How is it possible to tell if fuel (gas) is contaminated (by water / alcohols / oils etc)?
GCMS - Gas Chromatography with Mass spectroscopy - a 3min job with a volatile and modern equipment.
Is there a simpler way, using something portable?
What is gas but just refined oil with perhaps a few additives?
How badly do you want to know? To what degree of complication are you will to perform tests and with what measurement devices do you have at your disposal?
A density test might reveal something. Gasoline and water have two very different densities (and will not normally mix), as do gasoline and alcohol.
Comparing the heat released by burning the unknown mixture might also be revealing as if the gasoline is mixed with water, a significant chunk of its mass with release no energy when burn...the water will only evaporate away (an endothermic process) and the gasoline combusts (exothermic).
Trying to dissolve things in the mixture might also be a way to tell qualitatively is something is unusual about it.
I'm wih mrjeffy, density would be a dead giveaway for an easy, practical indicator.
dry it with a drying agent. if it starts to clump at all there is water.
I really would like to know. I have no measurement tools at my disposal although I can get access. I would prefer a way that does not involve combusting the fuel.
Can you suggest such a drying agent?
If you have no measurement tools at your disposal then that makes finding out rather difficult.
I would suggest going with the density test. It will be the easiest to perform and will not require many tools (just something [graduated cylinder] to measure out a volume and a [digital] scale to take the mass).
You could probably use something like Calcium Chloride as a drying agent to absorb any water which might be in the fuel.
One can add small amounts of IPA to fuel and it will absorb the water while minimally affecting combustion. That is if you are only concerned about removing any potential water from the fuel. It will not tell you if there is water in the fuel.
contamination by oil - drop of fuel dries out to leave oily residue. good gasoline control sample to compare, of course.
contamination by water - How many layers? two? probably water if there are two. Opalescent fuel not crystal clear? Filter through thick paper filter. water will swell fibers and REALLY slow down filtration rate. Graven-w's dessicant could be anhydrous sodium sulfate or anhydrous magnesium sulfate. Powder is best for clumping observation.
Contamination by alcohols - who cares? It will burn. (Think gasahol) Alcohol is too hard to determine without some kind of distillation equipment (Fractional column, Gas chromatograph, etc...).
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