View Full Version : pottasium nitrate

December 18, 2009, 06:21 AM
Hi All .Does anyone out there know what the correct composition of pottasium nitrate should be? The stuff im getting is Nitrogen-13%,Potassium Oxide-46.2% and Potassium-38% .Chlorides0.17%. This seems to go alright but I think I could do better.Im using British Willow airfloat charcoal and 99,8% pure Sulphur. I mix standard ratio 75-15-10 using a mortar and pestle.If I corn it, wet through a strainer its dynamite, but as an ultrafine meal powder it seems to lose something.When its corned to look like instant coffee,you cant light a pile in an ashtray with a cigarette lighter without burning your hand.When I grind it to an absolute dust and sift it through a cloth it just seems to fizzle a bit:confused:Any ideas THANKS Sam

Shotgun Willy
December 18, 2009, 02:15 PM
You're using fertilizer, not potassium nitrate. Pot. nitrate is KNO3, and is not a fertilizer. Look for stump killer.

Mike Irwin
December 18, 2009, 02:33 PM
Just get the right kind of stump killer.

There are several formulas on the market.

Potassium nitrate stump killer makes great smoke bombs.

The stuff I bought a couple of years ago? Horrific stink but no smoke when we tried to make smoke bombs.

December 18, 2009, 03:55 PM
.....Actually potassium nitrate IS a very good fertilizer. Most fertilizers are NOT potassium nitrate, even if they contain SOME KNO3.

December 18, 2009, 07:33 PM
The correct composition of potassium nitrate is one molecule of Potassium, one molecule of Nitrogen, and three molecules of Oxygen. The stuff described in the opening post is not KNO3, but they do sell KNO3 as fertilizer and if you can find it, it is higher quality KNO3, than stump remover.

I talked to a guy that said this aquarium fertilizer (http://www.aquariumfertilizer.com/index.asp?Option1=inven&EditU=2&Regit=12&ReturnOption1=new&ReturnEdit=&Returnitemname=&ReturnShowItemStart=) is pretty good stuff!

December 18, 2009, 09:13 PM
Potassium nitrate is also called saltpeter. It used to be sold in the spice rack of grocery stores for curing sausage. Maybe it still is in places where people do a lot of their own sausage making.

I have also seen it sold in the drug isle.

Jim Watson
December 18, 2009, 09:26 PM
Pure potassium nitrate, KNO3, is 13.8% nitrogen, 38.7% potssium (expressed for fertilizer as 46% K2O), so your stuff is somewhere between 94 and 98% pure depending on how they rounded off the actual analysis. That seems to be doing ok based on your description of how it behaves in corned gunpowder. I dunno about the pulverized stuff and don't see why it matters.

There is a brand of stump remover advertised at 99.8% KNO3 on eBay and a fertilizer advertised at 98.6%, which seems very pure considering that technical grade is only required to be 98+%.

Oh, by the way, guys, potassium nitrate is an excellent fertilizer but too expensive for wide use except in particular applications where the usual potassium source of potassium chloride is toxic to some crops like tobacco or where it is desirable to minimize the salt index.

December 19, 2009, 05:32 AM
The KNO3 im buying is labelled as 99.5 % pure . The analysis sheet that comes with it says N=13% K2O=46.2% K=38% Just wondering if there are any chemist types out there who could confirm its purity? THANKS ALL Sam

Jim Watson
December 19, 2009, 09:26 AM
How can a chemist "confirm its purity" without having it in hand to do a chemical analysis? There is not much you can do but trust the label or not. It would be cheaper to buy a different brand than pay for analyis. I used to work in fertilizer R&D engineering and was always at the mercy of the analytical laboratory.

December 19, 2009, 10:27 AM
"K2O" is potassium oxide which becomes two molecules of potassium hydroxide KOH (lye) the first time it meets a water molecule.
Potassium nitrate is simply potassium nitrate. It does not contain any K20.

December 19, 2009, 10:40 AM
The stuff you bought should be reasonably pure potassium nitrate, based on those numbers. They just have a weird way of expressing it when labelling fertilizer. Where'd you find the stuff?

Jim Watson
December 19, 2009, 11:44 AM
Potassium nitrate is simply potassium nitrate. It does not contain any K20.

It doesn't CONTAIN any K2O but due to old analytical methods taken as reference points for a century or so, the potassium content of fertilizer is EXPRESSED in terms of equivalent K2O level.

Just as the phosphate content of fertilizer is figured as though it were P2O5 and not elemental phosphorus. Unless you are talking about phosphoric acid which is usually given in terms of H3PO4 even when it is at "superphosphoric acid" concentrations and you get numbers like 105% acid.

December 20, 2009, 06:53 AM
Its OK. I was expecting my homemade BP to burn down a touch hole only 5/64" dia .:o It will sometimes but more often not. I have to spend some more time over the old mortar and pestle cos I know that makes it all go better.

Derek Rose
December 20, 2009, 03:03 PM
I think it needs to be washed through with alcohol