Why does 68-70% sulfuric acid appear green?
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This post was last edited by liu530014416 on 2022-6-15 08:31. Dear teachers, the process uses 68–70% sulfuric acid at 100 degrees Celsius; nitric acid at 65% concentration reacts with benzene to undergo nitration, with sulfuric acid acting as a catalyst. This acid is recycled within the enamel system, and over time its color turns green. What is the reason for this? 70% is considered concentrated sulfuric acid, right? Can ferrous ions exist in it? Moreover, the laboratory tested for iron ions and no iron ions were found.
Metal ions or organic substances introduced during production
That certainly isn’t the natural color of sulfuric acid; we need to check whether there are ferrous ions or copper ions present – those are the most common ones
This post was last edited by yyong110 on 2022-6-14 at 12:20. Although 68-70% concentration still counts as concentrated sulfuric acid, its acidic corrosion rate on carbon steel materials is already quite fast. Basically, acidic corrosion accounts for a larger proportion than oxidative corrosion. Since the ferrous ions come from the container or pipes, there is an excess of iron in the entire system; therefore, ferrous ions will definitely be in the majority. Trivalent iron and iron together produce divalent iron. Generally, carbon steel containers are not recommended for sulfuric acid at this concentration.
What causes the acid at 105% to turn milky white?
The color of ferrous ions; 70% sulfuric acid is highly corrosive