On a particular day the atmospheric air was found to have a dry bulb temperature of 30°C and a wet bulb temperature of 18°C. The barometric pressure was observed to be 740 mm Hg. Using the tables of psychrometric properties of air, determine the relative humidity, the dew-point temperature, the partial pressure of vapour, the enthalpy of air per kg of dry air and the volume of mixture per kg of dry air.