Dehydration is usually carried out by transferring the tissue through solutions of increasing alcohol concentration, until 100% alcohol is reached. Sometimes the first step is a mixture of formalin and alcohol. Other dehydrants can be used, but have major disadvantages. Acetone—though fast—is a fire hazard, so it is safe only for small, hand-processed sets of tissues. Dioxane can be used without clearing, but has toxic fumes.
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