Quick Answer A quartz flask is a high-purity fused silica vessel with a neck. The neck is the point. It takes a stopper, a ground joint, a condenser, or an inert-gas line, so the contents can be heated, refluxed, distilled, or held under vacuum without the open-top losses of a beaker. It is not a quartz beaker. A beaker is for open heating, mixing, and pouring. [...]