zone: (a) retreating meniscus; (b) advancing meniscus.

At very low flow rates, the Pe values tend to 0, and in accordance with Eq. (8) the ratio Cm/C0 tends to 1. Respectively, the dynamic surface tension of the meniscus γm approaches the value of the surface tension of bulk solution γo. Fig. 4 shows that the surface tension of the meniscus, γm=33 mN/m at v≈0, does not differ much from the bulk value, γo=31 mN/m.