1 the temperature is selected such that upon cooling to a common temperature
设定温度在冷却温度至常温之间。(温度的设定 /选择应该是个范围,这样表达比较好)
2 each element is chosen such as to form a compound with hydrogen in the ionised gas
选定的每个元素可以与电离气体内的氢形成化合物(两句可以放在一起,如果把such as to 按字面意思表达出来,就比较生硬,按中文的意思翻成可以就可以搞定了,普通技术人员都能理解明白)