Probably not if you work in a routine laboratory – but it can be important if you work in a research laboratory where this type of fixative is more commonly used to fix and enhance particular structures. Prolonged washing is also required after both - to remove the dichromate from Zenker and the picric acid from Bouin's which makes both unsuitable for a busy routine laboratory.

Why is the next question and the answer is because most mucosubstances are hydrophilic and can be denatured by aqueous fixatives like Zenker and Bouin's.

The most effective method of fixation for all mucosubstances is any of the alcoholic fixatives that have been pre-cooled to below -50°C. The snap frozen tissue can then be allowed to thaw to room temperature in the fixative. Hydrophilic structures, like mucosubstances, are thus immobilised within the tissue for subsequent processing like dehydration, clearing and embedding.