Korenje

Hy!I have a question about ionic reactions (precipitation, color change). I need to prepare a short experiment. It must be interesting without, dangerous chemicals and without warming. It will be performed by 14-year-old students. Anyone have any idea? Is the experiment on this connection a part of ion reactions? https://melscience.com/en/articles/egyptian-night-experiment-190418/?utm_source=FBpost_en&utm_medium=EgyptianNight190418_article_enThank you for any information.