KNO3 changing color after being ballmilled?

[Ubehage]

I have taken my new ballmill to good use, and spent most of yesterday grinding KNO3, and sifting it through a 120#.

 

Last night, I set the ballmill to run, and forgot all about it. I realized it, when I got home today and saw the still-running mill.

Well, no problem. It just means that the KNO3 has been fully ground, right?

 

It has, indeed. But it has also changed color

Is that normal?

http://i.imgur.com/gbj00RF.jpg

[rogeryermaw]

If you use lead media then a bit of grey may not be completely out of the question but that looks unusual. Set up details?

[Ubehage]

If you use lead media then a bit of grey may not be completely out of the question but that looks unusual. Set up details?

A brand-new Lortone ballmill, Q33.

Antimony-hardened lead media, also brand-new.

 

There might have been minute traces of sulfur with the KNO3. But we're talking less than half a gram, to 750g of KNO3.

Edited September 8, 2015 by Ubehage

[Oinikis]

It might be that you've ground something colorful in the ballmill before milling the nitrate, and didn't clean it, because, who does that. When I grind the nitrate in my ballmill, it always turns a bit grayish, due to all the BP traces inside, but I don't think it really has an effect on performance, just make sure, no chemicals which form untable mixutures (like KClO3 and sulfur) come in contact.

[Ubehage]

It might be that you've ground something colorful in the ballmill before milling the nitrate, and didn't clean it, because, who does that. When I grind the nitrate in my ballmill, it always turns a bit grayish, due to all the BP traces inside, but I don't think it really has an effect on performance, just make sure, no chemicals which form untable mixutures (like KClO3 and sulfur) come in contact.

Thank you, I am well aware of this.

I intend to get several barrells, and mark them to be used for just 1 thing.

 

But this is brand-new. Only chemicals in there, was the KNO3 that I ground earlier. And it's all from the same batch that I weighed out before getting started.

[stix]

Maybe some sort of heat reaction on the second pass because it was left running, some impurities in the sleeve made their way into the mix.

 

You did say (and have shown in the pic) that the first grind was all good. It will settle after time.

 

Cheers.

[Andres1511]

I got exactly the same thing !

I found out it was rust coming from my media (hardened chrome balls).

Because KNO₃ is an oxidizer, my media oxidized really quickly.

When ballmilling my potassium nitrate, it changed color just like yours did.

It isn't a problem, it works just the same. For Rcandy it even comes in handy, because you don't need to add as much iron oxide as catalyst .

Edited September 9, 2015 by Andres1511

[Ubehage]

I got exactly the same thing !

I found out it was rust coming from my media (hardened chrome balls).

Because KNO₃ is an oxidizer, myoxidized really quickly.

When ballmilling my potassium nitrate, it changed color just like yours did.

It isn't a problem, it works just the same. For Rcandy it even comes in handy, because you don't need to add as much iron oxide as catalyst .

Thank you!

[schroedinger]

Wel, since you didn't use chrome steel balls ironoxide is not very likely. I would rather think that it is a little bit of lead and a little bit of barrel stuff that came lose (propably mostly dust from the production).

[FloridaCracker]

I'm actually surprised it's not more grey than that since you used lead and let it run for so long.

 

My white chemicals are a very obvious grey after just a couple hours. But that is with home made water quenched wheel weight media. If yours was made with a lot of antimony and quite hard I guess that is the difference, and fairly impressive.

 

Sometimes the size of the particle can change the color a few shades with some chemicals. I imagine because the particle size reflects light a little different. But I would still bet on the lead as the cause in this case.