Methylamines are produced commercially by the catalytic alkylation of anhydrous ammonia with methyl alcohol. The synthesis of methylamines from carbon monoxide, hydrogen and nitrogen over a zirconium-based catalyst and the hydrogenation of hydrogen cyanide have attracted interest but both routes are still under investigation. Mono-methylamine is obtained overhead by distillation in a second column, and di-methylamine can be separated from high boiling impurities by further distillation in a third column. The same catalysts are used as for the methyl alcohol reaction, with the proportions of the three methylamines formed controlled by the volume of excess ammonia used. The reaction takes place at around 450°C and the mixture formed is cooled prior to entering a rectifier. Methylamine vapour is a severe irritant to eyes, nose, throat and skin. It can cause conjunctivitis, oedema of the lungs and dermatitis. All personnel working with methylamines must always wear protective clothing, goggles, gloves, gauntlets, aprons and boots.