Gas analysis

Which one of the following gases is paramagnetic?

a) Nitrogen

b) Nitrous oxide

c) Nitric oxide

d) Nitrogen dioxide

e) Dinitrogen tetroxide

Answer: c

Explanation

The only paramagnetic gases used in anaesthesia and intensive care are oxygen and nitric

oxide. The application of this principle is used in the paramagnetic oxygen analyser – the

concentration of oxygen in a mixture of gases may be measured regardless of the other

constituents of the mixture (providing one of them is not nitric oxide). The same cannot

be said of other methods of gas analysis where reliability is impaired with particular

constituents of a gas mixture. Some of the other gases in the question are higher oxides

of nitrogen produced as byproducts in the manufacture of nitrous oxide. They must

be removed before supply of nitrous oxide as they have serious toxicity if inhaled.