The electrical resistance of moisture films on glazed surfaces

The research described is in two parts, the first dealing with the relations between surface resistivity, humidity and temperature, and the second with the influence of gas pressure, both having for their object the discovery of the laws of film formation under controlled conditions. The first let to an expression of the form, ρ8= ρ8(d)ek(1-pa/p8)2, where ρ8(d)is the surface resistivity immediately before dew point is reached, pa the acutal vapour pressure to produce a desired humidity, and p8 that required to saturate the air at the same temperatute. The second part proves that the all humidities there is a very sharply defined critical pressure above which the resistivity falls as the pressure rises, and below which both fall together. Expressions are found for the variation of the thickness of the film and for the influence of temperature on resistivity.