Aluminum Potassium Sulfate

[dubois928]

Got a lot of it from an old chemistry set. I read somewhere that it hydrolyzes in water to form a dilute sulfuric acid. Is this true? I have tried it in a small amount of water, heating and mixing along the way. I have it stored for now, but not sure if it worked.

 

Thanks,

Ken

[Darkblade48]

I don't think solution of alum hydrolyze to form dilute sulfuric acid; this would be like saying that copper sulfate hydrolyzed to form dilute sulfuric acid (which does not occur)

[dubois928]

Well when I came back to the solution it had formed clear crystals in the bottom of the container that stuck there when I poured the solution out to filter it. I scraped the crystals out and set them aside to dry. I then tried to see if the solution would react with sodium bicarbonate, as sulfuric acid does. It did bubble strongly for a moment then tapered off (I didn't use that much at all). So it seems to be sulfuric acid, at least a diluted one. Any thoughts?

 

Ken

[Darkblade48]

Just because a solution bubbles when sodium bicarbonate is added to it does not indicate that sulfuric acid is present.

 

I could add sodium bicarbonate to a solution of copper sulfate and observe a similar bubbling phenomenon.

[YT2095]

it happens because the Sodium cation is more electro Positive than the Alu.

 

let me guess you also got a white ppt too

[dubois928]

So then what is it? Just a simple solution?

I did find where it mentions that it hydrolyzes to form sulfuric acid:

 

http://www.jtbaker.com/msds/englishhtml/a2856.htm

 

"This material hydrolyzes in water to form sulfuric acid, which is responsible for the irritating effects given below."

 

Ken

[Darkblade48]

That might occur when you heat it to, or above, the decomposition temperature; however, that is unlikely to occur at normal STP.

[dubois928]

You mean while I was dissolving the chemical in the water? I did have a pretty hot torch flame I was using to help dissolve it; I would heat it until just before it started to boil then remove the flame. But the reaction with the sodium bicarbonate happened at STP.

 

Ken

[dubois928]

Sorry for the double post, but I'd really like to know if what I made really is a dilute sulfuric acid, or what tests I might do to see if it is.

 

Thanks,

Kenneth Anderson

[Fable]

heat it up and smell it (no, dont do that). dont smell it but see if its turning into thick liquid after losing a lot of water.