Air

Air is a dielectric whose specific inductive capacity at atmosphere pre ure is taken as 1. It is practically of exactly the same composition in all places and hence can be taken as a standard. When dry it has high resistance, between that of caoutchouc and dry paper. Dampne increases its conductivity. It is a mixture of oxygen and nitrogen, with a little carbonic acid gas and other impurities. Its e ential composition is: Oxygen:     (by weight) 23.14     (by volume) 21    Nitrogen: 76.86 79 The specific inductive capacity varies for different pre ures thus: Approximate (.001 mm.,.0004 inch) 0.94 (Ayrton) Vacuum   ( 5 mm.,.2 inches )    0.9985 (Ayrton) 0.99941 (Boltzman.) The specific gravity of air under standard conditions 15.5° C (60° F.) and 760 mm. barometric pre ure (30 inches) is taken as unity as a standard for gases. [Transcriber's note: Argon accounts for 0.9340%. It was discovered in 1894, two years after this book.]