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Indentify illegal fuel

  1. Dec 5, 2015 #1
    There's has been a report on illegal fuel in my country recently
    This is how they do
    Suppose a fuel truck ( tank ) carrying 900 litres of fuel
    The driver will go to somewhere desolated. He will then take out 40 litres of fuel and add 40 litres of kerosene back. Since fuel is much more expensive than Kerosene, he will then sell the fuel.


    Now is there anyway to indentify if it's a mixture of fuel and kerosene or just fuel
     
  2. jcsd
  3. Dec 6, 2015 #2

    Borek

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    I am afraid there is no simple and safe way of checking.
     
  4. Dec 12, 2015 #3
    kjfunh,

    You never said where you were in the supply chain.

    One way this is attended to in some jurisdictions is to put harmless dye in the various fuels with different tax revenue obligations so that misappropriation will be evident.

    For example: If the retailers or refiners put a purple dye in kerosene before it was sold to the public, there would be clear evidence in the fuel supply system of the driver who made the illegal swap. The diluted fuel would have a purple dye in in, in some easily identifyable proportion to the substitution. This is a way that has been used in the US to combat such activity. Not so much a chemical assay as a simple visual observation easily performed by inspectors.


    diogenesNY
     
  5. Dec 13, 2015 #4
    Woops sorry for that. Assume that I'm going to the gas station and buy some fuel
    Thanks for the reply but I'm afraid that your solution is not pratical in our country to due to the fact that smuggling occurs very often
    And no supplier want to do that ???
     
  6. Dec 13, 2015 #5

    DaveC426913

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    Try an experiment. Mix a quarter litre of kerosene into a litre of gasoline. Leave it to sit, and see how long it takes to separate.

    Kerosene 810 kg/m3
    Gasoline 710-770 kg/m3

    I don't know if there's enough difference to have success, but it can't hurt to try.


    Here's another thread on the subject, though I don't think there's much useful to you in it.
    https://www.physicsforums.com/threads/80-gasoline-20-kerosene-20-more-power.794903/page-2
     
    Last edited: Dec 13, 2015
  7. Dec 13, 2015 #6

    Vanadium 50

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    Dave, why do you think that the ingredients in kerosene and gasoline will mix with themselves but not with each other?
     
  8. Dec 13, 2015 #7

    DaveC426913

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    Not sure that's what I was saying. With Kerosene's density, you should get some stratification if you wait long enough.
     
  9. Dec 13, 2015 #8

    Vanadium 50

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    Kerosene and gasoline are both mixtures of hydrocarbons. Why do you think you will get stratification into those exact mixtures?
     
  10. Dec 13, 2015 #9

    DaveC426913

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    Not exact. I figure they'd be different enough that you'd get Kerosene settling. It's 10% denser.

    But I am merely surmising. I suppose I'm oversimplifying the complex subtlety of hydrocarbon soups.

    I defer to those who are more adept at organic chemistry than I.
     
  11. Dec 14, 2015 #10

    Borek

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    Nothing complicated here. Most hydrocarbons are just miscible, no matter what their density is.
     
  12. Dec 14, 2015 #11
    In any case, I suspect (just this side of a wild guess,mind you) that the OP's referenced fuel that is being diluted with kerosene is not gasoline,but diesel. This is a fairly widespread fraud and the messy mixture can burn serviceablly in a diesel engine, but I wouldn't recommend this practice, for many reasons.

    Kjfunh, where are you located? Commercial fuels and other refined combustibles often have a package of use and condition specific chemicals added to them depending on intended use, region, climate, national regulations, etc. Perhaps evidence of one class of additives in the wrong supply pool could be a guide post. Without knowing the specifics of your location and situation, further conjecture is difficult.

    diogenesNY
     
  13. Dec 20, 2015 #12
    It depends what you mean by "simple and safe".
    GC (or better, GC/MS) would be pretty simple and safe, it would just require equipment that most people don't have around the house.
     
  14. Dec 20, 2015 #13

    Borek

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    Which puts it outside of what I consider simple :wink:
     
  15. Dec 20, 2015 #14

    Vanadium 50

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    Consider salt water. It's denser than freshwater, but you don't see it settling and oceans having freshwater on top.
     
  16. Dec 20, 2015 #15

    DaveC426913

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    The oceans are constantly mixing.
     
  17. Dec 20, 2015 #16

    Vanadium 50

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    OK, I give up. In general, hydrocarbons are miscible and form solutions - i.e. don't stratify the way you claim they will. Indeed, gasoline and kerosene are already solutions. They are even solutions that contain some of the same molecules (although not so many, because there is another commecial mixture, naptha, intermediate between the two). It simply does not work the way you say.
     
  18. Dec 20, 2015 #17

    Merlin3189

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    Do I understand from Va50, that when miscible fluid misc, they stay misced? I'd always thought that and my lay experience seems to support that idea. But I see posts on PF that seem to say that this is the case only if the fluid is continuously stirred. If kept undisturbed, even the gases of the atmosphere would separate.
    In this latter case I do accept that gases like CO2, Butane, Gasoline vapour, etc do pool at the bottom of containers before they become mixed. Though I doubt they will pool by unmixing after they have been mixed. (Tho' perhaps the mixture containing them could also pool relative to air not so contaminated, so long as those two masses of gas remained unmixed. Eventually I would expect diffusion to produce a homogeneous mixture.) I guess that problems with Radon and CO2 may well exist in mines, but I guess that is because these gasses are produced at the bottom of these mines and diffusion is not fast enough to mix them up to the surface: they separate (to any extent that they do) because they have never become more mixed.
     
  19. Dec 20, 2015 #18

    Vanadium 50

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    Consider a bottle of wine - the alcohol doesn't float to the top. Even after years.
     
  20. Dec 21, 2015 #19

    Borek

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    To some extent the separation of different fractions takes place, with those lighter going up and those heavier sinking. This is especially easily observed in the gases and is a basis of a method of separation of a mixture components differing in their molar masses (called cryogenic distillation). However, the process doesn't take place in normal conditions, when the thermal energies of molecules are high enough to provide diffusional mixing (which is why wine mentioned by V50 won't separate). In the case of a fuel the problem is everything will solidify long before the temperature is low enough to allow separation of components. Then, even assuming separation will work, you will separate not kerosene from gasoline, but different hydrocarbons from the mixture. While the exact composition is an information that can be used to find out if the fuel was mixed or not, this is again not something trivial.

    Probably the simplest approach is to measure the fuel density - as the density of gasoline is quite variable it won't catch every case (so it is far from being perfect), but it should catch at least some of the most blatant cases.
     
  21. Dec 21, 2015 #20

    TeethWhitener

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    Since kerosene and gasoline have different densities, it might be possible to simply measure the density of the mystery fuel. The caveat is that the density of a liquid mixture is not always monotonic with respect to the mole fractions of the constituents. But a quick lit search reveals that, at least for light hydrocarbon mixtures, density is monotonic. I would hazard a guess that, since hydrocarbons in general have relatively weak intermolecular forces, the monotonicity trend holds for the heavier hydrocarbons found in kerosene and gasoline. The drawback to this is that both fuels have density ranges, so measuring the density might just give you too fuzzy an answer to make any claims about the fuel's legitimacy.

    Edit: Just saw Borek's reply above mine.
     
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