Sentence:  For the low-temperature measurements the sample was cooled by a cold <WSD>nitrogen</WSD> gas flow method similar to that of Andrew and Eades . 
Meaning of the word marked with <WSD> tags:  a common nonmetallic element that is normally a colorless odorless tasteless inert diatomic gas; constitutes 78 percent of the atmosphere by volume; a constituent of all living tissues