Nitrous oxide. Molecular model of the chemical compound nitrous oxide (N2.O). This colourless non-flammable gas is used in surgery and dentistry for its anaesthetic and analgesic effects. It is known as laughing gas due to the euphoric effects of inhaling it, a property that has led to its recreational use as a dissociative anaesthetic. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue) and oxygen (red). Illustration.