Ferrous sulfate is a kind of low molecular ferrous salt, the ferrous ion easily in the air is oxidized to ferric iron, so the water solution from light green to yellow, and the conversion time soon, often make people mistakenly think that the original color is yellow. So in the purchase of ferrous sulfate, and how to detect the quality of ferrous sulfate?
According to different process mainly we usually use ferrous sulfate into two kinds: the first one is the feed grade ferrous sulfate commonly known as ferrous sulfate seven water, the product is a byproduct of titanium dioxide plant using ferrous sulfate as raw material through refined processing; the second is industrial grade ferrous sulfate or ferrous sulfate, usually on the net agent and disinfectant, way to identify genuine ferrous sulfate the sensory examination and laboratory examination: the first sensory test, seven water ferrous sulfate and ferrous sulfate is generally pale green or monoclinic crystalline particles, no other pungent odor, soluble in water solution was light green, second laboratory testing should be said to be the most simple, the most effective method, the product is soluble in water, shake, anhydrous ferrous sulfate is white powder, water of crystallization is light green crystal crystal, commonly known as "copperas", used for chromatographic analysis Drop analysis reagent, determination of platinum, selenium, and no movement and no movement, reducing agent, manufacturing ferrite.
There are various methods to test whether the deterioration of ferrous sulfate. People commonly used detection method of sodium hydroxide solution such as ferrous sulfate and sodium hydroxide solution. The reaction after the formation of reddish brown precipitate, namely ferrous hydroxide, but is very unstable, and very easily oxidized to reddish brown precipitate. The phenomenon is not obvious, is not easy to distinguish. So no movement is sulfur our best choice. We will put the ferrous sulfate beaker, adding sulfur solution if no movement, the solution turns red, indicating deterioration, two valent iron by oxygen into trivalent iron. No movement, this reagent encounter Fe3+ becomes blood red, difficult to form a decomposition of the conjugates. If the modification is ferrous sulfate that is oxidized to ferric sulfate, this method is very accurate.