Sciencemadness Discussion Board - How toxic is H2S?

How toxic is H2S?

vmelkon - 27-1-2021 at 20:35

How toxic is H2S?
I made some Al2S3 by direct reaction of the elements.
I took a couple of whiffs and I could smell the rotten eggs smell.

It’s an interesting compound. I don’t think I ever smelled the rotten egg smell when I made CuS and FeS.

~~~~vmelkon

DraconicAcid - 27-1-2021 at 21:02

The iron and copper sulphides are very insoluble, and won't hydrolyze with moisture. Aluminum sulphide will.

Velzee - 27-1-2021 at 21:06

They say it's similar to HCN, but the numbers tell otherwise: LC50 H2S 800 ppm (human, 5 min), LC50 HCN 200 ppm (mammal, 5 min).

Al2S3 reacts with water to form H2S: Al2S3 + 6H2O --> 2Al(OH)3 + 3H2S

B(a)P - 27-1-2021 at 21:10

It is quite toxic, with symptoms experienced at concentrations as low as 5 ppm.
Exposure at concentrations greater than 100 ppm will potentially lead to eye and respiratory tract damage.
Exposure at concentrations greater than 1000 ppm will likely result in immediate unconsciousness followed shortly by death due to paralysis of the respiratory centre in the brain.
If you experienced a headache, sore eyes or irritated airways you were likely exposed to 5 to 20 ppm.
You can detect the odour at concentrations lower than 1 ppm, but will quickly become desensitised to the odour.
For a once off exposure, if you had no to mild symptoms, then you have little to worry about.

FrenchChemist - 27-1-2021 at 21:44

Exactly, the worst thing about H2S is that at a certain concentration it paralyzes the sense of smell, therefore the path to further inhaling completely unconsciously and taking a lethal dose is very short.

j_sum1 - 27-1-2021 at 22:18

I am maybe a bit overfamiliar with H2S. Growing up I frequented geothermal regions where you could smell on a daily basis the H2S arising from the ground and stormwater drains: generally accompanied by a lot of water vapour as well. Ambient air in Rotorua gets as high as 0.03ppm and I am very familiar with that level.

So, now, if I smell H2S then I associate it with those memories. I am confident that concentrations above the odour threshhold are not going to do me any harm.
However, if it becomes too whiffy, enough to be unpleasant, then I know I am above the levels I want. And I know that at higher levels I am likely to be desensitised, although, I have never experienced levels that high.

In practice, I don't shy away from H2S but I do take precautions: scrubbing and fume-hood if possible. If a little gas escapes or I am doing something at small test-tube scale and I smell it, I am not at all worried.
If I have to do anything that is likely to produce significant quantities (and I have some future projects that will) then I intend to set up a good scrubbing system, work in a fume hood and also set up some test strips. I don't intend to rely on smell for safety. Nor am I going to freak out if I do happen to smell a small amount. It is also useful to do a quick calculation to find out how much you are making and what the maximum concentration in your workplace might be.

HCN I really don't have experience with. I do not know its smell and I understand that some people cannot smell it anyway. Not that I have had any need up to this point, but when I do end up working with HCN, I am likely to be a lot more nervous than I would be with H2S.

I feel like I have waffled. I guess I am saying that experience, confidence, and knowledge, as well as quantity control, are just as valuable in mitigating hazards as any amount of PPE or other safety measures. Where there exist suitable sensory indicators of danger then it is useful to know them and work with them. But without appropriate knowledge, smell is is a really unreliable indicator.

Fluorite - 27-1-2021 at 22:45

I've never smelled rotten eggs when working with H2S! The smell is disgusting but like lemons IMO :3

FrenchChemist - 28-1-2021 at 00:31

Quote: Originally posted by Fluorite

I've never smelled rotten eggs when working with H2S! The smell is disgusting but like lemons IMO :3

I think a lot depends on the method of obtaining it.

Most are synthesized from sodium sulfide or Iron (II) sulfide.

I had very pure sodium sulfide at my disposal as well as very yellow (technical) - in my opinion, in a large number of people the "admixture" of impurities has a significant impact on the smell.

vmelkon - 28-1-2021 at 07:34

Well, the good news is, that I am fine.
The next step is to convert that into hydrosulfuric acid. I will be doing test tube quantity, actually, 25% of a test tube. Maybe I have 3 g of Al2S3.

xxxhibition - 29-1-2021 at 10:00

Quote: Originally posted by FrenchChemist

Quote: Originally posted by Fluorite

I've never smelled rotten eggs when working with H2S! The smell is disgusting but like lemons IMO :3

from Childhood to now in Test Tube Sizes a lot of Fun here gasing my Workshop Neighbours. :cool:

zed - 8-2-2021 at 23:51

H2S and HCN? I fear them equally. And, that's plenty.

Lots of H2S around. Gives you something to think about.