[mistryous]

How do they make the sniffing sticks that smell of H2S for over a month or so?  Any ideas for what's inside the pens?

[Borek]

You mean the ones used for smelling tests?

[marquis]

Yeah, not sure the exact test being described.  The stick's  carried in the hospital used to revive someone generated Ammonia, not h2s ( they were most often used when showing a relative a body in the morgue, unfortunately). Are these the ones being asked about?

[mistryous]

No, not the ammonia test, but H2S smelling test sticks. They use smelling sticks for training so you know how different gases smell. Also for all kinds of aromas, but H2S is not easy to get into a stick. It is very special because usually the smell is quickly gone. So how can you make it last in small concentrations? How can you conserve this odor for some time is the question.

[Hunter2]

Get ironsulfide FeS and add some acid (sulfuric, hydrochloric, acetic acid, etc.)

[mistryous]

But then the odor won't last too long which is exactly the problem. How would you make it last longer over time so that you could use it for a smelling sample impression again and again, at least for a week or so?

[Borek]

Not that I have an exact proposition, but I would look for any sulfide mixed with some substance that slowly hydrolyzes producing an acid in the presence of water in air - such a mixture should produce H₂S very slowly and for a long time (and you really need hydrogen sulfide in a very minute amounts, smell can detect some insanely low concentrations).

Or something similar to thioacetamide, which easily hydrolyzes in hot water, producing the gas. Just something that doesn't need elevated temperature. Or put it in a device similar to vapes, with a small battery run heater.

[mistryous]

Wow, 2 possibilities that are completely new to me!

1.
So are you saying that there are some substances that keep changing into acids as they only have contact with the (water in the) air? And the air should have a certain temperature then? What would be some examples for such substances and what temperature would be necessary?

2. Thioacetamide just in water would work? At room temperature? Or above 20°C?

[Borek]

So are you saying that there are some substances that keep changing into acids as they only have contact with the (water in the) air? And the air should have a certain temperature then? What would be some examples for such substances and what temperature would be necessary?

For example most acid anhydrides work this way. Some are more sensitive to water and will react very fast, some will react slower, no simple answer tou your questions.

And acid anhydrides are definitely not the only substances that behave this way.

Thioacetamide just in water would work? At room temperature? Or above 20°C?

In classical inorganic analysis thioacetamide is used in hot water bath to precipitate sulfides. It does react in low temperatures as well, but much slower (basic kinetics). It is highly possible other thioamides will decompose much easier at room temperature (but no, I can't give examples, this is just prediction based on how the chemistry works in general).

[mistryous]

This is really informative to me. Please more input like this - also if anyone else would like to join in go ahead.

[Aldebaran]

Wikipedia has information about olfactory fatigue which may be of interest to you.

[marquis]

Definite issue of concern with H2S.  We used H2S for heavy metals testing per the USP.  Always did it under a hood. But still...The issue of not being able to smell it if it got to strong always bothered me (and hopefully others)..

[Hunter2]

H2S is like HCN in power of poisson.
Danger is in high concentration  you cannot smell it anymore cause deadly accidents.

[Borek]

Yes, H₂S is highly toxic and dangerous. My bet is these test sticks are made in such a way they don't contain enough sulfur to be dangerous (which is actually another reason why they can be difficult to replicate).