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Author: Subject: Does 2Al + 3S > Al2S3 Produce Gas?
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[*] posted on 11-7-2011 at 21:08
Does 2Al + 3S > Al2S3 Produce Gas?


I was discussing this thermite with a friend and I stated that this reaction cannot possibly be producing any gas. The only gas that could be produced is from impurities in the mix or a incorrect ratio.

The proper balanced ratio for this reaction is 2/3 Al/S by weight, correct?

It doesn't appear to produce any gas or flame when I burn it.
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[*] posted on 11-7-2011 at 21:23


Such mixtures produce gas only in the initial phases of burning, when the substance undergoing reaction is hot enough to vapourise the products of reaction. When the vapourised products cool, they chrystalize in the form of "smoke" in the air or deposit on some surface.

Conclusions: mixtures like KClO4/Al will burst a steel pipe but will not make a good rocket fuel.




When logic and proportion have fallen sloppy dead...
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[*] posted on 11-7-2011 at 22:12


Sulfur is vaporized at temperatures below 500C, so it seems like some would likely turn to gas; but how much actually escaped would depend on a lot of factors.

Quote:
The proper balanced ratio for this reaction is 2/3 Al/S by weight, correct?


Based purely on stoichiometry we would expect a slightly different ratio. Since the ratio of atoms is 2:3 and the atomic weights are 27 and 32 respectively, an idealized ratio would be 54:96 which is to say 9:16. However, it's entirely possible that slight deviations from this would provide better practical results for one reason or another. In particular, a slight excess of aluminum (which a 2:3 ratio provides) could result in less outgassing of sulfur and/or less formation of sulfur oxides as a result of reaction with the air.
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[*] posted on 11-7-2011 at 22:51


Some S2 gas but also some H2S if moisture is present on the surface of the sulfur (via traces of H2SO4) or on the surface of the aluminium via hydroxyde/oxyde layer.

Note that aluminium sulfide is a strong H2S generator because it is unstable when submitted to water or to air humidity, so beware of the stinky and very poisonous gas.
Al2S3(s) + H2O(l/g) ==> Al(OH)3(s) + 3 H2S(g)




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[*] posted on 18-9-2011 at 22:13


Am i able to make Aluminum Sulfide by wrapping sulfur in aluminum foil and then setting it alight or do i need to powder the aluminum?



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[*] posted on 19-9-2011 at 04:41


If you set it alight (in the open air), various oxides of sulfur and aluminum will be produced and might well predominate, though I'm sure the mess would contain some sulfide as well. I don't know whether the aluminum really needs to be powdered, but it would help make the reaction self-sustaining in the absence of air, which would help - i.e. you could set it alight in a steel can with a small hole in the lid (for vapors to escape), closing the lid after starting the reaction.
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[*] posted on 19-9-2011 at 07:32


Get a rock tumbler and steel marbles and pulverise the aluminum foil (shred it first) for a week or so until it is powdered/granulated. I tried making Al<sub>2</sub>S<sub>3</sub> with it, with success.
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[*] posted on 19-9-2011 at 07:47


Quote: Originally posted by barley81  
Get a rock tumbler and steel marbles and pulverise the aluminum foil (shred it first) for a week or so until it is powdered/granulated. I tried making Al<sub>2</sub>S<sub>3</sub> with it, with success.


Would a coffee grinder do the same as a rock tumbler? im looking to buy a coffee grinder for the sole reason for making aluminum powder




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[*] posted on 19-9-2011 at 09:57


You can also empty out an old Etch-a-Sketch for some very fine aluminum particulate :)
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[*] posted on 19-9-2011 at 11:58


Quote:

Would a coffee grinder do the same as a rock tumbler? im looking to buy a coffee grinder for the sole reason for making aluminum powder

I tried it once, you need to shred the foil by hand first. It just scratched up my coffee grinder and made some little bits of aluminum (not powder, rough granules). I didn't want to let it run very long for the sake of my coffee grinder. Maybe if you let it run for a while you could sift the fine stuff out.

On instructables there is a tutorial, "make german dark aluminum powder" or something like that. It says to add charcoal powder to the aluminum, that makes it more reactive (no oxide layer). It takes about a week for some pretty fine powder.

If you want stearin free etch-a-sketch Al powder, you may suspend it in acetone, let it settle, decant, and dry (or something like that)
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[*] posted on 20-9-2011 at 04:33


was your coffee grider for the sole purpose for making aluminum powder or was it for coffee?



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[*] posted on 20-9-2011 at 07:24


We had discussed Al powder some time back and some very workable ideas were put up.
Sourcing was via the cheapest Al foil available due to it's not having any plastic coating. I had personally tried some techniques to determine if they were not only viable but would not harm any appliances. Most techniques were fine. However if you are considering the reduction in size of an aluminum particulate "steps" or stages" are really mandatory. There are some issues with ball milling aside from just oxidation of the material. Lead will contaminate and steel may spark. Additionally using a kitchen blender to reduce size initially does not appear to stain on a permanent basis if the container is glass.
There was a great deal of discussion of the various attempts back about 2 years ago; some of the attempts did get to a very workable particulate but the use of stearic acid appears to be a very significant step (aside from the oxidation issue) as a plateau appears at about 60 mesh.

The "Etch-a-Sketch" idea is very workable but one issue is the value of the toy as-is vs the value of the product (some people collect old toys). :P

[Edited on 20-9-2011 by quicksilver]




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[*] posted on 25-9-2011 at 04:19


Aluminium sulfide outgasses hydrogen sulfide gas when exposed to air. On top of that, aluminium sulfide is hard as a rock, grinding it is mission impossible. Just dunk it in water and burn the H2S that results. Just be careful.
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[*] posted on 25-9-2011 at 05:05


yeah i wanted to make some easy H2S and use Lead Acetate to test for it, i need a blow torch to ignight the mixture tho so needs to wait :/



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