Readers sniff out some chemicals and share how they would respond in an emergency

Support in South Africa

The statistics collated by the Royal Society of Chemistry Inclusion and Diversity Group on the progression of Black chemists in the UK has brought into focus the incredible support the society gave to Black students in South Africa some years ago.

Our local section in Johannesburg received substantial donations from Burlington House to provide hundreds of textbooks, periodic tables and other teaching aids for schools in the townships, as well as tremendous encouragement from the society presidents and staff. A hands-on periodic table was built for the much used local science museum and a chemistry bus toured dozens of Soweto schools demonstrating chemistry experiments and supporting educators who had previously had very few tools to help them teach the subject.

Universities were provided with a range of books and prominent academics were encouraged to visit, give lectures and attend society-supported conferences. Local companies provided bursaries with extensive mentoring for both undergraduate and postgraduate students as well as financial support for new and established academic staff.

While current circumstances in the UK are obviously different, we learnt that using local expertise to determine what was needed and providing on-point resources and support was the best way of helping Black students negotiate the system. The strong reputation and commitment of a society with no axe to grind was crucial in getting the attention and involvement of all stakeholders, including local and national government.

Mike Green FRSC
Newcastle, UK

Fair or foul

I found the article on ‘Godzilla’s gym socks’ rather troubling. I am not going to pretend that isocyanides are harmless (they are toxic) but the article appears to be falling into the trap of equating foul smell with high toxicity or high impact on the environment. I did my PhD on foul smelling sulfur phosphorus compounds so I have considered the lack of relationship between toxicity and attractiveness of smell.

I am one of the circa 30% of the population who can smell hydrogen cyanide. My threshold for being able to smell it is low as I have been aware of the smell when opening safes, drawers and overpacks which contain well-sealed bottles of cyanide salts. If we ignore how toxic hydrogen cyanide is (1.8ppm Swedish level limit value (LLV)) and merely rate it on how unpleasant/pleasant it is then I would judge it as being a pleasant smell, nicer than tetrahydrofuran (THF; 50ppm LLV) and far nicer than pyridine (2ppm LLV) and butyric acid. Given the choice I would rather have a trace of foul smelling medium sized carboxylic acids in the air that I breathe than either pyridine, hydrogen cyanide or THF.

I would also like to point out that there are plenty of things that are harmful to health at concentrations below that at which they can be detected by the nose. The threshold for smelling benzene for most people is between 1.5–4.7ppm, but occupational exposure limit values set by the Swedish Work Environment Authority (in AFS 2011:18) sets the workplace exposure limit for benzene at 0.5ppm for an eight-hour working day, while the UK’s eight-hour limit is 1ppm. I reason that an inability to smell 1.1ppm of benzene does not make it OK to breathe all day!

Mark Foreman CChem MRSC
Göteborg, Sweden

What’s cooking

The article on the complexity of fire reminded me of a phenomenon of which few chemists seem to be aware. At home, we cook using gas. We light the gas hob using an electric spark. If there is no pan on the hob when I switch on and I stand with my nose about 50–60cm above the gas ring then I am far enough away not to get burnt but for a second or two I can detect a distinct initial odour. For an experienced chemist it is quite unmistakeable – methanal, or formaldehyde to its friends.

The formation of methanal is not surprising. The spark is igniting a cloud of methane, mixed with only a limited air supply so the methane is only partly oxidised. In fact you need exactly the same amount of oxygen as you would to form carbon in the form of soot, but you get only half the amount of water. The smell rapidly disappears when the gas starts to burn at the ring, which is carefully designed to use optimum amounts of air. Presumably I have not observed the same phenomenon with Bunsen burners because of their different design. Back of the envelope calculations confirm to my satisfaction that the tiny amount formed transiently does not present a significant risk, but I still find it quite interesting how little known it is.

Peter Borrows CSci CChem FRSC
Amersham, UK

Good spot

The answer to On the spot only refers to the situation and not to what the teacher’s actions should be.

It might also have included ‘Reassure the class, sound an alarm and take any appropriate actions that can be safely carried out, such as turning off the gas burner and/or removing the fuel of the fire. Prepare to evacuate the room.’

Pam Day CChem MRSC
Bristol, UK

While I am sure that referring to a CLEAPSS Guide prior to a fire in the classroom might have saved the unfortunate teacher some trouble, a more serious fire might well have developed while he took time to look this up on the laptop on his desk. Since he is heating a liquid in an open beaker and not in a fume hood, one might assume that the liquid is aqueous and pretty innocuous and could thus be used for putting out the fire.

But most of us would agree that paperwork is a hazard if not always of an incendiary nature!

Peter Baker CChem FRSC
Prestwood, UK

Making ammonia

James Mitchell Crow reviews current practice in ammonia synthesis. He explains how we consume fossil fuels and oxygen to make ammonia. Arguably though this is outdated thinking. Nature makes ammonia under ambient conditions in the presence of moisture and oxygen in leguminous plants from its elements in poor quality water.

In the brave new world that we are struggling to embrace we are trying to learn how to work with the planet. Perhaps it would be more sustainable to consider how to supply the developing and developed regions with annual, ample supplies of these legumes so that the local populations can be engaged in the struggle to generate ammonia.

Clive Delmonte FRSC
Fakenham, UK


The review of What Stars are Made of: The Life of Cecilia Payne-Gaposchkin (Chemistry World, September 2020, p65) stated that the University of Cambridge first awarded degrees to women in 1925. In fact, this did not occur until 1948.


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