Inside the Collection

Flash of insight led to brilliant Australian invention

Atomic absorption spectrophotometer
Atomic absorption spectrophotometer. Powerhouse Museum Collection.

Dr Alan Walsh had an ‘aha’ moment while gardening in 1954. Straight away, he phoned a friend and said: We’ve been measuring the wrong bloody thing! A CSIRO chemist, he wasn’t referring to delphiniums (blue) or geraniums (red). He was thinking about atoms that emit characteristic colours when heated in a flame – elements such as strontium (red) and selenium (blue).

At that time, the concentration of certain atoms in a sample was determined by measuring the amount of light the sample EMITS when heated in a flame. He realised it would be better to measure how much light of a particular colour (wavelength) the sample ABSORBS. He thought his ‘atomic absorption’ method would be more accurate than the emission method.

Now Walsh had been thinking about this problem off and on for years. In his ‘aha’ moment he realised it was possible to get around the major stumbling block: the need to filter out the emitted light so it didn’t swamp the measuring device.

Walsh soon set up an experiment to test his ideas. It worked brilliantly. With the help of other scientists and technicians, he designed a new type of lamp containing the element to be measured. His technique did prove to be more accurate than the old method – and it was more sensitive, and useful for many more elements. His work led to the creation of a local industry making atomic absorption spectrophotometers (AAS). It also led to scientific and practical advances in many fields as CSIRO scientists developed new techniques and labs around the world purchased the instruments.

One of these instruments was offered to the Museum a few years ago by Tim and Kylie Bennett from Alstonville in northern NSW. They were planning to upgrade to a new AAS for their analytical service lab, and the donation of their old one was very welcome. They told us its original owner was the University of New England, where it had been used for studying domestic ruminant physiology.

Now that more information is available online, it appears highly likely that the ruminants studied were sheep and the instrument was used to show (among other things) that they need copper and zinc in their diet to grow good quality wool. A nice connection to our wool and textile collections!

More information is also available about the work of the Bennetts’ company, Soiltec. As its name suggests, it was involved in analysing agricultural soils, but it also analysed plant material. This work was largely aimed at helping farmers grow crops without adding unnecessary quantities of fertiliser to the soil. A nice connection to our sustainability theme!

Making connections is a vital role for museums. These include connections between objects and ideas; connections between disparate objects; connections between objects and images; and, most importantly, connections between objects, ideas and people. I hope my chemistry-themed blog posts for the International Year of Chemistry have made some interesting connections for you.

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