What must be done when assembling the distillation apparatus to prevent the loss of vapor?

Applying vacuum grease to all of the joints is essential when assembling the distillation apparatus to ensure an airtight seal. This prevents the loss of vapor during the distillation process, which is crucial for achieving efficient separation and collection of the distilled components. Without a proper seal, vapor can escape, leading to inaccurate results, loss of product, and potential safety hazards due to the release of volatile substances.

Vacuum grease fills in any gaps or imperfections between the glass joints, preventing leakage that could compromise the system's integrity. This step is particularly important in a vacuum distillation setup, where maintaining low pressure is essential for distilling substances at lower temperatures.

While sealing the flask with a lid or using a secondary condenser might seem beneficial, they do not address the fundamental requirement of ensuring that all connections are airtight and well-sealed. Continuous cooling is important during distillation, but it alone cannot prevent vapor loss if the apparatus is not assembled properly. Therefore, the application of vacuum grease is the most effective and necessary measure to prevent the escape of vapor during the distillation process.