The visual evidence for a precipitation reaction is always the same: there is some change in the clarity of the mixture. Sometimes the change is very dramatic and the entire solution becomes opaque. After some time the new solid material may settle completely, leaving a clear solution above once again.

But not all precipitates are as heavy or obvious. Sometimes a vague sort of cloudiness is all you will see. Contrasting color backgrounds are often very helpful in discerning such precipitates, as is stirring the solution slowly.

Precipitates come in many colors, as the demonstration illustrates. Most often the highly colored solids contain one of the transition metals.