Sciencemadness Discussion Board

Not really iron?

hodges - 7-1-2023 at 08:16

I bought some iron filings in order to make iron sulfide.

I heated stoichiometric amounts of this and fine (sublimed) sulfur in a test tube using a torch. No reaction. I even heated part of the test tube until it glowed orange. Melted all the sulfur until it boiled. Still did not ignite, and still as magnetic as it was originally.

I'm wondering if this might not really be iron filings? Maybe it is magnetite? Or perhaps the particle size is too large to react?


IMG_3355.JPG - 2.9MB

clearly_not_atara - 7-1-2023 at 13:38

Remember that story about Archimedes and the crown?

DraconicAcid - 7-1-2023 at 15:04

I find that reaction rarely works, even with proper iron.

Sulaiman - 7-1-2023 at 15:24

Fine iron powder rusts easily/quickly in humid air.
Iron powder should look silver to grey colour.
If your sample looks brownish then the surface has oxidised,
which makes initiation of the reaction difficult.

Try direct application of a flame to the mixture.

It is possible that ALL of the iron has rusted in which case I doubt that the reaction will work.

I can't think of anything cheaper than iron that is attracted to a magnet so its unlikely to be fake.

This reaction has always worked for me.

Assuming that you intend making H2S, don't underestimate its toxicity

Sir_Gawain - 7-1-2023 at 15:55

How fine are the filings? This reaction won't work with coarse iron filings; you'll need a fine powder.

Rainwater - 8-1-2023 at 09:58

You can always mix some with carbon and reduce it back to iron

blogfast25 - 8-1-2023 at 11:07

Quote: Originally posted by Rainwater  
You can always mix some with carbon and reduce it back to iron


If only it was as simple as you make it sound. It's a process that requires high temperatures.

I'd say buy a better grade, perhaps from a reputable chemsupplier?


[Edited on 8-1-2023 by blogfast25]

hodges - 8-1-2023 at 12:20

Quote: Originally posted by Sir_Gawain  
How fine are the filings? This reaction won't work with coarse iron filings; you'll need a fine powder.


As you can see from the picture, they are fairly course. Maybe that is the problem?

DraconicAcid - 8-1-2023 at 12:21

Quote: Originally posted by hodges  
Quote: Originally posted by Sir_Gawain  
How fine are the filings? This reaction won't work with coarse iron filings; you'll need a fine powder.


As you can see from the picture, they are fairly course. Maybe that is the problem?


Yes, and possibly oxidized at the surface, too.

Sulaiman - 8-1-2023 at 19:48

If test tube scale does not work,
I would try ;
1 get a clean dry tin can
2 lightly grind some of the iron filings to expose the un-oxidised iron,
You can use a mortar and pestle or a blender etc.
3 put a weighed quantity (eg 50g) of the iron into the tin
4 add powdered sulfur (about 1.5x the weight of iron = excess) to the iron in the tin
5 mix well
6 outdoors, throw a burning match into the mix
7 if that does not work use Mg strip or a firework sparkler.

The result will be usable for H2S production

Sulaiman - 12-1-2023 at 07:42

P.S. A convenient source of small quantities of very fine iron powder is in dessicant packets as found with food items.
The sachets look similar to the previously more common silica gel dessicant packs.
Easy to identify with a magnet.
I expect the iron to be free of toxic elements or compounds, (food grade)
but I do no know its purity.

Larger quantities of iron powder are used in single-use heating pads,
I forget if this source is a fine powder or not,
and it would not need to be food grade.

Used dessicant or heating packs would of course contain Fe2O3.

hodges - 12-1-2023 at 15:19

Quote: Originally posted by Sulaiman  
P.S. A convenient source of small quantities of very fine iron powder is in dessicant packets as found with food items.
The sachets look similar to the previously more common silica gel dessicant packs.
Easy to identify with a magnet.
I expect the iron to be free of toxic elements or compounds, (food grade)
but I do no know its purity.

Larger quantities of iron powder are used in single-use heating pads,
I forget if this source is a fine powder or not,
and it would not need to be food grade.

Used dessicant or heating packs would of course contain Fe2O3.


Interesting! I assumed these were always silica gel. I will test with a magnet next time. Beef jerky packages for example.

hodges - 12-1-2023 at 15:24

I bought some 200 mesh "reduced iron" powder. It is very fine, and shiny.

I was able to get the reaction to work in a test tube, but it took very intense heating to get it started. Upon breaking the test tube, the product is difficult to separate because it sticks to the broken glass.

It is still slightly magnetic, despite the fact that I used a slight excess of sulfur. But I'm sure it is technical grade FeS.