By cooling the reaction mixture to room temperature, crystals of the porphyrin precipitate, and are collected by filtration on a Büchner filter as illustrated by the photograph here beside: Precipitation may also occur when an antisolvent a solvent in which the product is insoluble is added, drastically reducing the solubility of the desired product.
The compact mass obtained so is sometimes referred to as a 'pellet'.
Precipitation is always fresh water, even when the water originated from the ocean.
If they freeze, it can be hail or snow.
It forms when very cold water droplets freeze, or turn solid, as soon as they touch things like dust or dirt.
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