The rapid formation of drops of viscous liquids

Earlier dimensional analyses which established a relationship between the weight W 0 of a very slowly formed (`static') drop and surface tension have been extended to rapidly formed drops of viscous liquids. ΔW/γR would be expected to be a function of R 2 ρg/γ and η W /γ 2 where Δ W is the increase over the `static' drop weight when the weight rate of flow is W from an orifice of external radius R. Here ρ, γ and η represent the density, surface tension and viscosity of the liquid. A further assumption leads to the conclusion that Δ W/W 0 should be a function of η W /γ 2 only. These predictions are verified for a single orifice and less satisfactorily when the orifice size is varied. The results permit the application of the drop-weight method for measuring surface tension to viscous liquids for which the time taken to achieve a true `static' drop weight would be excessive.