FGP - 12-1-2004 at 03:25
Before synthetic alkali carbonates became available early chemists suggested that potash could be made by reacting saltpetre with carbon. We would now
write:
2KNO3 + 3C = K2CO3 + CO2 +CO +N2.
What would be the best conditions to get this reaction going? Is it likely to get out of hand?
Mr. Wizard - 12-1-2004 at 09:42
Potash was made by soaking wood ash in water and letting the non solubles settle out. It can still be made that way. Get some ash from your fireplace,
put it in a 5 gallon bucket full of water, stir it well and let it sit. In a few days the clear liquid on the top can be siphoned off and dried to
yield potassium carbonate. (potash) The ash can be mixed with more water and the process repeated until yield fall. this is not a pure product, but
it can be purified by recrystalization and filtering.
Coal ash may not work. Barbeque briquet ash is mostly clay used to bind the briquettes. different woods have varying impurities such as salt, lime,
sand, and God knows what else.
Filters would also work, but they would be bulky. Gravity will do the work if you are not in a hurry. Potassium is named after this source of it. The
name Kalium was the source for the K symbol of potassium, and I believe it still is the name in some European countries. Perhaps some of our friends
in Europe can help me on this.
Theoretic - 12-1-2004 at 11:20
Mr. Wizard:
See my post at "User names and boredom..." in Whimsy.
vulture - 12-1-2004 at 12:25
You will get very little K2CO3 as what you describe is basically sulfurless blackpowder.
blip - 12-1-2004 at 15:02
I tried that at my grandmother's house last summer and the dirt and dust impurities still haven't settled. I think it was there so long
that it could have formed potassium bicarbonate as well, because even the really raw stuff practically exploded upon addition of HCl. I know that
fireplace was used for many, many years because I found tiny scraps of unburnt pieces of newspapers and catalogs from around the '50s and
'60s. It's not like I don't have a good bicarbonate source already, but it'd be nice to have nearly as much I started with (two
cat litter containers full). I'm thinking that over time this occurred to the K<sub>2</sub>CO<sub>3</sub> as
CO<sub>2</sub> and H<sub>2</sub>O reacted with it, with the latter two acting as carbonic acid:
K<sub>2</sub>CO<sub>3</sub> + CO<sub>2</sub> + H<sub>2</sub>O <sup><u> <style
type="text/css">a:link{text-decoration: underline;}a:visited{text-decoration: underline;}a:hover{text-decoration:
underline;}a:active{text-decoration: underline;}</style><a
href="http://www.armandproducts.com/pdfs/PotassiumBicarbonateAnhydrousAllGrades.pdf" target="_blank">below
212°F-392°F</a></u></sup><s> ></s> 2KHCO<sub>3</sub>
Mumbles - 12-1-2004 at 16:55
There was a reaction similar to that that produces cyanide. Not something you'd want to mix up if neutralising acid. Theres yet another similar
one to make KNO2 I believe. Also not pleasant to neutralise with.
Hermes_Trismegistus - 17-1-2004 at 23:35
Are you certain? I remember using ash water as a potassium source for plants and it hard to use because it would burn the plants so, so easily. I
remember reading it was because the main soluble component was Potassium Hydroxide?
unionised - 18-1-2004 at 05:21
if the hydroxide were made by the fire it would form the carbonate in the presence of all the CO2 from the fire. It' carbonate that you get from
leaching ashes. It's still very alkaline.
KOH and Potash
Mr. Wizard - 18-1-2004 at 10:28
unionised is right about the Carbonate forming from ash over the hydroxide or oxide. All is not lost though if you really want the KOH. Mix slaked
lime, the ordinary mason's lime, with the ashes and you will get KOH after the resulting CaCO3 precipitates. You can do this afterwards for a
more pure product, but it adds another step. You will also get the dissolved CaOH unless you keep the K2CO3 in excess. I do concede this will be a
messy sloppy dirty process, with a lot of work with little product. The KOH solution will be short lived if it is exposed to the CO2 of the air. The
KHCO3 formed by exposure to the air is supposed to decompose in the 100c to 200c range, giving the carbonate. This would rival making your own
soap,lime, charcoal, nitre, and alcohol. What fun ;-)