pendant-drop tensiometer

1. n. [Enhanced Oil Recovery]
A standard laboratory instrument used to measure interfacial tension. The method is particularly applicable to relatively high interfacial tensions, but with care can measure down to approximately 1 mN/m. A drop of the denser liquid is poised at the end of a square-ended syringe needle. The drop is of sufficient size that its shape is deformed by gravity, but not so large that it detaches from the syringe. Its shape is determined by the balance of interfacial tension and gravity. The interfacial tension can be obtained from the drop shape and the densities of the two liquids. The method works equally well for a drop of the less-dense liquid by inverting the syringe. This inverted configuration can be useful if the less-dense liquid is opaque.