desired property leading to its use. Magnesium has many uses. It offers advantages over other structural materials such as aluminium, but magnesium's usage is hindered by its flammability. Magnesium is often alloyed with aluminium, zinc and manganese to increase it strength and corrosion resistance. Magnesium has many other industrial applications, such as its role in the production of iron and steel, and in the Kroll process for production of titanium. Calcium is used as a reducing agent in the separation of other metals such as uranium from ore. It is a major component of many alloys, especially aluminium and copper alloys, and is also used to deoxidize alloys. Calcium has roles in the making of cheese, mortars, and cement. Strontium and barium have fewer applications than the lighter alkaline earth metals. Strontium carbonate is used in the manufacturing of red fireworks. Pure strontium is used in the study of neurotransmitter release in neurons. Radioactive strontium-90 finds some use in RTGs, which utilize its decay heat. Barium is used in vacuum tubes as a getter to remove gases. Barium sulfate has many uses in the petroleum industry, and other industries. Radium has many former applications based on its radioactivity, but its use is no longer common because of the adverse health effects and long half-life. Radium was frequently used in luminous paints, although this use was stopped after it sickened workers. The nuclear quackery that alleged health benefits of radium formerly led to its addition to drinking water, toothpaste, and many other products. Radium is no longer used even when its radioactive properties are desired because its long half-life makes safe disposal challenging. For example, in brachytherapy, short half-life alternatives such as iridium-192 are usually used instead. Representative reactions of alkaline earth metals Reaction with halogens Ca + Cl2 → CaCl2 Anhydrous calcium chloride is a hygroscopic substance that is used as a desiccant. Exposed to air, it will absorb water vapour from the air, forming a solution. This property is known as deliquescence. Reaction with oxygen Ca + 1/2O2 → CaO Mg + 1/2O2 → MgO Reaction with sulphur Ca + 1/8S8 → CaS Reaction with carbon With carbon, they form acetylides directly. Beryllium forms carbide. 2Be + C → Be2C CaO + 3C → CaC2 + CO (at 2500 °C in furnace) CaC2 + 2H2O → Ca(OH)2 + C2H2 Mg2C3 + 4H2O → 2Mg(OH)2 + C3H4 Reaction with nitrogen