Alcohol is used during the gram staining procedure to decolorize the sample after it has been dyed with crystal violet. After the sample has been dyed with crystal violet, it is rinsed with water and then treated with an iodine solution, which serves as a mordant to help the crystal violet dye bind to the bacterial cell walls. The sample is then rinsed again and treated with a decolorizing solution, which typically contains alcohol. The alcohol in the decolorizing solution helps to remove the excess crystal violet dye from the sample, resulting in the decolorization of the sample. This step is important because it allows for the differentiation between Gram-positive and Gram-negative bacteria based on their different responses to the crystal violet-iodine staining.