Analysis of the drop weight method

The drop weight method is an accurate yet simple technique for determining surface tension σ. It relies on dripping a liquid of density ρ at a low flow rate Q̃ from a capillary of radius R into air and measuring the combined volumes of the primary and satellite drops that are formed. The method’s origin can be traced to Tate, who postulated that the volume Ṽideal of the drop that falls from the capillary should be given by ρgṼideal=2πRσ, where g is the gravitational acceleration. Since Tate’s law is only an approximation and the actual drop volume Ṽf