The chemistry 🧪🧪⚗️ kit I wanted to make based on etching

Maybe people could make kits with a solid metal like iron or copper and acid and how it will will take 60.12 seconds to dissolve based on provable chemical equations to see full change in color to prove stochiometery with a write up that way you will get whole numbers from nature... Doing reaction and precipitaion is hard.. as you have to buy centrifuge and weiging scale maybe..