiment that uses aluminum nitrate, and this is a bit less messy than the two acids route.

ScienceSquirrel - 17-2-2012 at 04:09

You can buy potassium sulphate at garden centres.
Alum is a very easy double salt to make and crystallises very well. It is one of the easiest salts to use to grow large crystals.

Hexavalent - 17-2-2012 at 05:11

Really? How would one go about making a double salt then? I've never got them to work:(

ScienceSquirrel - 17-2-2012 at 05:37

Just mix equivalent amounts of potassium sulphate and aluminium sulphate solutions.
Or follow one of the aluminium can, potassium hydroxide, sulphuric acid recipes.

Mr. Wizard - 17-2-2012 at 10:44

Aluminum cans are rarely pure aluminum. They contain magnesium, copper, silicon, and other metals needed to give the alloy it's ability to be formed into a can. Even the top of the can and the bottom are different alloys. There was a article 10-20 years ago in the Scientific American about the delicate balance required to get the cans to work as expected. Wickipedia gives this information "The aluminium used in United States and Canada are alloys containing 92.5% to 97% aluminium, <5.5% magnesium, <1.6% manganese, <0.15% chromium and some trace amounts of iron, silicon and copper according to MSDS from aluminium producer Alcoa"

Aluminum foil is a more pure form of the metal, as is heavy electrical cable. Be aware some heavy cabling has a steel strand in it's center to carry the weight of the cable. This strand is easily found and removed.

If you want pure compounds you may want to consider your source of 'aluminum'.