The Determination of Arc Temperature from Sound Velocity Measurements. II

Abstract

Experimentally determined values of the velocity c of sound in atmospheric pressure arcs in air are interpreted in terms of the temperature of the gas. The velocity may be expressed in general in the form: $${\text{c=((RT/M)(1+R/C}}_v{\mathrm{))}}^{\frac{1}{2}},$$ which applies to pure gases or mixtures of gases that obey the perfect gas laws. In this relation T is the absolute temperature; M is the mean molecular weight defined as: M=ΣM_ip_i/Σp_i; C_v is the specific heat (per gram molecule) defined as: C_v=Σ(C_v)_ip_i/Σp _i, where the summation is taken for all the gas components present. In the case of the arc in air, the components considered are the undissociated and dissociated oxygen and nitrogen. The values for the specific heat and degree of dissociation, taken from the equilibrium calculations of H. L. Johnston and associates are used, care being taken to apply the correct partial pressures. Possible sources of error due to thermal diffusion and other causes are considered.