Letters

From Alfred Bader

Why do chemists refer to Avogadro’s number (Chemistry World, August 2007, p11) when, correctly, it should be called Loschmidt’s number? Amedeo Avogadro predicted in 1811 that someone, some day, would be able to calculate that number. The calculation of the number was first done by Joseph Loschmidt in Vienna in 1865. 

A Bader CBE FRSC, Bexhill-on-Sea, 
East Sussex, UK

From John Holman

Peter Cotgreave highlights the importance of specialist qualifications for those who teach chemistry in schools (Chemistry World, August 2007, p38). Many children (half a million on Peter Cotgreave’s figures) are taught chemistry up to the age of 16 by teachers whose first degree is not chemistry. But many of those teachers are very skilled, experienced and inspiring, even though their degree may be in biology or another science. I have met and worked with many such teachers and it would not be fair to describe most of them as ’not really chemistry teachers’. If they teach chemistry well, they are chemistry teachers in my book - I’d rather have a skilled and inspiring teacher with a non-chemistry qualification than a dull one with a chemistry degree. 

That said, when all other things are equal, classes are better off when they are taught by a specialist. OfSTED data shows that when teachers’ qualifications are well matched to the curriculum, pupils’ achievements are better.

We do need more specialist chemistry teachers, and the government’s drive to recruit more, through ’golden hellos’, training bursaries and conversion courses, is aimed at doing that. The aim is for 31 per cent of science teachers to have a chemistry specialism by 2014 - with one third of the science curriculum being chemistry, that’s the proportion needed (the current proportion is 25 per cent). 

J Holman CChem FRSC 
Director, National Science Learning Centre, University of York

From John Thomas

The brief news story ’Poor Pauling’ (Chemistry World, September 2007, p9) reflects poorly on the only sole recipient of two full Nobel prizes (Chemistry in 1954 and Peace in 1962). True, Linus Pauling was adamant in his belief of the powers of vitamin C, and his long life - he died half way into his 94th year - did not seem to have been hindered by enormous doses.  

Certainly, while there is scepticism on the powers of vitamin C, there are many who have considerable faith in its perceived role of reducing the incidence of colds. Also, vitamin C is significant in healthy eating recommendations of five portions of fruit a day. It promotes healing, and many believe in large doses of vitamin C ahead of teeth extraction. 

J D R Thomas CChem CSci FRSC
Gresford, Wales, UK  

From Dana L Roth

I was a little annoyed with the tone of the ’Poor Pauling’ news item. I have been following Pauling’s vitamin regimen for several decades and have never come down with the flu, and a rare cold is of very short duration. Pauling recommended gramme quantities of vitamin C, not the trivial dose of ’at least’ 200mg related to the thirty trials you mention.  

There is recent research (C V Dang, Cancer Cell, 2007,12, 230) indicating that vitamin C can impede the growth of some types of tumours.  

If studies on the value of vitamin C are to be taken seriously, some allowance must be made for diet, life style and the source of the vitamin C. For example, there is also a report (I J Wilk, J. Chem. Educ., 1976,53, 41) showing that ’ascorbic acid in commercial vitamin C products ... degrades fairly rapidly’. This is not true with crystalline or powdered ascorbic acid.  

D L Roth
Pasadena, California

From Robin Wilkinson

Your recent article ’A viable alternative’ (Chemistry World, August 2007, p12) gave a misleading impression about the conclusions of the US National Research Council report on toxicity testing. The report is rightly supportive of recently developed non-animal methods, but it is no less supportive of animal methods where alternatives are not yet available or not yet validated. The report also recognises the contribution that new techniques such as genetic modification are likely to have on animal models, making them more accurate and useful. 

Significant advances have been made, and will continue to be made, in developing non-animal methods. A premature relinquishing of animal methods for unvalidated, and possibly less accurate alternatives, would have serious implications for human health. 

R Wilkinson, Science Communications Officer
RDS: Understanding Animal Research in Medicine, London 

From E R Gleave

Chemistry World  may have solved a mystery for me. It seems zeolites may be to blame for the allergy problem that lays me low after replacing the bedding (Chemistry World, August 2007, p34); and after working in my garage, where the tumble drier sends its exhaust; and after handling large amounts of paper, which presumably disperses its clay content into my airspace. Perhaps someone can solve the consequent mystery for me. Where can I buy zeolite-free (and perfume-free) washing powder with which to test the hypothesis? 

E R Gleave,
by e-mail

From Ed Rooney

I was amused by the article ’Slip slidin away’ (Chemistry World, October 2007, p12). I couldn’t decide whether the word ’tear’, in the phrase ’early petroleum-derived lubricants could plasticise latex, leading to holes and tears’, was referring to the physical ripping of the condom or the emotional outcome on discovering this unwelcome failure.  

E Rooney CSci CChem MRSC
Yateley, UK 

From Mike Sinnott

It was good to see a page devoted to the important issue of paper permanence (Chemistry World, September 2007, p11), but unfortunate that the actual text disseminated some minor historical misconceptions and a major chemical one. 

