Protein precipitation is a very crude method for purification and it rarely achieves enrichment by more than a factor of 2–3. However, it is quick and cheap. If applied to crude homogenisates, it may remove material that would interfere with later purification steps. It is essential to perform these reactions in the cold because proteins are rapidly denatured by precipitating agents at room temperature. Mixtures of ice and salt are more effective in keeping samples cold than cold rooms, which only chill the scientist.