The color of ferrous sulfate solution is light green because ferrous ions in ferrous sulfate solution appear light green in water.
It should be noted that ferrous sulfate solution is an unstable solution and is basically freshly prepared.
If the ferrous sulfate solution is left for a long time, the ferrous ions in it will undergo an oxidation reaction with the oxygen ions in the water, and the ferrous ions will be oxidized to trivalent iron. This will turn the green ferrous ions into yellow trivalent iron ions. So many people mistakenly believe that ferrous sulfate solution is yellow, which is incorrect.
The correct preparation method for ferrous sulfate solution
Prepare dilute sulfuric acid to prevent the hydrolysis of ferrous sulfate into ferrous hydroxide;
Add an appropriate amount of ferrous sulfate solid to dilute sulfuric acid;
After the solid ferrous sulfate dissolves, add a small amount of reduced iron powder to prevent ferrous ions from being dissolved and oxidized.
Reminder: Ferrous sulfate solution should be used and prepared immediately. After preparation, it should be used up in a short period of time and should not be stored for a long time.
What color is solid ferrous sulfate
Ferrous sulfate: a white powder that is soluble in aqueous solution and turns light green. Its crystals are commonly known as "green alum".
Hydrated ferrous sulfate is a blue-green monoclinic crystal or particle, odorless. Weathering in dry air and oxidizing to brown alkaline iron sulfate on the surface in humid air. It becomes a tetrahydrate at 56.6 ℃ and a monohydrate at 65 ℃. Soluble in water, almost insoluble in ethanol. Its aqueous solution oxidizes slowly in air when cold, and oxidizes quickly when hot. Adding alkali or exposure to light can accelerate its oxidation. Relative density () 1. It is stimulating. Anhydrous ferrous sulfate is a white powder, with light green crystals containing crystalline water, commonly known as "green alum". When dissolved in aqueous solution, it becomes light green. Ferrous sulfate can be used as a chromatographic reagent and for the determination of platinum, selenium, nitrite, and nitrate in drop analysis. Ferrous sulfate can also be used as a reducing agent, manufacturing ferrite, water purification, polymerization catalyst, photographic plate making, etc.