Sciencemadness Discussion Board - Sodium sulphide

Sodium sulphide

nezza - 10-3-2012 at 12:18

Is there a simple way to make small quantities of sodium sulphide, not via hydrogen sulphide. I can buy kilogram quantities on line but I only need a few grams.

entropy51 - 10-3-2012 at 13:02

Quote: Originally posted by nezza

Is there a simple way to make small quantities of sodium sulphide, not via hydrogen sulphide. I can buy kilogram quantities on line but I only need a few grams.

There have been threads on this in the past. The methods that do not use hydrogen sulfide are not simple, they are worse than using H2S for the most part.

You can buy it online from photo suppliers. $5 for 100 grams.

AJKOER - 10-3-2012 at 17:54

Here is an interesting path (most likely untried). First, an interesting reaction, heat S and Al (avoid moisture):

2 Al + 3 S --> Al2S3

Depending on how fine the Al, this could be very exothermic (think flash powder).

Add an excess of NaOH and heat again:

6 NaOH + Al2S3 --> 3 Na2S + 2 Al(OH)3

More interesting do it all at once by constructing consecutive layers of Aluminum and Sulfur mix, pure sulfur and then NaOH. Apply heat or ignite.

The reason for the pure S layer is as buffer between Al and the NaOH, which is hygroscopic.

[Edited on 11-3-2012 by AJKOER]

woelen - 11-3-2012 at 23:18

Do you really believe this will give a clean product? NaOH and S also react with each other, without the Al. This combination gives a very complicated mix of sulfide, thiosulfate and polysulfide (the potassium compound made in this way is called liver of sulphur, which is very far away from pure sulfide).

Making pure Al2S3 seems achievable to me, but it will not be easy. Expect a lot of unreacted aluminium and sulphur and also expect polysulfides in the mix. This kind of solid-solid reactions hardly ever give pure products and quantitatively well defined reactions. The main reaction is formation of Al2S3, but there are side reactions.

AJKOER - 12-3-2012 at 13:45

Yes, I agree, certainly not a pure synthesis, but an OK excuse to react Al and S and amazingly easier (fun) way than the standard preparation for the anhydrous salt, albeit with an Al2O3 impurity. For example, per Wikipedia:

"Production
Industrially Na2S is produced by reduction of Na2SO4 with carbon, in the form of coal:[3]

Na2SO4 + 4 C → Na2S + 4 CO

In the laboratory, the anhydrous salt can be prepared by reduction of sulfur with sodium in anhydrous ammonia. Alternatively, sulfur can be reduced by sodium in dry THF with a catalytic amount of naphthalene:[4]

2 Na + S → Na2S"

To my prior Aluminum sulfide suggested route, here is a modification: Add strong NH4OH to any of the Al2S3 that may have formed along with any possible un-reacted Sulfur and Aluminum. Filter out (unfortunately, the bad smell of H2S from the Ammonium Sulfide has not been avoided). Expected reaction:

Al2S3 + 2 NH3 + 4 H2O --> (NH4)2S + 2 Al(OH)3

where water is consumed and one can use the flocculation property of Aluminum hydroxide to help clean the solution from particles.

Now add the NaOH (in excess) and mildly heat or, possibly better, add some alcohol in which Na2S is only slightly soluble, to move the reaction to the right. Then, cool to isolate Na2S.xH20, which is the commercially available hydrate. Reaction:

(NH4)2S + 2 NaOH --> Na2S + 2 NH3 (g) + H2O

A source notes the following unwanted reaction:

Na2S + 2 H2O <----> 2 NaOH + H2S

The result, if successful, is hopefully a somewhat cleaner Na2S product in hydrated form.

[Edited on 13-3-2012 by AJKOER]

nezza - 15-3-2012 at 02:30

Thanks for the answers. I have found a supplier I can get 100g off so that will do. One more question - How stable is it in aqueous solution ?.

Endimion17 - 15-3-2012 at 04:56

The sulphide anion hydrolizes and forms hydrosulfuric acid which is very weak, so most of the H<sub>2</sub>S molecules exist as hydrogen sulphide which slowly evaporates from the solution. Generally speaking, it takes over 15 minutes for the stench to fully develop after the solid has been dissolved in water.

AJKOER - 16-3-2012 at 07:37

Quote: Originally posted by Endimion17

The sulphide anion hydrolizes and forms hydrosulfuric acid which is very weak, so most of the H<sub>2</sub>S molecules exist as hydrogen sulphide which slowly evaporates from the solution. Generally speaking, it takes over 15 minutes for the stench to fully develop after the solid has been dissolved in water.

