# What are differences between "Mohr's salt", and "green vitriol"?

Well, $\text{green vitriol}$ is $F e {\left(S O\right)}_{4}$, an iron(II) salt.........
And $\text{Mohr's salt}$ is ${\left(N {H}_{4}\right)}_{2} \left[F e {\left(S {O}_{4}\right)}_{2}\right] \cdot 6 {H}_{2} O$.
In solution, however, for both species, we LIKELY have ${\left[F e {\left(O {H}_{2}\right)}_{6}\right]}^{2 +}$ as the dominant iron species in solution. The sulfate and ammonium counterions are along for the ride. There is possibly some literature on this, which is likely informed by $\text{UV-vis spectrometry}$.