Effects of pulsed and static magnetic fields on surface tension measurement by drop volume method

In a surface-tension measurement of a solution by a drop volume method, a magnetic force was applied by a pulsed electromagnet (< 15T) and a static permanent magnet (0.55T) in order to investigate the effect of a magnetic force. In the drop volume method, a drop of MnCl2 solution was formed at the end of a glass capillary that had 0.73 mmo in outer diameter, using a syringe pump. From the droped volume of the aqueous solution, the surface tension was measured. When a magnetic field gradient was applied to the droplet formed at the capillary end, a smaller droplet was droped than that of the volume in the absence of a magnetic field. In case of a static magnetic field, the effect was well explained by the magnetic gravity force added to the original gravity force. On the other hand, a pulsed magnetic force of 0.43 ms or 0.80 ms was not enough to make the drop fall, because the pulse duration was too short to pull down the droplet. This result required the introduction of an effciency factor of 0.01 similar to 0.97, depending on the pulse duration and the magnetic susceptibility of the sample solution. Furthermore, the pulsed magnetic-field experiment allowed to esitimate the relaxation time of a droplet as being 7.8 ms, which implied that the magnetic filed had to continue for at least this time to be droped. Based on the present study, it has been suggested that a simultaneous measurment of surface tention and magnetic susceptivility was plausible by using a drop-volume method under a static magnetic field, or a pulsed magnetic field.