You can get methane, ammonia, and hydrogen sulfide in absence of air, also other oxidized forms of the same and similar molecules in presence of air. The first is called septic, and the second is called fresh, but with a technical liberty applied to the word fresh.

Usually for the domestic syphon the oxidized form are smelled. The remedy is to pour a small quantity of water into the syphon to prevent gas escaping.

Thank you Jerry Decker

I understand that you mean: CH4, NH3 and H2S in absence of O2 and

CO2, H2O. NO2, SO2....etc in presence of O2 ..but is it possible that  NH3 (basic character) could exist simultaneously with H2S (acidic character) in the same solution ??

Regards

Thank you very much Luis.

A solution can contain NH3 and H2S, but they neutralize each other forming NH4SH.

Hello Marko

I know that if they exist together in the same solution a neutralizing reaction occurs for this reason i asked my question ....

I hope that this will answer your question.

Thank you very much for this useful file.

Regards.