LAUSR

In the century following its discovery, oxygen was largely produced by the thermal decomposition of various chemical compounds. Such endeavours were costly, owing to the large volume of raw materials and high temperatures required, and the small quantities of oxygen produced were often contaminated with high levels of impurities. As early as 1798, JeanAntoine Chaptal noted, ‘I have uniformly observed that the use of oxygen gas, evolved from the mercuric oxides, produces salivation, at the end of a few days’ use’. In addition, many of these reagents were potentially dangerous: ‘An English pharmacist, in preparing oxygen from the peroxide of manganese, was severely wounded by the explosion of the retort in which it was being manipulated, a pupil who assisted him being killed by the accident. An analysis of the peroxide . . . showed that it contained a considerable quantity of charcoal, which, by its rapid combustion in the gas, had caused the explosion’. By the early 1860s, it had become clear that potassium chlorate was ‘the substance which most readily yields the whole of its oxygen’ when heated in the presence of the catalyst manganese dioxide. The addition of a small amount of ferrous carbonate served as a safeguard against the evolution of chlorine gas. The oxygen produced by this reaction was suitably pure, and the price of potassium chlorate sufficiently low, that several small companies began to exploit the technique commercially. While most of gas they produced was destined for theatres and music halls, where it was employed in the production of limelight (an intense light created by directing an oxyhydrogen flame at a cylinder of quicklime), a handful of individuals focused their attention on the production, storage and distribution of oxygen for medical use. In 1864 in Paris, Stanislas Limousin constructed ‘an ingenuous and convenient apparatus for preparing oxygen’ which could be ‘easily and economically arranged in any drug-store or pharmacy’. Cover photo. Foregger Autogenor. Courtesy of the Wood-Library Museum, Schaumburg, Illinois, USA.