How many times is cleaning xylene pumped in and out of the retort during maintenance?

The correct answer, which states that xylene is pumped in and out of the retort during maintenance nine times, is based on the standard procedure for ensuring thorough cleaning and effective maintenance of the retort. Pumping xylene this specific number of times allows for the complete removal of any wax and debris that may have accumulated inside the retort, which is critical for maintaining the integrity of the samples during further processing. This number is chosen to ensure that the solvent properly flushes the system and ensures that all surfaces are adequately cleaned.

The exact number of times xylene is cycled in and out can depend on established laboratory protocols or manufacturer guidelines, often reflecting best practices in laboratory maintenance. This level of detail in cleaning is essential because inadequate cleaning can lead to contamination of future samples, which is a significant concern in laboratory settings. Thus, the specific figure of nine times represents a well-researched balance between efficiency and thoroughness in retort maintenance protocols.