Mercury is removed from crude oils, natural gas condensates and other liquid hydrocarbons by first removing colloidal mercury and solids that contain adsorbed mercury and then treating the hydrocarbons with an organic or inorganic compound containing at least one sulfur atom reactive with mercury. The inductor comprises a first number of electrically conductive tracks in, or on, a substrate. The continuously variable transmission 50 has an input shaft connected to the rotating shaft 24 and an output shaft connected to the driveshaft 22 via a gear mechanism 52. When the detecting device 3 detects a reduction in the remain in the ink containing portion 16, ink remains only in the negative pressure generating member containing portion 14 and the remainder can be substantially estimated.