OXYGEN (O)Oxygen was discovered by a British chemist, Joseph Priestly in 1774, and independantly by Carl Wilhelm Scheele, a Sweedish chemist. Oxygen has many uses – it is used in welding torches, to assist in hospital patient’s breathing and in metal fabrication industries. Oxygen is also used for defense purposes as a propellant for guided misiles and rocketsCARBON DIOXIDE (CO2).Carbon dioxide was named ‘fixed air’ by a Scottish chemist, Joseph Black. A French chemist, Antoine Lavoisier proved that ‘fixed air’ is an oxide of carbon, by showing that the gas obtained by the combustion of charcoal is identical in it’s properties with Black’s ‘fixed air’. Carbon dioxide is use in the manufacture of many chemicals, such as sodium bicarbonate. In society, the gas is used in fire extinguishers and as a refrigerant.