nitrogen

Nitrogen is a relatively inert gas added to some beers in order to create very fine bubbles and foam, and a creamy feel. Nitrogenated beers are typically pressurized (to dissolve gases into the liquid) and propelled with a mix of nitrogen with CO2 at a ratio of 70 to 30 percent. Nitrogenated beer was created in the 1950s by Arthur Guinness as a way of replicating the smooth feel of cask beer.