Some articles on liquefying:

Michael Faraday - Scientific Achievements - Chemistry
... Faraday succeeded in liquefying several gases, investigated the alloys of steel, and produced several new kinds of glass intended for optical purposes ... (which he called bicarburet of hydrogen), and liquefying gases such as chlorine ... The liquefying of gases helped to establish that gases are the vapours of liquids possessing a very low boiling point, and gave a more solid basis to the concept of molecular aggregation ...