Note 72 — Chapter VI · TTHE COMPOUNDS OF NITROGEN WITH HYDROGEN AND OXYGEN

Liquid nitrous oxide, in vaporising at the same pressure as liquid carbonic anhydride, gives rise to almost equal or even slightly lower temperatures. Thus at a pressure of 25 mm. carbonic anhydride gives a temperature as low as -115°, and nitrous oxide of -125° (Dewar). The similarity of these properties and even of the absolute boiling point (CO2 + 32°, N2O +36°) is all the more remarkable because these gases have the same molecular weight = 44 (Chapter VII.)