What is ash made of?

Discussion in 'Chemistry' started by Cyperium, Jul 23, 2008.

  1. Cyperium I'm always me Valued Senior Member

    When anything organic burns, it becomes carbon and when the carbon has burnt it becomes ash, so what is ash made of?
  2. Enmos Moderator

    Carbon compounds and all sorts of other stuff originally present in the material.
  3. Cyperium I'm always me Valued Senior Member

    But ash is the leftovers from that which burns, so what other stuff doesn't burn? Is it possible to burn away all the ash?

    Is ash present when burning other things than organical stuff?

    I know that plastics just seems to turn liquid and to smoke.
  4. Enmos Moderator

    "In the large majority of the real world uses of combustion, the oxygen (O2) oxidant is obtained from the ambient air and the resultant flue gas from the combustion will contain nitrogen:

    CH4 + 2O2 + 7.52N2 → CO2 + 2H2O + 7.52N2 + heat

    As can be seen, when air is the source of the oxygen, nitrogen is by far the largest part of the resultant flue gas.

    In reality, combustion processes are never perfect or complete. In flue gases from combustion of carbon (as in coal combustion) or carbon compounds (as in combustion of hydrocarbons, wood etc.) both unburned carbon (as soot) and carbon compounds (CO and others) will be present. Also, when air is the oxidant, some nitrogen will be oxidized to various nitrogen oxides (NOx)."


    Everything that's too heavy to get airborne stays behind as ash. It's largely carbon compounds.
    Mostly it's organics that will produce ash.
  5. Read-Only Valued Senior Member

    It depends, of course, on what the original material was. A common one, wood, also leaves a fair amount of phosphorus and potassium compounds in the ash. ;)
  6. OilIsMastery Banned Banned

    "Organic" means carbon...:rolleyes:

    Therefore anything "organic" that burns was carbon before it was burned.

    Carbon and a bunch of other elements. Duh.
  7. John99 Banned Banned

  8. Enmos Moderator

    Of course (see post 2) ;)
  9. Enmos Moderator


    1. noting or pertaining to a class of chemical compounds that formerly comprised only those existing in or derived from plants or animals, but that now includes all other compounds of carbon.
    2. characteristic of, pertaining to, or derived from living organisms: organic remains found in rocks.
    3. of or pertaining to an organ or the organs of an animal, plant, or fungus.
    4. of, pertaining to, or affecting living tissue: organic pathology.


    1. Chemistry. a widely distributed element that forms organic compounds in combination with hydrogen, oxygen, etc., and that occurs in a pure state as diamond and graphite, and in an impure state as charcoal. Symbol: C; atomic weight: 12.011; atomic number: 6; specific gravity: (of diamond) 3.51 at 20°C; (of graphite) 2.26 at 20°C.

  10. Read-Only Valued Senior Member

    Yep, But I thought it might be of interest to the OP to know what some of the "other stuff" is. ;)
  11. Enmos Moderator

    Fair enough :p
  12. OilIsMastery Banned Banned

    Seriously, borrow a clue.


    Last edited: Jul 24, 2008
  13. Cyperium I'm always me Valued Senior Member

    Yeah, thanks :)

    I just stumbled upon the question when I thought about how fascinating it was that when things burn you can see what it is made of (carbon based) since it doesn't burn as easily :), then I just wondered what all the ash was.

    So the other things are turned into gas (and smoke), but ash are the things that just simply won't burn.

    If you heated it tremendously it would burn though (right?), how tremendously would you need to heat ash for it to burn? - depends on the things in it of course, but generally?
  14. Sciencelovah Registered Senior Member


    Ash is basically a residue resulted from an incomplete combustion. What are ash
    made of is basically depends on:
    1. the element that composed the material that you burn (of course).
    2. the oxygen available for the combustion
    3. the temperature you use for the combustion.

    That is said, if the material composed of organic (including organic carbon)
    and anorganic (including anorganic carbon), and you burn with insufficient
    oxygen, you will likely get the organic carbon, anorganic carbon (carbon in
    anorganic compound) and the rest of the anorganic (minerals) in the ash.
    If you increase the oxygen until it is more than its stoichiometric requirement,
    you can burn all the organic carbon as well. However, if the temperature is
    low enough, you will still get the anorganic carbon and other anorganic /
    minerals in the ash.

    Here is an example of ash composition resulted from combustion of different
    woods and different temperature (600 vs 1300 oC):


    Table source: Misra et. al, 1993, "WOOD ASH COMPOSITION AS A FUNCTION OF FURNACE TEMPERATURE" (pdf).
    Last edited: Jul 25, 2008
  15. Sciencelovah Registered Senior Member

    As an additional note, as Read-Only mentioned before:

    Because ash mostly composed of mineral residue (that is the minerals which
    compose the original material but left unburnt), such as phosphorous (P) and
    potassium (K), such ashes are often used as fertilizer because it contains
    nutrient needed for plant growth (N, P, K, etc). It is also common to use ash
    for potash production, provided the ash contain potash (K) mineral.
  16. Enmos Moderator

    lol COMPOUNDS, not carbon. Carbon is an element, it's NOT organic.

    I used to think you were just a trolling asshole, now I'm starting to think you are just an arrogant dumb shit.
  17. OilIsMastery Banned Banned

    No shit...lol. I know.

    Tell that to vitalists, organic chemists, and biogenic petroleum geologists.

    Good scientific argument. I love ad hominem attacks because they make you look like a moron.
  18. Enmos Moderator

    Then why did you say Carbon = organic ?

    Now you know why I call you one.
  19. OilIsMastery Banned Banned

    I don't say that; vitalists, organic chemists, and biogenic petroleum geologists say that.
  20. Enmos Moderator

    Then what is this:

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