# Preparation of ferric hydroxide sol

I have read that before the preparation of ferric hydroxide sol, the beaker must be cleaned by the steaming out process, while it is not necessary for starch sol. Why is that?

• It might be because starch sol is quite stable to impurities, whereas ferric hydroxide sol isn't. I am quite sure that is also mentioned in your book. – ShankRam Feb 10 '16 at 9:18