From chemistry stats to chemistry sets
I enjoyed reading Mike Sutton’s article ‘Is all matter made of just one element?’.
My particular interest is in Henry Moseley, who was killed in action at Gallipoli 100 years ago on 10 August 1915. Many textbooks state, incorrectly, that Moseley discovered atomic number, an impression I gathered from the article. Moseley identified a property (the wavelength of the x-rays emitted by a metal when bombarded by high energy electrons) that is directly related to the serial number of the element in the periodic table. In his eighth and last paper published in 1914 in the Philosophical Magazine he called this property atomic number, a term used the year before by Ernest Rutherford. Part of this confusion stems from identifying the originator of concepts by people working in closely related fields, after all Moseley had been a member of Rutherford’s Manchester team.
It is a sobering thought that a century later school pupils are familiar with the term atomic number and its dependence on the number of protons in an atom. I believe that Moseley was the ablest Allied scientist to be killed in the first world war and would almost certainly have been awarded the Nobel prize had he lived.
G Woods FRSC
Check your stats
David Fulton’s letter quoted a statistic (no doubt sourced from media reporting) that 38% of newly qualified teachers leave the teaching profession within one year of beginning their teaching careers.
BBC radio’s More or less programme, which sets out to highlight misleading statistics, made clear on 15 May that the 38% figure quoted above is incorrect. At the Association of Teachers and Lecturers annual conference, the general secretary Mary Bousted said: ‘In 2011, the latest year for which figures are available, just 62% of newly qualified teachers … were still in teaching service a year later.’ What she didn’t make clear was that the other 38% also included any qualified teacher who had decided not to begin a teaching career; those who had taken a year out; and those who may have an education-related job that wasn’t captured in this analysis (for example, teaching in the independent sector or overseas).
As is all too common, the media read the data uncritically, flipped it around and reported that 40% of new teachers left after one year. Apparently only The Independent later admitted the error.
On More or less, Sam Freedman, director of research, evaluation and impact at the education charity Teach First, stated that the true figure is closer to 9%, based on information collated by the National College for Teaching and?Leadership.
In relation to all education matters, I’d like to encourage members to treat all data and evidence quoted by the media, unions and most importantly politicians and their quangos with appropriate scepticism.
Beneath the surface
As a recently retired chemist with 30 years’ experience as global technical director in the paint and coatings industry, I would like to add to Mike Baldwin’s correspondence regarding the phenomenon of surface tension differential driven flow (the Marangoni effect). Baldwin will, I am sure, be interested to know that this effect is widely taught to all technical newcomers in the industry to enable them to understand the film formation process of coatings during the curing process.
A lack of understanding in this area can lead to many types of film defect, including craters, eye holes and other problems, which can lead to miscellaneous problems, including corrosion of the underlying substrate and poor visual appearance, among others.
R Dyer CChem FRSC
Accentuate the negative
In his article ‘A negative outlook’, David Jones speculates on mechanisms for forming images on cellulosic substrates that are similar in appearance to photographic?negatives.
These stains on paper and textiles can often be seen on old books and dismantled picture frames. They can take many years to form and are thought to be the result of vapour-phase migration of substances from slowly off-gassing or deteriorating materials. Some of these substances are oxidants and some acids. Indeed, William Russell, a past president of the Chemical Society, is best known for his 1860s work on the evolution of hydrogen peroxide from wood, oxidising drying oils and varnishes. In the long term, hydrogen peroxide produces carbonyl groups in cellulosic materials, which leads to discoloration. Similarly, acid-catalysed degradation of paper can cause discolouration.
This problem is a major concern for museum conservators who only use carefully tested products so that they may avoid discolouration and deterioration on precious objects. Consider the case of a head wrapped in a textile: the parts closest to the textile are normally best illuminated as they are most prominent; the textile in these areas suffers the greatest discoloration and dark recesses suffer less. The result is a negative image.
V Daniels FRSC
The joy of sets
Philip Ball’s article ‘All set for chemistry’ was certainly evocative for those of us of a certain age. However, it did seem to have an undue emphasis on US chemistry sets. When I was knee-high to the proverbial, Merit (J&L Randall) or Lott’s were the predominant suppliers in the UK with some other, less conspicuous brands.
My own chemical odyssey was initiated by watching my elder brother’s experiments – he had both Lott’s and Merit sets at various times and I still have his old coal-gas Bunsen! I later acquired mostly Merit outfits myself, further augmented by equipment and chemicals from local pharmacies and mail-order suppliers. Does anyone else remember A N Beck & Co of (I think) Stoke Newington?
My chemical efforts were boosted by F Sherwood Taylor’s seminal work The young chemist, although I didn’t try to make hydrogen fluoride from old teeth (experiment 81 in the book), probably to the relief of my-long suffering parents.
It would be interesting to see how the chemistry embodied in the sets and the chemicals on offer evolved over the years. When I acquired my first set (ca 1963), the experiments included acids, bases and indicators, hydrogen sulfide and its effects, the crystal garden, preparation of hydrogen, ammonia and hydrogen chloride plus coal carbonisation and double decomposition experiments. I enjoyed the preparative aspects – the creation of new materials from existing ones. The bias in the sets towards inorganic chemistry will be noted; the organic side only arrived with Sherwood Porter. As for an overall description of the genre, ‘educational toys’ would seem to be adequate, rather like Meccano – now there’s another story.
N Jopson CChem MRSC
Milton Keynes, UK
Stories of silicosis
I was fascinated by the mention that silicosis is caused by nascent silica. My late father had the disease, which he contracted in the anthracite mines of the Swansea Valley, which has the highest incidence of silicosis in the UK. I can remember him telling me that the preventative measure was water infusion, which fits with the nascent silica hypothesis.
In his letter, Robert Close states that there is no silica in coal mines, but this is not correct. Apparently it was easier to get compensation for silicosis if one had worked in a silica heading, which would have been dug to get at the coal. Pneumoconiosis was more difficult to obtain compensation for.
I can remember my father telling me that the anthracite was in layers called ‘sleeps’. The silica dust lay between these sleeps and this is what causes silicosis in anthracite miners. Water on its own will not prevent silicosis – a cousin of mine worked up to his waist in water believing that it would prevent the disease, but it killed him in the end.
The Coal Board used to insist that a post mortem was carried out on miners who had been compensated for silicosis. In practice, the pathologist would run a scalpel over the lungs. If this produced a grating sound, there was silicosis.
W Edwards CChem FRSC