Sciencemadness Discussion Board - H2S preparation

H2S preparation

Derek McOlund - 10-12-2016 at 12:36

Hi, I need some hydrogen sulfide to make manganese sulfide. What's the best (cheapest and easiest) approach without using any strong acid?

Boffis - 10-12-2016 at 13:17

The tradition method is to heat sulphur and paraffin wax. Fused iron sulphide reacts even with very dilute HCl and H2SO4.

ave369 - 10-12-2016 at 13:30

Be careful with this gas. It's a killer. If you suddenly stop smelling it, turn everything off and run for fresh air!

Sulaiman - 10-12-2016 at 14:28

as a teenager I made a lot of iron sulphide using iron and sulfur powders, as learned in school,
e.g. https://www.youtube.com/watch?v=NxAeQneITNA

but this sounds better
https://www.youtube.com/watch?v=g7v9NYQIQ8k

I have watched videos of H₂S dangers in the petrochemical industry - super scary
but based on my earlier amateur stupidity
- the intolerability of the smell will keep you safe from the gas
but not necessarily from irate neighbours

[Edited on 10-12-2016 by Sulaiman]

[Edited on 10-12-2016 by Sulaiman]

DDTea - 10-12-2016 at 15:04

Quote: Originally posted by Sulaiman

I have watched videos of H₂S dangers in the petrochemical industry - super scary
but based on my earlier amateur stupidity
- the intolerability of the smell will keep you safe from the gas
but not necessarily from irate neighbours

H2S does have a potent, characteristic odor at low concentrations. Unfortunately, at high (dangerous) concentrations, it is odorless. I suspect the receptors responsible for olfaction become saturated and inhibited--they are metal based, after all: http://pubs.acs.org/doi/abs/10.1021/jacs.6b06983 .

Hemoglobin is also metal based and may be inhibited by H2S. Be safe when working with this stuff.

Make sure to use appropriate ventilation / scrubbers for your setup to capture fugitive emissions.

TheMrbunGee - 10-12-2016 at 23:40

You can also react sulfur with aluminum powder, then react aluminum sulfide with water to have H2S!

[Edited on 11-12-2016 by TheMrbunGee]

AJKOER - 11-12-2016 at 05:13

Comments on Al2S3 preparation from Wikipedia (https://en.m.wikipedia.org/wiki/Aluminium_sulfide ), to quote:

"Aluminium sulfide is readily prepared by ignition of the elements[6]

2 Al + 3 S → Al2S3

This reaction is extremely exothermic and it is not necessary or desirable to heat the whole mass of the sulfur-aluminium mixture; (except possibly for very small amounts of reactants). The product will be created in a fused form; it reaches a temperature greater than 1100 °C and may melt its way through steel. "

Note, I suspect more accurately, the burning of sulfur and Al likely forms polysulfides also and with water, polysulfides of hydrogen (for example, H2S2).

A less 'hot' approach is electrochemical based on the so called Aluminum Sulfur battery (see, for example, "Aluminum and sulfur electrochemical batteries and cells", US patent 5,413,881, link: http://www.google.com/patents/US5413881 and a more academic reference, https://www.google.com/url?sa=t&source=web&rct=j&... ). The cell reaction is given generally as:

2 Al + 3S + 3OH- + 3H2O → 2Al(OH)3 + 3HS- ; Ecell =1.8 V

where I would employ an excess of Aluminum. Now, if one adds an acid source to the product, expect H2S. However, my last reference mentions a polysulfides presence as well, so again not a pure product.

[Edited on 11-12-2016 by AJKOER]

unionised - 11-12-2016 at 05:38

It's a matter of definition of "acid" but adding water to Al2S3 will make H2S.

If you react an excess of aluminium with sulphur you won't get polysulphides.

The lightest hydrogen polysulphide boils at about 70C and is thus likely to be left behind in the reaction mixture.

Even when you try to make the hydrogen polysulphides the yield is poor, so I doubt you will get much of it by accident.

The big problem with using Al as the reducing agent is that the Al/S reaction is very violent.
Iron works fine; why make things difficult?

Derek McOlund - 11-12-2016 at 09:06

Well I'm working on a projekt to convert MnSO4 into H2SO4 and MnS, that's possible to do with H2S: H2S + MnSO4 --> MnS + H2SO4.
In this project I'm trying to not use as easy available chemicals as possibly, and HCl isn't very easy to buy.

Metacelsus - 11-12-2016 at 09:26

Quote: Originally posted by TheMrbunGee

You can also react sulfur with aluminum powder, then react aluminum sulfide with water to have H2S!

I've done this; it works quite well. Keep in mind that the reaction is highly exothermic, so don't run it in anything you care about.

nezza - 12-12-2016 at 01:17

You will not be able to make H2SO4 from MnSO4 and H2S in an aqueous environment. MnS has a highish solubility product and is soluble in dilute H2SO4 so the equilibrium H2S+MnSO4 <> MnS +H2SO4 lies well to the left. Adding MnS to aqueous H2SO4 gives H2S, rather that the reaction working the other way.

ave369 - 12-12-2016 at 01:53

One could try this with CuSO4. CuS has very, very low solubility, if I remember correctly.

Amos - 12-12-2016 at 08:02

Quote: Originally posted by Derek McOlund

Well I'm working on a projekt to convert MnSO4 into H2SO4 and MnS, that's possible to do with H2S: H2S + MnSO4 --> MnS + H2SO4.
In this project I'm trying to not use as easy available chemicals as possibly, and HCl isn't very easy to buy.

This isn't going to work at all, unfortunately. Just as we've been describing the reactions of various metal sulfides reacting with even weak acids like water below, manganese sulfide produced would only immediately react with sulfuric acid formed as a co-product and regenerate hydrogen sulfide. This is the same reason you couldn't add carbon dioxide to a solution of manganese sulfate to precipitate the carbonate; a weaker acid like carbonic acid or hydrogen sulfide will not displace a stronger acid from a salt, at least as a general rule.

[Edited on 12-12-2016 by Amos]

MnS Preparation

WGTR - 12-12-2016 at 12:53