Readers discuss prospecting, chirping and cracking

A real gem

The articles by Andrea Sella on historic aspects of chemistry are always highlights of Chemistry World. Perhaps it is because I learned my chemistry at a time when many of the items he describes were still in use. Regarding the early discoveries around light polarisation, I was always enchanted by a large crystal of Iceland spar (calcite) in the museum at Canterbury. Two images produced from one object seemed like magic. A few years ago I found an old book The Prospectors Handbook, no doubt an essential guide to prospectors seeking to make a fortune in the New World. As well as having tables to calculate the horsepower of water wheels, it introduced me to the dichroscope for detecting chirality in minerals and gemstones. Based on a calcite crystal, it is a very handy gadget for discriminating between gems and paste, glass being anisotropic.

Also in the prospector’s toolkit was a direct vision spectroscope. I have several, my favourite being labelled ‘Rain Band Spectroscope’. It was an aid to weather forecasting before the days of national weather forecasts. It worked by the examination of weak absorption bands, caused by water vapour, in the red part of the spectrum. I use it primarily to detect lanthanide elements in glass. Specimens containing neodymium exhibit striking colour changes when examined with white light from different sources. Armed with a few historical chemistry tools, the world of antiques is ideal for the scientifically inclined to seek out treasures which are invisible to the casual observer.

Perhaps Sella could feature the etalon filter in a future article. It enables solar prominence to be seen by viewing the solar disc in the H alpha spectral line. Now that really is magic!

Michael Baldwin CChem FRSC
Sittingbourne, UK

Chirp away

The morse background on Donna Strickland’s picture connected with her liking for British police dramas is ironic when we consider her Nobel prize. I have held an amateur radio operators license (G7LSZ + SA6BID) for years; part of the territory which comes with this is a knowledge of how to build radio gear and other aspects of radioelectronics. Chirping is when the frequency of a pulse changes as a function of time. While chirping a laser pulse assists the amplification process and I know that some animals use chirped sound pulses in their sonar, it is not always welcome. In radio transmitters for morse service it is normal to want to make the spectral width of the pulses (dots and dashes) as narrow as possible, so chirp is considered to be a defect. The classic cause would be a supply voltage change caused by the current drawn by the radio frequency power amplifiers causing the frequency of the transmitter to change.

Mark Foreman CChem MRSC
Gothenburg, Sweden

Full support for part-time

I read the letters relating to part-time qualifications with some interest. I owe my interesting and varied career to the solid grounding in chemistry gained from part-time study alongside a full-time job. I too qualified by part-time study leading to a Grad RIC in 1976.

I left the Hull Technical College with A-levels in chemistry, physics and maths and joined Reckitt and Colman in their household division labs. They actively encouraged day release to the Technical College. I did ONC chemical, physics and maths courses then HNC chemistry and physics. I then had a period where I ran a small machine and hand tool engineering business with my father and a colleague while continuing my part-time studies for Grad RIC parts 1 and 2.

After a couple of years I became a technician in the physical chemistry department at Hull University where I worked on gas kinetics and over a two-year period gained my MSc by attending part-time study courses and submitting a thesis. As I was finishing this I applied for a job as an experimental officer at the University of Kent. I was again allowed to develop this work into a PhD thesis, which I successfully submitted at the end of the contract period.

Towards the end of the contract I met Dot, a biochemistry technician who was also doing her MSc. We married and moved up to Hull after I applied for a job in the development department at the BP Salt End Chemicals plant. During the interview I was asked if I thought my Grad RIC and part-time qualification route was as good as the full-time courses of the London, Oxford and Cambridge universities that most of that year’s graduate intake seemed to be from. I replied that I thought mine was actually better as I had the benefit of a wider range of real-life on-the-job training and techniques, as well as the theoretical knowledge.

During my time at BP I successfully applied for both Chartered Chemist status and the accolade of FRSC. I am now retired, but still hold that my early training through part-time study alongside real day-to-day application of practical chemistry in working laboratories gave me a set of skills and a mindset that is difficult to gain in a purely academic setting.

Mike Clarke CChem FRSC
Castle Hedingham, UK

Cracking process

I would like to amplify the merits of the pyrolysis of methane as set out in the recent letter by David Greenslade. Summing up the input energy to heat methane to 1000°C and the dissociation energy to form carbon and hydrogen, with the energy released from combustion of that hydrogen, a surplus energy of over 400kJ is produced per mole of methane. So energy has been produced from methane without creating any carbon dioxide. That must compare very favourably with any other means of producing hydrogen.

Steam reformation requires carbon dioxide to be disposed of in deep geological strata. It makes us hostages to geological fortune whereby a massive release of carbon dioxide occurs in the future. Note the catastrophic release of carbon dioxide from Lake Nyos in Cameroon in 1986 that killed some 1700 people.

Roger Newman CChem FRSC
Dursley, UK

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We incorrectly labelled alpha-linolenic acid as alpha-linoleic acid in the article on Omega-3s (Chemistry World, February 2023, p51). Thanks to Peter Halls for bringing this to our attention.