Is dissolution of H2S in water exothermic?

While doing certain laboratory tests for qualitative identification of cations, I found that on passing $\ce{H2S}$ in the solution, the temperature of the solution increased considerably. When the temperature decreased due to addition of $\ce{NH4Cl}$, the solution again attained room temperature in passing $\ce{H2S}$.


This rouses the question: is the dissolution of $\ce{H2S}$ in water exothermic? Or does it react with other components of solution to make an exothermic reaction?


The [Wikipedia article](https://en.m.wikipedia.org/wiki/Hydrogen_sulfide) stated only this:



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> Hydrogen sulphide is slightly soluble in water and acts as a weak acid (pKa = 6.9 in 0.01–0.1 mol/litre solutions at 18 °C), giving the hydrosulfide ion $\ce{HS^−}$. Hydrogen sulphide and its solutions are colourless.
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The full experiment can be found [here](https://chemistry.stackexchange.com/questions/84693/cooling-down-and-heating-of-solution-unexpectedly-during-cation-identification-t).




[Koschel et al. (2013, p. 14486)](https://pubs.acs.org/doi/pdf/10.1021/ie401947h "Koschel et al. (2013)") report that 



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> dissolution of gaseous hydrogen sulfide in aqueous phase is *exothermic* at conditions where $\ce{H\_2S}$ is gaseous, i.e., at a temperature of 323 K and pressure 2 MPa, the saturation pressure $p\_\text{sat}(\mathrm{H\_2S})$ being 3.5 MPa. The dissolution process is *endothermic* at the medium and highest temperature where hydrogen sulfide is liquid and supercritical, respectively, the critical parameters of $\ce{H2S}$ being $T\_c = 373.4$ and $p\_c = 8.94$ MPa.
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