Letters: December 2007

From David Feakins

Congratulations on the splendid October issue of Chemistry World. I found all the articles on the topic of energy absolutely riveting. For example, I have always been a supporter of nuclear fission as a medium-term answer to the supply of energy, but had not realised until I read Richard Van Noorden’s article (p52), how strongly the facts support my prejudices!  

As you say in your interesting editorial, many of the problems in this field are political. So lucid and wide-ranging are the articles that politicians could benefit from reading them. If extra copies are available I would, as a Conservative, be happy to send David Cameron one. Thank you again for such a stimulating read.

D Feakins FRSC
Birmingham, UK

Ed: Glad you enjoyed the issue - the copies are on their way 

From Trevor Mathers

Having read Sense about Science’s publication There Goes the Science Bit  recently, I was glad to see Neil Young giving the exercise in debunking pseudoscientific marketing some publicity in Chemistry World  (November 2007, p43). Unfortunately, two pages previous, J D R Thomas’ letter regarding vitamin C intake employed many of the ploys used in pseudoscientific marketing: 

• Use of celebrity: ’Linus Pauling. did not seem to have been hindered by enormous doses [of vitamin C].’ Two full Nobel prizes does not make him infallible. 
• Using anecdotes as data: ’Many have considerable faith in the perceived role of reducing the incidence of colds’. 
• Build up false arguments out of context: ’vitamin C is significant in healthy eating recommendations’. 
• Distort the facts: ’...healthy eating recommendations of five fruits a day’. The recommendation is five fruit and vegetables a day. 
• Use woolly language which is meaningless: ’...[vitamin C] promotes healing’ 
• Appeal to belief and superstition: ’...many believe in large doses of vitamin C ahead of teeth extraction.’ 

Looking out for these six criteria will cut through most of the ’science’ we get via marketing - even in personal letters! 

T Mathers MRSC 
Chippenham, UK

From Michael Hollas

There may be some doubt as to whether we should refer to Avogadro or Loschmidt (Chemistry World, November 2007, p40) but there is no doubt that we should refer to their constant and not their number. Anyone in the chemistry department at the University of Reading referring to the Avogadro number would have been politely corrected by either Edward Guggenheim or Ian Mills. The Avogadro constant, as it should be called correctly, is a constant rather than a number because it has units (mol^-1). This contrasts with, for example, the Mach number which has no units, being the ratio of two speeds: it is a pure number, unlike the Avogadro constant.  

J M Hollas MRSC
Henley-on-Thames, UK

From Brian Innes

There is a famous French advertising slogan, ’Jamais d’eau sans Pernod’ (’Never water without Pernod’). But the reverse, it appears, is equally true. If any of the many brands of pastis is left standing in daylight undiluted, it develops an unpleasant taste of hay.  

Dario Bassani, a member of the team devoted to organic nanostructures at the Institut des Sciences Moleculaires in Bordeaux, has reported the reason in Vie des Labos  (July-August 07). [The discovery is also reported in  Chemistry World, April 2007, p26]. When a molecule of trans -anethole - which is responsible for the flavour of anise - absorbs a photon of light, it is transformed into cis -anethole, with its unacceptable flavour. 

Researchers have discovered that the rate of transformation is greatly inhibited when the trans -anethole is emulsified into a mixture of alcohol and water, and the true flavour of pastis is preserved for the pleasure of the drinker. 

Bassani explains that, thanks to the emulsion immediately produced with the water, the molecules of trans -anethole come into continuous collision with each other, and this dissipates the energy acquired from the light. 

It might be thought that this spontaneous emulsification is of interest only to French imbibers, but researchers at the Montpelier laboratory of macromolecular chemistry are further investigating this ’pastis effect’. Generally, stable emulsions can be produced only by violent agitation or the use of ultrasound, or the addition of tensioactive products. Spontaneous emulsification could obviously be of great value in industry. 

Pastis manufacturers inhibit the effect of light by enclosing their products in bottles of dark-coloured glass. Strangely, this does not appear to be the case with Greek ouzo - further research is obviously needed! 

B Innes, MRSC
Montgaillard, France

From Huw Pritchard

Sean Milmo (Chemistry World, October 2007, p48) states that ’a tank of bioethanol blend with gasoline emits 2 per cent less in CO₂ emissions than a tank of unblended gasoline’. It is simple to show that for the 10 per cent ethanol blend widely available in Canada, the energy content per litre is about 3 per cent less than for gasoline alone (assuming that there is no volume change on mixing), implying that one needs roughly 3 per cent more fuel to travel the same distance. Thus, there will be no significant difference between the CO₂ emissions by using either fuel. 

H O Pritchard, MRSC, 
Professor Emeritus, York University, Toronto, Canada

From Leif Holmlid

In an article ’Hydrogen storage targets out of reach’ (Chemistry World, October 2007, p14) you state that it is not possible to store hydrogen efficiently. But the form of hydrogen described in our paper (S Badiei and L Holmlid,  Energy & Fuels,2005, 19, 2235 (DOI:10.1021/ef050172n)) has a density of 0.5 to 0.7 kg/dm³, which means that one can have 15 kg of hydrogen in a space of the size of a petrol tank, more than the 5 kg required by the US Department of Energy. 

L Holmlid
G?teborg University, Sweden

From Brian Willacy

With delight, I have read your last two leaders in Chemistry World  and noted the absence of ’chemical scientist’ and ’chemical science’. Our profession and discipline, chemist and chemistry, the correct nouns, are used throughout. My hope is that practice will spread to all RSC publications. 

With respect to methyl iodide in crop protection, in addition to its methylating nature, about 7 per cent of mankind is iodine allergic. Whilst residual amounts in food are unlikely to be a problem for consumers, workers applying the treatment may well be at risk and, in extremis, fatally so.  

B M Willacy CChem
Chesterfield, UK

From Philip Miller

Call me image conscious (excuse the pun) but I couldn’t help but notice the image discrepancy in the article ’MRI scanners get EU reprieve in legal U-turn’ (Chemistry World,  November 2007, p9). The article discusses the implementation of EU directives on some of the safety issues of high-field MRI scanners, but the picture is clearly referring to the distinctly different molecular imaging technique of Positron Emission Tomography (PET). The offending picture shows a collage of PET images of the brain, decay processes, a detector ring and some of the common short-lived radionuclides (¹¹ C, ¹⁸ F, ¹³ N and ¹⁵ O) used in PET. Chemistry World  should perhaps (again, please excuse the pun) ’get its image right’ when it comes to molecular imaging techniques and run a feature issue on this important and rapidly expanding area of science. 

P Miller MRSC
Imperial College London, UK