In a spray column, a liquid is sprayed into a gas stream, and mass is transferred between the liquid and gas phases. The formation of liquid drops from the spray nozzle is considered to be a function of the nozzle diameter, gravitational acceleration, surface tension of the liquid against the gas, liquid density, liquid viscosity, velocity, and the viscosity and density of the surrounding gas medium. Arrange these variables into dimensionless groups. Should any other variables have been included?