In this task, you are given a question and a context passage. You have to answer the question based on the given passage.
Q: What temp is the hydrogen purified by?, Context: Hydrogen is highly soluble in many rare earth and transition metals and is soluble in both nanocrystalline and amorphous metals. Hydrogen solubility in metals is influenced by local distortions or impurities in the crystal lattice. These properties may be useful when hydrogen is purified by passage through hot palladium disks, but the gas's high solubility is a metallurgical problem, contributing to the embrittlement of many metals, complicating the design of pipelines and storage tanks.
A:
hydrogen is purified by passage through hot