# Chemistry Q. How do I make aluminium sulphate? **URL:** \ **Category:** Factual Questions\ **Created:** [November 17, 2003, 6:32pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740 "2003-11-17T18:32:57Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Jojo](https://avatars.discourse-cdn.com/v4/letter/j/ecd19e/32.png) [@Jojo](https://boards.straightdope.com/u/Jojo)\ **Post date:** [November 17, 2003, 6:32pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/1 "2003-11-17T18:32:57Z")
I’ve been trying to buy some alum which is a mixture of aluminium sulphate and potassium sulphate. It used to be used for purifying water but it doesn’t get used much any more so none of the pharmacies I have asked stock it. The suppliers to the pharmacies don’t seem make it either so I’m wondering how I would go about making it myself. I know next to nothing about chemistry so I thought I would ask Doperville whether anyone had any ideas. I presume I would need some aluminium, right? What about aluminium foil, could I use that? Then how would I sulphadize it? Heat it up somehow? But heating foil doesn’t seem to do anything to it…hmmm. As you can see, my knowledge of chemistry is a little thin. Does anyone know where to start? ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 17, 2003, 7:08pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/2 "2003-11-17T19:08:34Z")
You can make aluminum sulfate by pouring sulfuric acid (from the hardware store) over aluminum foil. You’ll have to neutralize any excess acid with, say, potassium hydroxide. It’s easier just to go to the local gardening store and buy a box of aluminum sulfate. It’s used as a soil additive to turn hydrangea blossoms blue. ---
**Author:** ![PbZep](https://avatars.discourse-cdn.com/v4/letter/p/58f4c7/32.png) [@PbZep](https://boards.straightdope.com/u/PbZep)\ **Post date:** [November 17, 2003, 8:32pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/3 "2003-11-17T20:32:49Z")
**Do NOT mix potassium hydroxide and sulfuric acid!** You will not like the results. I don’t know how exothermic the aluminum reaction to H2SO4 is. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [November 17, 2003, 9:13pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/4 "2003-11-17T21:13:51Z")
It’s pretty darn exothermic, once it gets going. With regard to mixing KOH with H[sub]2[/sub]SO[sub]4[/sub]: how do you think chemists neutralize acids ? They add base. Everything should be fine, unless you’re foolish enough to slosh together concentrated solutions of each, in which case, the whole mess could start boiling and spitting. ---
**Author:** ![Jojo](https://avatars.discourse-cdn.com/v4/letter/j/ecd19e/32.png) [@Jojo](https://boards.straightdope.com/u/Jojo)\ **Post date:** [November 17, 2003, 11:34pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/5 "2003-11-17T23:34:25Z")
ok so let me check I’ve got this right: I get myself a large metal pan and stand it outside. I put several sheets of foil in the bottom of the pan then I pour a pint (?) or so of diluted sulphuric acid over it. Leave to stand for a couple of minutes then pour some potassium hydroxide over it to neutralise the acid. The resultant mess in the bottom of the pan will be aluminium sulphate? Will it be safe to handle now that the acid has been neutralised? Alum also requires potassium sulphate. Any ideas as to how I make that? I tried asking at gardening stores for aluminium sulphate before posting this thread but no luck. ---
**Author:** ![Jojo](https://avatars.discourse-cdn.com/v4/letter/j/ecd19e/32.png) [@Jojo](https://boards.straightdope.com/u/Jojo)\ **Post date:** [November 17, 2003, 11:37pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/6 "2003-11-17T23:37:12Z")
Oh also - where would I buy potassium hydroxide from? What kind of shop stocks that? Chemist? Hardware store? Garden store? ---
**Author:** ![quiltguy154](https://avatars.discourse-cdn.com/v4/letter/q/ad7895/32.png) [@quiltguy154](https://boards.straightdope.com/u/quiltguy154)\ **Post date:** [November 18, 2003, 12:08am UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/7 "2003-11-18T00:08:51Z")
If you’re looking for alum, check out stores that sell supplies for home canning. Alum is used to keep cucumbers crisp once they are processed. Might be hard to find this time of year, canning season is pretty much over. If you’re in the South or Midwest, where a good deal of home canning is done, check out hardware stores and feed/grain stores. Online companies that sell herbs and spices may have it. Good luck. ---