Per my cited equation:

Na2S + 2 H2O <----> 2 NaOH + H2S

In an open vessel, the formation of H2S gas means that the equilibrium is moving to the right. But, in a closed container with a little added NaOH, the smell should be less noticeable upon opening assuming the vessel is not heated. Also, upon cooling, the formation of the hydrate moving the reaction to the left.

[Edited on 16-3-2012 by AJKOER]

BauArf56 - 23-4-2021 at 04:40

i know thread is old, but heating sulfur with an excess of sodium carbonate gives sodium sulfide and carbon dioxide (if an excess of sulfur, it will react to form polysulfides).

Bedlasky - 23-4-2021 at 06:21

There will be thiosulfate as impurity.

unionised - 23-4-2021 at 06:50

Heating sulphur with sodium carbonate will give a mixture of sulphide and thiosulphate.

Which is probably still better than heating a mixture of aluminium, sulphur and sodium hydroxide which will give you a shower of molten alkali (with some sulphide, for added toxicity)

RU_KLO - 2-4-2023 at 10:09

I need some sulphide for qualitative chemistry (sulphide precipitation). Never used this procedure.

I do not own a fumehood, and know that H2S is toxic. This is why I try to avoid it.
I read that Na2S could be used instead. After reading this post and others from wiki (SM), tried this process:

An arbitrary ammount of Sulfur (powered) and Sodium carbonate was heated in a test tube (-TT) (this was done outside). The TT was heated with an alcohol burner till the sulfur melted. It became a black liquid (some sulfur deposited in the neck of the TT)
After 5 minutes or so, the TT was removed from heat. Cooled (it solidifies in a red-orange rock) and breaked. The red-orange rock was crushed.

I read that this is a mixture of sulphides, polysulphides, thiosulfates, and probably sulfur and sodium carbonate.

Cold (1-2° H2O was poured. the idea was that Na2S is less soluble in cold H2O than thiosulfate.

but everything was dissolved. Giving a orange solution.

A few drops of this solution was dropped in a solution of Lead nitrate. Black/Brown precipitate immediately appeared. So probably some sulphide is in there.

Questions:
1) Is there a way to purify this solution?
2) Could be used as it is for qualitative chemistry? (or the thio - poly sulfides/sulfates will interfere?)
3) Currently is stored in a pyrex capped bottle (80 ml), and as I do not own a fumehood, how dangerous is to work with this solution inside my house?
The idea is to use 3-5 drops each time.
4) Read that Na2S hydrolyses, this means that as time pases, the solution will be useless?

Thanks,

[Edited on 2-4-2023 by RU_KLO]

woelen - 4-4-2023 at 00:09

1) I see no easy way to do that. Soooo many impurities!
2) I would not use it for any analytical purposes. As I said, soooo many impurities!
3) Yes, you can safely use this inside the house. Things may be somewhat smelly, but using a few drops of solution will not lead to dangerous amounts of H2S in the air. Even on addition of acid to these few drops you will only get a bad smell, but no dangerous concentration of H2S.
4) It hydrolyses, but that is an almost immediate reaction. As soon as you add Na2S to water, the sulfide is almost completely hydrolysed to SH(-) ions: S(2-) + H2O --> SH(-) + OH(-). This reaction is nearly instantaneous, and nearly 100%. The sulfide, however, still remains sulfide in this reaction. If you have a sulfide solution and no air can get in, then the sulfide will remain good (as SH(-) ions). If air is allowed to reach the solution, then it quickly degrades. Sulfide is oxidized to sulfur (and OH(-) is formed in the process as well), and this reacts with more sulfide to yellow polysulfides. If a lot of air is allowed to come in contact with the solution, it will become turbid and impure sulfur will precipitate. You also will get all kinds of oxo-compounds of sulfur in solution, it will become a very complicated (and smelly) mix.

blogfast25 - 4-4-2023 at 05:26

Consider making FeS instead. Treated with strong acid this then generates the desired H₂S.

Simply combine Fe and S and heat to get the party started:

Fe(s) + S(l) --> FeS(s) (+ much heat)

The FeS obtained is relatively pure.

