Sciencemadness Discussion Board

Wood ashes

nscheffield - 10-2-2016 at 06:53

So i am trying to determine what is in wood ash. I understand there is calcium, potassium, magnesium, and sodium carbonates/oxides. What i have done so far is burn a large amount of wood and collected the ashes, removed the majority of charcoal bits (there is a few flecks left but not enough to matter that much) i also soaked the ashes in distilled water, with occasional stirring, filtered and repeated. after doing that 3 times i washed the ashes with dilute acetic acid, definitely so CO2 released. Did this twice then dried the ashes. I evaporated the wash water (both from distilled water and dilute acetic acid) i was left with a mix of compounds.
Now my problem is i am left with this gray, powdered sugar like stuff. it isn't water soluble, it doesn't burn, doesn't react with dilute acids, so i am quite frankly confused at what it could be. I am pretty sure what ever it was was at one point water soluble, other wise it wouldn't have gotten into the tree.

I live in the north east USA. The ground here is high in clay, acidic, and contains higher levels of uranium than most parts of the country. (uranium is from the natural deposits under the state) The trees were at least 90-150 years old. (they had started to rot at the top, had to be cut down)

Detonationology - 10-2-2016 at 07:06

What size filter did you use? Did the filtrate appear to be relatively clear upon filtering?

Praxichys - 10-2-2016 at 07:25

In the first few distilled water washes you are likely to find hydroxides and carbonates of sodium and potassium, along with some phosphates.

The acid wash will have removed calcium and magnesium carbonates/hydroxides as the acetate salts.

I'm going to take a wild guess that the bulk of what's left is probably aluminosilicates/K, Na, Ca-silicate/carbonate glass with traces of transition metal oxides.

[Edited on 10-2-2016 by Praxichys]

nscheffield - 10-2-2016 at 09:17

the paper had a pore size of 2 µm, how ever i used a cheap coffee filter first to get the majority of the larger stuff out.
the filtrate that came out was clear, granted it had a slight color to it but no noticeable particles or cloudy-ness.

it just seems odd that the majority of the ash is aluminosilicates/K, Na, Ca-silicate/carbonate glass. The mass of what i leached out was not even 10% by weight of the starting ashes. I am no expert in this particular field so if this is in fact what it is ill take your word for it.

thanks for your guys input

arkoma - 10-2-2016 at 10:06

I've been burning Pecan and Red Oak here in rural SW Arkansas and leaching the ashes. Been getting fairly high quality K2CO3 with rudimentary filtration and two recrystallizations.

nscheffield - 10-2-2016 at 10:17

I just have a habit of wanting to not waste any possible chemical reagent. I keep everything that could possibly be used. Urine for the urea and salt, pieces of metal (nails from junk fires, soda bottle caps, broken electronic) for iron/copper/zinc/ etc, even the gasses produced from my compost bin (for ammonia, methane, and hydrogen sulfide)
so not knowing what was left over after leaching bugged the heck out of me. now i need to find a use for aluminosilicates/K, Na, Ca-silicate/carbonate glass

MeshPL - 12-2-2016 at 10:18

Plant ashes contain phosphorus in form of oxide, but are not very rich in sodium.

Random - 12-2-2016 at 11:24

Quote: Originally posted by MeshPL  
Plant ashes contain phosphorus in form of oxide, but are not very rich in sodium.


I don't think so

Detonationology - 12-2-2016 at 11:28

Phosphorus oxides? Not likely. Perhaps you meant to say phosphates (PO4)?

[Edited on 2-12-2016 by Detonationology]

Texium - 12-2-2016 at 11:35

Somehow I find it doubtful that there would be any phosphorus pentoxide present in wood ashes. If any was formed in the heat of the fire at all, it would absorb water from the atmosphere on cooling forming phosphoric acid which would react with with the alkaline components of the ash to form phosphates.

DraconicAcid - 12-2-2016 at 11:46

Quote: Originally posted by zts16  
Somehow I find it doubtful that there would be any phosphorus pentoxide present in wood ashes. If any was formed in the heat of the fire at all, it would absorb water from the atmosphere on cooling forming phosphoric acid which would react with with the alkaline components of the ash to form phosphates.


I'm sure it would be in the form of phosphates. However, fertilizers often claim that they contain such-and-such a mass of phosphorus as P2O5, even though it's as a phosphate. It comes from a very old way of looking at such compounds, like writing sodium carbonate as Na2O*CO2.

MeshPL - 13-2-2016 at 04:50

Yes I meant "phosphorus oxide", but the same way as it is present in phosphate fertilisers, I should have written phosphates, as that would be a more correct and unambiguous way of saying that. Ashes also contain magnesium in form of oxide and salts.

feacetech - 14-2-2016 at 16:17

Quote: Originally posted by DraconicAcid  

I'm sure it would be in the form of phosphates. However, fertilizers often claim that they contain such-and-such a mass of phosphorus as P2O5, even though it's as a phosphate. It comes from a very old way of looking at such compounds, like writing sodium carbonate as Na2O*CO2.


Its just a way of expressing the elemental composition in a fertiliser.

Total P as P2O5 or BPL or Just plain P

just a little bit of math trickery i.e. if I had X% P if I assume its in its oxide I can assume I have Y% of P2O5 (%P x 2.29136 (molar mass P2O5 / 2x molar mass P))

Its a very common mathematical manipulation in chemistry as well as a way to trick you into thinking you are getting more!

Amos - 14-2-2016 at 20:58

My guess would be calcium and magnesium phosphate, some sulfate, and quite likely oxides or hydroxides that were too calcined and unreactive from the high temperature of the fire to react quickly with dilute acetic acid.

nscheffield - 16-2-2016 at 11:28

Would a stronger acid help to remove some of the above mentioned compounds?