**Author:** ![TheNerd](https://avatars.discourse-cdn.com/v4/letter/t/858c86/32.png) [@TheNerd](https://boards.straightdope.com/u/TheNerd)\ **Post date:** [November 18, 2003, 1:27am UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/8 "2003-11-18T01:27:42Z")
I was just at an asian market that had bigass bags full of crystal alum. I didn’t check the price, but it has to be easier than making it. ---
**Author:** ![Jojo](https://avatars.discourse-cdn.com/v4/letter/j/ecd19e/32.png) [@Jojo](https://boards.straightdope.com/u/Jojo)\ **Post date:** [November 18, 2003, 1:51am UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/9 "2003-11-18T01:51:04Z")
ok I found an online spice store called [The Great American Spice Company](http://www.americanspice.com/?x=1069119861&_ssess_=660b121ef5ece5121c9e9d8397548011) that claims to sell it so I’ve ordered some from them. Quote from their site: > [@](#): > > Pure Granulated Alum. Commonly used in pickling recipes to keep them crispy. Alum is one of our big sellers because it is often hard to find. Boy, they can say THAT again. You wouldn’t believe the trouble I’ve had trying to find this stuff. Anyway, thanks everyone. Hopefully this problem is sorted now. ---
**Author:** ![Myrr21](https://avatars.discourse-cdn.com/v4/letter/m/e495f1/32.png) [@Myrr21](https://boards.straightdope.com/u/Myrr21)\ **Post date:** [November 18, 2003, 2:29am UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/10 "2003-11-18T02:29:57Z")
> [@](#): > > \*Originally posted by PbZep \* > **Do NOT mix potassium hydroxide and sulfuric acid!** You will not like the results. I don’t know how exothermic the aluminum reaction to H2SO4 is. Good god, man: calm down. It’ll get a little hot; no big deal unless you’re holding the container in your bare hands. ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [November 18, 2003, 3:13am UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/11 "2003-11-18T03:13:43Z")
> [@](#): > > Good god, man: calm down. It’ll get a little hot; no big deal unless you’re holding the container in your bare hands. Actually, even a modest solution of sulfuric acid can bubble boil and spit a rather caustic solution if you add potassium hydroxide directly to it. Potassium hydroxide is a solid, and is generally sold as pellets or powder, NOT a dilute solution, so the original response was indeed potentially dangerous. I wouldn’t want to be standing anywhere near that solution if it was spitting or even misting. Whether a given displaced droplet is acid or alkaline or neutral pH, I wouldn’t H2SO4, KOH, or K2SO4 in my eyes The situation is further complicated by the fact that he wants to perform this rection in a “large metal pan” - BAD IDEA. Sulfuric acid reacts with most metals (I presume he doesn’t mean, say, a gold pan) and the entire system, including the potassium hydroxide and aluminum can wreck most common metals in various ways. A copper or brass pot could become contaminated with copper sulfate, which is the same stuff used by the recently sentenced “Slurpie poisoners” (to cite just one reaction) From the form of the question, I think we can take it for granted that the OP wouldn’t know this and take appropriate measures ---
**Author:** ![KP](https://avatars.discourse-cdn.com/v4/letter/k/a9adbd/32.png) [@KP](https://boards.straightdope.com/u/KP)\ **Post date:** [November 18, 2003, 3:17am UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/12 "2003-11-18T03:17:27Z")
Forgot to note: dissolving the KOH in water to make a dilute solution is not a completely satisfactory answer either. Solid KOH, added to plain water, can bubble boil and spit a caustic alkaline solution on a rough par with drain cleaner). I think the OP clearly didn’t know that, so I think the warning was warranted ---
**Author:** ![curly\_chick](https://avatars.discourse-cdn.com/v4/letter/c/7ba0ec/32.png) [@curly\_chick](https://boards.straightdope.com/u/curly_chick)\ **Post date:** [November 18, 2003, 8:29am UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/13 "2003-11-18T08:29:21Z")
Fisher Scientific and VWR are large international laboratory supply houses which sell, among other things, chemicals on line. Rather than attempting to make these things, when you say yourself you know nothing about chemistry, why not just buy them? I do not know what the chemical name for alum is, but you might find that one of these companies sells alum too. [Fisher](https://www1.fishersci.com/index.jsp) [VWR](http://www.vwrsp.com/) ---
