Dan wrote:
Soil and Dirt particles?! Is that a scientific analysis? Contaminated?
Do you see many pure celulose trees?

Ideally, you should get CO2 and H2O, but nothing's ideal. You don't get
enough Oxygen to get such efficient burning, so, you get a lot of
charcoal (near pure carbon), as well as lots of other stuff like
nitrates and salts that are absorbed from the soil.

We know this because ash used to be the main source of nitrates

I strongly doubt that. Nitrates would not survive high temperatues (of
burning wood) especially in the presence of organic matter. Wood ash is
indeed rich in what we call as
pot-ash and hence the name potassium.

An analysis of Oak/Beech/Bracken tree ash was published Archaeometry
Volume 47 Page 781 - November 2005. The results for Oak tree ash:
%
SiO2- 14.62
TiO2 - 0.06
Al2O3 - 0.76
Fe2O3- 0.65
MnO 6.35
MgO 6.87
CaO 31.06
Na2O 0.40
K2O 18.80
P2O5 12.87
SO3 1.09
Co 15.5
Ni 75.7
Cu 178.5
Zn 2112.4
Ge 3.0
As 1.9
Se 1.3
Br 3.4
Rb 107.9
Sr 533.6
Y 3.0
Zr 41.6
Nb 1.6
Mo 6.5
Ag 1.0
Sn 7.5
Ba 3560.3
Pb 46.1
Th 0.4
U 4.7




You could look at some analytical techniques ot detect levels of such
nitrates and salts, which should be fairly straight forward, but I'm a
chemoinformatician not an analyst....

Happy Ashin'

Dan.