75% alcohol has no residue after evaporation, usually 75% alcohol belongs to medical alcohol, the formula of medical alcohol is ethanol and distilled water, these two substances can be completely evaporated into the air, so there is no residue after evaporation. 75% alcohol is usually used for skin or object surface disinfection work, you can also pour it into the spray bottle for air spraying, air disinfection, because water and alcohol are volatile and easy to evaporate substances, and in the evaporation will not remain on the object or the surface of the object. As both water and alcohol are volatile and evaporable substances, and when evaporated there will be no residue on the surface of the object or skin, so you can use 75% alcohol to kill the skin surface, air and objects without worrying about the harm brought by alcohol residue, because there is no residue after evaporation of 75% alcohol.