**Author:** ![Myrr21](https://avatars.discourse-cdn.com/v4/letter/m/e495f1/32.png) [@Myrr21](https://boards.straightdope.com/u/Myrr21)\ **Post date:** [November 18, 2003, 12:11pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/14 "2003-11-18T12:11:21Z")
Yeah, the pan thing was a bad idea, but otherwise: chill out. I’ve added both solid and high concentration liquid base to conc acid a million times. I used to use it as a hand-warmer in the lab during the winter. It’s no big freaking deal, and it isn’t gonna spit squat at you. It’s because of people freaking like this that people are afraid of “chemicals”. ---
**Author:** ![Amberlei](https://avatars.discourse-cdn.com/v4/letter/a/e56c9b/32.png) [@Amberlei](https://boards.straightdope.com/u/Amberlei)\ **Post date:** [November 18, 2003, 12:30pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/15 "2003-11-18T12:30:36Z")
[http://sparkychem.wcu.edu/Alum.pdf](http://sparkychem.wcu.edu/Alum.pdf). And just what’s wrong with people being a bit cautious around chemicals? We’re talking concentrated acids and bases here, ya know. They are dangerous if used without proper care. ---
**Author:** ![asterion](https://avatars.discourse-cdn.com/v4/letter/a/4da419/32.png) [@asterion](https://boards.straightdope.com/u/asterion)\ **Post date:** [November 18, 2003, 1:21pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/16 "2003-11-18T13:21:39Z")
> [@](#): > > \*Originally posted by curly chick \* > \*\*Fisher Scientific and VWR are large international laboratory supply houses which sell, among other things, chemicals on line. Rather than attempting to make these things, when you say yourself you know nothing about chemistry, why not just buy them? > I do not know what the chemical name for alum is, but you might find that one of these companies sells alum too. > [Fisher](https://www1.fishersci.com/index.jsp) > [VWR](http://www.vwrsp.com/) \*\* Good luck. I don’t believe any chemical company, be it Fisher or VWR or Aldrich or Argos or any other company you name will sell to an individual who is not connected with either a lab or a school. Not sure if it’s a corporate policy or a federal regulation. ---
**Author:** ![PbZep](https://avatars.discourse-cdn.com/v4/letter/p/58f4c7/32.png) [@PbZep](https://boards.straightdope.com/u/PbZep)\ **Post date:** [November 18, 2003, 3:17pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/17 "2003-11-18T15:17:24Z")
**Squink** said… “You can make aluminum sulfate by pouring sulfuric acid (from the hardware store) over aluminum foil. You’ll have to neutralize any excess acid with, say, potassium hydroxide. It’s easier just to go to the local gardening store and buy a box of aluminum sulfate. It’s used as a soil additive to turn hydrangea blossoms blue.” I read the first part in laymans terms as: Go to the hardware store and buy some battery acid and lye. Dip the aluminum in the acid and after some time has passed, throw in some lye to neutralize it. Anyway, I was just trying to help. Then again, anyone taking instructions for mixing chemicals off the internet probably deserves what they get. ---
**Author:** ![curly\_chick](https://avatars.discourse-cdn.com/v4/letter/c/7ba0ec/32.png) [@curly\_chick](https://boards.straightdope.com/u/curly_chick)\ **Post date:** [November 18, 2003, 3:26pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/18 "2003-11-18T15:26:10Z")
> [@](#): > > \*Originally posted by asterion \* > \*\*Good luck. I don’t believe any chemical company, be it Fisher or VWR or Aldrich or Argos or any other company you name will sell to an individual who is not connected with either a lab or a school. Not sure if it’s a corporate policy or a federal regulation. \*\* I maintain the e-commerce site for a company who do, all the time. As you can see from my location, I am not in the US, as I see you are, and if you say that the rules there are different, then I’ll believe you, as I have no idea. However, I see that **Jojo** spells aluminium, sulphate and sulphuric like I do, rather than in the American fashion, suggesting to me a poster from this side of the pond, where American federal laws hold little sway. Funnily enough. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [November 18, 2003, 4:55pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/19 "2003-11-18T16:55:25Z")
[http://shop.store.yahoo.com/mastergardening/too-2026.html](http://shop.store.yahoo.com/mastergardening/too-2026.html) ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [November 18, 2003, 5:51pm UTC](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740/20 "2003-11-18T17:51:57Z")
Jojo, what are you doing with this stuff, anyway? [Next page](https://boards.straightdope.com/t/chemistry-q-how-do-i-make-aluminium-sulphate/213740.md?page=2)