How it began
Alan Walsh, a Lancashire-born physicist at the CSIRO Division of Chemical Physics, had long worked on how to measure small concentrations of metallic elements more exactly. On a Sunday morning in March 1952, while gardening at his home in the Melbourne suburb of Brighton, he realized that the measurement should be of absorption, not emission. He phoned his colleague John Shelton, and on Monday morning set up a simple experiment using sodium. By morning tea he had a successful result.
Before it existed
The normal procedure in spectroscopy was to vaporize an element and measure the energy emitted as light by its excited atoms. Flame emission spectroscopy of this kind detected only seven or eight elements, because even in the hottest laboratory flames very few atoms reach the excited state.
How it works
All atoms in their normal state can absorb light, so measuring absorption is generally much more sensitive than measuring emission. Walsh's device used a burner flame to turn a sample solution into atomic vapor. A lamp of the element being measured shone through the flame, and a detector on the other side picked out that element's light frequency. The amount of lamp light absorbed by atoms in the flame showed how much of the element the sample contained.
How it spread
Twenty licenses had been issued by the time the original patents expired around 1969. Sales grew very quickly between 1963 and 1967. By 1969 more than 10,000 atomic absorption instruments were in use in hospitals, factories and laboratories, and by 1977 about 40,000.
Who pushed back
CSIRO records that Walsh's discovery met almost universal indifference for years. The head of a large American corporation challenged him, asking why the technique was not in use in the United States if it was so useful. That corporation later became the largest manufacturer of atomic absorption equipment.
What lasted
The method can determine the concentrations of over sixty-five elements and is used in medicine, agriculture, mineral exploration, metallurgy, food analysis and environmental monitoring. CSIRO credits its commercialization with starting the scientific instrument industry in Australia. A 1968 cost-benefit study valued the net benefit to the Australian economy at about 22 million dollars against 1.3 million spent on the research, with most of the gain going to users of the method.
