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

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)

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

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.

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

 

let me guess you also got a white ppt too

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

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

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

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

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.