Thaumcraft 5 Wikia

Glass Phials are both an introductory research found under Alchemy tab and an item. Glass Phials are created with 3 glass and a piece of clay in crafting table or Arcane Workbench as one would glass bottle, but with a piece of clay now in the middle section of the crafting grid. This yields 8 Phials at a time. The Phials can be used to transport batches of 8 Essentia at a time, and can be stacked up to 64, when either empty and full of Essentia, and are also used in some crafting recipes, and can also be used to mark Labels, Filtered Essentia Tubes, and other related items. They're also a good source of the aspect of Vacuous, and, when full of Essentia, can be good sources of aspects for Alchemy, being relatively precise and only offering the aspect contained in the phial, as opposed to the Vacuous aspect contained by the empty phial.

The crafting recipe for the Glass Phials as shown in the Thauminomicon. Please note and excuse the use of a texture pack.