New material has been added to this edition, including entirely new topics, such as electron inelastic mean free paths
, proton affinities, vapor pressures (solvent activities) for binary polymer solutions, selected properties of semiconductor solid solutions, and electrical conductivity of aqueous solutions.
A summary of these studies and the resulting mean free paths is reported by Allen and Raabe  who fully re-evaluated the Millikan oil drop results by least square fitting the data using a mean free path of 67.
This assumption begins to break down for particle diameters several times the gas mean free path when such particles experience "slip" at their surface.
lambda] = mean free path in the liquid or gaseous phase
While there are analytic expressions for the slip correction in the limit of particle size large compared to the mean free path (Stokes) and small compared to the mean free path (Epstein), there have not been quantitative calculations for the intermediate region.
Using the Cunningham correction factor, application of Stokes law can be extended to the particle sizes comparable to or less than the mean free path of the gas molecules.
It is important when comparing the values to use the same mean free path for air at standard conditions.
Before describing the experimental approach, we first present the key fluid properties for computing the slip correction factor, the viscosity and the mean free path.