During the process of potein crytalization may salts are present in the buffer we use.........now when these salts can also form crystal.how is say which is a protien crystall and which one is a salt crystal(prior to x-ray diffraction study)?
One way is to use the "Izit" crystal dye from Hampton Research.
You can also do the "snap test". Salt crystals are hard and if you crush them with a needle or micro tool you can ofter hear them "snap". Protein crystals are really soft and the needle will easily break them up and they won't snap. This is pretty reliable once you gain some experience with the snap test.