[Edited on 4-4-2023 by blogfast25]

Cathoderay - 4-4-2023 at 10:25

Here is a link to Doug's Lab making iron sulfide.
https://www.youtube.com/watch?v=CLBdVM9_FWg

For the small amount you may need there could be another way.
I haven't tried it but I do think that if you mix paraffin wax and sulfur and heat it in a test tube it will produce H2S gas.
You can fit a one hole stopper on the test tube with a bent glass tube that is inserted into the solution you are adding the H2S to.
Some paraffin wax might evaporate and condense in cooler areas and possibly SO2 might be generated but those should not interfere with the process.

Admagistr - 4-4-2023 at 10:29

For the small amount you may need there could be another way.
I haven't tried it but I do think that if you mix paraffin wax and sulfur and heat it in a test tube it will produce H2S gas.
You can fit a one hole stopper on the test tube with a bent glass tube that is inserted into the solution you are adding the H2S to.
Some paraffin wax might evaporate and condense in cooler areas and possibly SO2 might be generated but those should not interfere with the process.
[/rquote]

The reaction of paraffin with sulphur to produce H2S is a known reaction and it works, often with the addition of Al2O3 as a catalyst, the reaction has the advantage that the development of H2S stops immediately after stopping the heating.

[Edited on 4-4-2023 by Admagistr]

blogfast25 - 4-4-2023 at 10:32

Quote: Originally posted by Cathoderay

I haven't tried it but I do think that if you mix paraffin wax and sulfur and heat it in a test tube it will produce H2S gas.

Well, live and learn: never previously heard of that one...

[Edited on 4-4-2023 by blogfast25]

Admagistr - 4-4-2023 at 10:42

Quote: Originally posted by blogfast25

Quote: Originally posted by Cathoderay

I haven't tried it but I do think that if you mix paraffin wax and sulfur and heat it in a test tube it will produce H2S gas.

Well, live and learn: never previously heard of that one...

[Edited on 4-4-2023 by blogfast25]

The reaction is often reported in the literature and works,but I can't remember the citations at the moment.I read it in about five books on preparative inorganics,it's many years ago...

B(a)P - 4-4-2023 at 12:32

Quote: Originally posted by Admagistr

Quote: Originally posted by blogfast25

Quote: Originally posted by Cathoderay

I haven't tried it but I do think that if you mix paraffin wax and sulfur and heat it in a test tube it will produce H2S gas.

Well, live and learn: never previously heard of that one...

[Edited on 4-4-2023 by blogfast25]

The reaction is often reported in the literature and works,but I can't remember the citations at the moment.I read it in about five books on preparative inorganics,it's many years ago...

Here is a good demo by Tdep https://www.youtube.com/watch?v=1hfC_ggJEhs

blogfast25 - 4-4-2023 at 12:43

Boy, was that longwinded or was it longwinded?

Not to mention a superfluousness of glass porn...

You could also use scrap PE bags as a hydrocarbon, I guess.

[Edited on 4-4-2023 by blogfast25]

Cathoderay - 4-4-2023 at 18:53

Quote: Originally posted by B(a)P

Quote: Originally posted by Admagistr

Quote: Originally posted by blogfast25

Quote: Originally posted by Cathoderay

I haven't tried it but I do think that if you mix paraffin wax and sulfur and heat it in a test tube it will produce H2S gas.

Well, live and learn: never previously heard of that one...

[Edited on 4-4-2023 by blogfast25]

The reaction is often reported in the literature and works,but I can't remember the citations at the moment.I read it in about five books on preparative inorganics,it's many years ago...

Here is a good demo by Tdep https://www.youtube.com/watch?v=1hfC_ggJEhs

I think he got a little too ambitious and made too much and got it too hot. I had seen a analysis video somewhere that showed a dark substance in a test tube heated with a Bunsen burner, the test tube having a stopper and bent glass tubing. The substance was not identified. I think the apparatus was kept as is, you don't reuse the test tube. It is meant for qualitative analysis of solutions in test tubes not for synthesis.

blogfast25 - 4-4-2023 at 22:59

Quote: Originally posted by Cathoderay

I'll defo try this one day but much simplified. Considering the chemical inertia of paraffins (olefins, see etymology!) I'm surprised this reaction proceeds at all!

The FeS route has the benefit of leaving you with a bit of a portable H₂S source, to be deployed when needed.

teodor - 5-4-2023 at 01:52

Quote: Originally posted by RU_KLO

I need some sulphide for qualitative chemistry (sulphide precipitation). Never used this procedure.

I do not own a fumehood, and know that H2S is toxic. This is why I try to avoid it.
I read that Na2S could be used instead.

