Disposal of agar containing silver nitrate: How should I dispose of an agar plate containing silver nitrate? It was used to create crystals with a piece of zinc.

Disposal of agar containing silver nitrate: How should I dispose of an agar plate containing silver nitrate? It was used to create crystals with a piece of zinc.
Labelling silver nitrate: I am labeling some Silver nitrate solution with Gold FFX and saw that it doesn't come up with any Pictograms but says it is harmful to aquatic life.
Bonding and conductivity: Our Year 11s had an electrical conductivity practical demonstrated to them, and the molten silver nitrate did not register a charge on the ammeter.
Disposal of silver nitrate solid: I have collected silver nitrate solution in a winchester and decanted it off, ready to evaporate the solution, so that I am left with just the solid waste.