An apparatus (10) and method for down hole gas separation (18) from the multiphase fluid (16) flowing in a wellbore or a pipe, for determining the quantities of the individual components of the liquid and the flow rate of the liquid, and for remixing the component parts of the fluid after which the gas volume may be measured, without affecting the flow stream, are described. Acoustic radiation force is employed to separate gas from the liquid, thereby permitting measurements to be separately made for these two components; the liquid (oil/water) composition is determined from ultrasonic resonances (32); and the gas volume is determined from capacitance measurements (44). Since the fluid flows around and through the component parts of the apparatus, there is little pressure difference, and no protection is required from high pressure differentials.