# Why is it necessary to wash silver chloride before drying it?

You got a slurry of insoluble $A g C l$ as a white solid. The curdy precipitate can occlude some other halide salts UNLESS you give it a good wash with water. And of course here you face the problem that the silver chloride is photoactive, and could photo-reduce to silver metal. And this used to be basis of old black and white photography.