Mystery of the creeping crystals??

[scmhogg]

A couple of weeks ago, I dissolved some potassium nitrate in water, to do a "fire writing".

This is where you take the liquid and write something in cursive on paper. When it drys, you can touch a cigarette to the end, and it will slowly burn through, and show your message. I had something romantic for LOML in mind.

Anyway, I left the rest of the solution, in a little shot glass sized plastic cup. There was some solid left in less than an inch of water. I used extra powder to make the solution as saturated as possible. Yesterday, I looked at the cup. All of the liquid had evaporated. And the crystals had crept up the side of the cup, and most of the way down the outside.

Anyone know how that happens?





Steve

[Capstone]

I'm not sure but looks like a great idea for a future science project for one of my kids.

Did the fire writing work?

[radhak]

I'm not sure but looks like a great idea for a future science project for one of my kids.

Did the fire writing work?

Ditto, and ditto !

Where do you get potassium nitrate?

[dbhost]

Potassium Nitrate is also known as saltpeter, and there are several recipes for making it online, it used to be available in kids science chemistry sets (which I would assume are LONG gone now due to safety concerns for the younguns... ). I am sure medical supply shops would have it, as may feed stores.

Reading up on the chemical compound, it appears that potassium nitrate will migrate along electrical paths, and follow things such as static electricity. The OP mentioned that this was a plastic cup, perhaps the plastic was static loaded and positively charged? This would explain why the compound migrated around the cup...

[jdon]

Nitrates tend to be pretty hygroscopic (they'll absorb water like crazy, even water vapor in the air). [why lawn fertilizer stored for long periods tends to clump]

I speculate that the potassium nitrate absorbed enough water vapor to dissolve; and there was enough surface tension from the water to "creep" a bit up the side of the container. The crystals then dried "high and dry", but with repeated cycles of absorbing and drying, the crystalline edge moved higher and higher.

Just speculation...

[scmhogg]

Yes, the fire writing did work.

I got the potassium nitrate, food grade, on ebay. I add 1/4 teaspoon, to my salt and sugar cure, that I use to make bacon. Supposed to prevent botulism.

Steve

[JR]

Supposed to prevent botulism.

Thank God! That's a problem I've been trying to solve for a very long time!





JR

[LCHIEN]

Thank God! That's a problem I've been trying to solve for a very long time!





JR

mt botulism preventative measures have been working for almost 60 years when i first started using them. I haven't got it yet.