The reaction flask is usually made of thick glass and they can tolerate large pressure differences, with the result that you can keep two both in a reaction under vacuum, and pressure, sometimes simultaneously.
Labu reaksi biasanya terbuat dari kaca tebal dan mereka dapat mentolerir perbedaan tekanan yang besar, sehingga dapat menahan keduanya dalam reaksi di bawah vakum, dan tekanan, terkadang bersamaan.