Indeed, there are alternatives for H2S and depending on what you try to analyze different reagents could be used: thiosulfate, thioacetate, thioacetamide, impure Na2S or even S- free reagents like solvents or chelating agents.

So, main question is: which ions you try to separate and whether you need qualitative or quantitative results.

Making home chemistry last few years I learned that there is an alternative to almost every reaction but there is no alternative to a fume hood. Start to make it step by step, starting from the suction part.

woelen - 5-4-2023 at 02:38

I tried the reaction of paraffins (from candles) with sulfur. It indeed works, and you can make a fairly constant stream of H2S. The biggest disadvantage is that there are impurities in the H2S, which are annoying when you want it to make a solution of sulfide (e.g. by bubbling it through water). I obtained a yellow liquid, because vapor of sulfur goes with the H2S, and although most of it will condense, some sulfur makes it into the H2S, going into the solution. The reaction also produces some annoying hydrocarbons, which may make it into the solution.

So, I prefer the FeS-route. FeS, made at home, also is quite impure in my experience, but it can be used for making nice pure alkaline solutions of sulfide. If you mix the impure FeS with acid, then you get H2S and H2 (from unreacted iron), but that H2 does not contaminate your target solution. The FeS also may contain unreacted sulfur, but at the low temperatures in the aqueous acid, this does not escape and move with the H2S. You just don't get a clear solution in the flask to which the FeS is added, but the gas mix is clean. The only problem with production of H2S from FeS and dilute acid, is that droplets of solution can be taken with the H2S, but that problem can be reduced a lot, by using a long tube, and by using a tube, filled with very loosely packed wadding or glass wool. Any droplets you have remain behind.

The H2S can be bubbled through an aqueous solution of NaOH, which leads to an alkaline solution of a mix of NaHS and NaOH. But a solution of Na2S also is a mix of these two.

teodor - 5-4-2023 at 03:25

Quote: Originally posted by woelen

The H2S can be bubbled through an aqueous solution of NaOH, which leads to an alkaline solution of a mix of NaHS and NaOH. But a solution of Na2S also is a mix of these two.

The classical method of preparing ammonium sulfide as an analytical reagent includes saturating ammonium solution with H2S and adding ammonium solution equal to initial volume after that. Based on this I suspect when H2S is absorbed the final result could be mostly HS-.

Update: the complexity of using Na2S of (NH4)2S as an analitical reagents is that it is possible only in alkaline to netral condition, but H2S systematic analysis is started with acidic solutions.

[Edited on 5-4-2023 by teodor]

RU_KLO - 5-4-2023 at 05:05

If I would like to build an aspirator/scrubber, for H2S.

as simple as a Pc 10 cms fan + funnel + hose + washing bottle.

Like I said it will work with very small quantities, but If the smell could also be reduced, the better.

What should the washing bottle contain? (I used H2O2 to neutralize some experiments with my impure Na2S solution)

If H2O2 is the best method, which concentration?

(please note that other gases from the reaction could be sucked into the washing bottle that could react with H2O2 - I do not know this, is a thinking.)

teodor - 6-4-2023 at 00:48

You still need a general ventilation for the case something goes wrong.
I would recommend FEP / glass as a piping. Other matherials could be easily penetrated by H2S.
Use a normal vacuum greese for all joints. Fix everything, the good fixing is essential for gas experiments. Invest in steel rods frame and a good set of clamps before investing in ventilation.
Don't relay on scrubber much. You can use NaOH + NaOCl as a first stage and optionally a solution of metal salt CuSO4 , FeSO4 as the second. Fe(III) salts are even better - they combine oxidation effect with precipitation. But in any case attach a long glass of FEP pipe with one side being outside your lab to dispose the unabsorbed excess.
To disassemble the apparatus use a water aspirator (on low suction) to suck the rest of H2S out of your apparatus through scrabbers which will mix and dispose any unabsorbed gas with water.

[Edited on 6-4-2023 by teodor]

As a method of H2S generation without FeS one can try boiling NaOH with S. It should form polysulfide solution first (the red one) but then you start to distill water and it should come with H2S. It is not so convenient when you need H2S for analytical purposes but for some experiments with H2S it could be ok.

[Edited on 6-4-2023 by teodor]

bluamine - 19-4-2023 at 14:31

You can try boil sodium hydroxide solution with sulfur until this latter completely dissolves, and then mix it with an aqueous solutions of aluminium chloride, that will release hydrogen sulphide so you must bubble it through an aqueous solution of sodium hydroxide