Papermaking is essentially a high-speed filtration of a slurry of cellulosic fibres through a wire mesh to form a random web, which is then pressed and dried. The industrialisation was unrelated to the increase in the acidity of the papermaking water systems between, say, 1815 and 1850, which was actually a consequence of the introduction of a ’rosin-alum’ surface coating, to avoid wicking when ink is applied. Gelatin had previously been used, which acts as a pH buffer, but the switch to ’papermakers’ alum’ [Al₂(SO₄)₃?xH₂O] required a lower pH to avoid the precipitation of basic aluminium salts. 

Loss of paper strength is associated with a reduction of the degree of polymerisation of the cellulose molecules making up the fibres, and the much worse permanence of paper coated with rosin-alum, compared to gelatine, was assumed to be due to a proton-catalysed hydrolysis.  

Yet our measurements of the rate of hydrolysis of a model compound revealed a different picture. At constant pH, the hydrolysis is strongly accelerated by added Al(iii) salts, which act as efficient electrophiles (J Baty and M L Sinnott, Chem. Commun., 2004, 866). Moreover, it is only at pH ?3.5, below the normal pH range of ’acid’ paper, that acid-catalysed hydrolysis is by itself fast enough to reduce cellulose polymerisation sufficiently to affect mechanical properties in decades rather than centuries (Can. J. Chem., 2005,83, 1516). The problems of rosin-alum sized paper thus arise from Al(iii) acting directly as a Lewis acid, rather than the water molecules in its coordination sphere acting as Br?nsted acids. 

Mass deacidification protocols will have some effect by deprotonating coordinated water around Al(iii), making it a less avid electrophile. However, a more rational approach would be to remove the Al(iii), perhaps using fluoride, or switch to low-temperature storage. 

M Sinnott MRSC
University of Huddersfield, UK

From Alan Hero

The comment article by Bernard Bulkin (Chemistry World, October 2007, p39) appears to suggest that the Lurgi gasification of coal followed by the Fisher-Tropsch synthesis route to syngas is no longer important to South Africa following the ending of apartheid. This is definitely not the case. The process continues and gasifies more than 30 million tonnes of coal per year, producing transport fuels and plastics amongst others. The diesel fuel produced is of very low sulfur content and some of it is exported to Europe.  

The company Sasol has plans to increase the number of gasifiers from the current 80 by another 40, so production of syngas will expand considerably over the next few years. 

The technology may even be installed in the USA to meet their continued shortage of transport fuels and reduce reliance on oil from overseas. 

A A Herod CChem FRSC,
Imperial College London, UK

From Humphrey Yiu

Scientific research can be influenced by trends. In the 1990s, key words for research projects were ’green’, ’environmentally friendly’ and ’high throughput’. Then we had ’supramolecular’, ’miniaturisation’ and ’interface’. And now, it is ’nano’ everywhere. But what is nanotechnology?  

Three years ago, I went to a nanobiotechnology meeting at London and found about half of the presentations have very little to do with real nanotechnology. One of the keynote lectures was on measuring movements of wings of insects at the nanometre scale. Others were just pictures of nanocrystals of some biological samples (we called them ’crystallites’ in the past).  

Then this summer, I went to the IEEE Nanomed conference in Macau, attended by many scientists from North America and Asia. Shockingly, I found that some scientists have started to label anything small as ’nano’. For example, there was a presentation on enzymatic catalysis and enzyme inhibitors - while an enzyme molecule is around a few nanometres wide, are they really ’nano-catalysts’? Or is this actually the molecular biochemistry that we have been learning for decades?  

If we define ’nano’ by scale alone, then most chemists are working on ’nanochemistry’. I wonder if any mathematical expressions involving the magic 10^-9 are classified as ’nano-mathematics’? We need to stop abusing this word ’nano’. 

H H P Yiu CSci CChem MRSC
Stoke-on-Trent, UK 

From K F Langley

In recent issues of Chemistry World  there have been several references to the problem of what to do with plutonium, which has also been the focus of considerable media interest following the publication of a report by the Royal Society into options for dealing with the country’s stockpile of separated plutonium.  

We are told that this material is too dangerous to store indefinitely and should either be used as mixed oxide fuel in pressurised water reactors or buried in a geological repository as waste.  

In my view, this report greatly overestimates the difficulty of storing this material safely and securely, and underestimates its potential value.  

Used in a fast neutron reactor cycle, together with our vast stocks of depleted uranium, the plutonium stockpile could provide all our electricity needs for centuries to come. This is a technology that is proven and is economic at the current prices of fossil fuels and uranium. 

Your October 2007 edition also gives interesting summaries of the development of alternative energy technologies, such as fuel cells, hydrogen production, and electric vehicle storage batteries.  

Although there have been many scientific advances recently, it seems to me that none of these technologies are any nearer to practical deployment than they were when I studied them 25 years ago in the Energy Technology Support Unit (ETSU) at Harwell. 

K F Langley CChem FRSC
Oxford, UK.