Letters: November 2015

Explosive new data

Reading the news that the US National Institute of Standards and Technology’s (NIST) campus in Maryland had a secret meth lab  reminded me of physical chemistry labs. I regularly used the NIST Chemistry WebBook to look up thermochemical data such as the enthalpy of combustion. Looking up methamphetamine on the WebBook strangely doesn’t yield much combustion data. Perhaps they have more data since the explosion? After all, they were in the old combustion research labs.

Matthew Bird
University of Nottingham, UK

Colour-changing antiques

Andrea Sella’s delightful article on Auer’s lamp  touches on two of my interests. It has long been a party trick of mine to demonstrate the radioactivity of Aladdin oil lamp mantles using a Geiger counter while people sit at table. Of greater interest is glass that contains neodymium, usually with praseodymium and sometimes other metals. 

Neodymium has a strong absorption band in the orange part of the spectrum, and the absorption wavelength doesn’t correspond to any emission wavelengths in fluorescent light sources. As a consequence, objects made with this glass, invented by Leo Moser in 1927 and named Alexandrite, change colour when viewed in natural, filament or fluorescent light. Straight neodymium glass is lavender in natural light but green or grey in fluorescent light. Different colour changes occur when other coloured metallic ions are present. 

I always carry a direct vision spectroscope at antiques fairs to detect sharp lanthanide absorption bands in glass. Building a collection is slow work but extremely rewarding, especially knowing that dealers are usually unaware of the treasures they are selling at bargain prices.

Michael K Baldwin CChem FRSC
Sittingbourne, UK

Zeolite minerals

The article ‘MOFs with a heart of glass’, comments on MOFs’ structural resemblance to the ‘aluminosilicate mineral zeolite’. The word zeolite describes a class of natural and synthetic minerals that has hundreds of members. 

Furthermore, regarding the article on the decommissioning of the Sellafield nuclear site, the mode of action of the natural zeolite clinoptilolite at the Sellafield ion exchange plant is not one in which the radioisotopes exchange with ‘silicon and aluminium repeating units’, which are of course anionic, but ion-exchange of cations held within the channels and cavities of the zeolite microporous framework.

Alan Dyer, CChem FRSC

Hoddlesden, UK

Response from Editor: Thanks for picking us up on these errors. We apologise, and hope you enjoy the feature on zeolite catalysts.

Caught wrong-handed

I was appalled to find an article on oligonucleotide drugs was illustrated with left-handed dsDNA twice. DNA is a chiral molecule; it has handedness. The public generally is unaware of this, and it seems that it is more often than not depicted in the (wrong) left-handed form. As a publication of the Royal Society of Chemistry I would expect Chemistry World to know better. From chemists this is not forgivable.

David M J Lilley FRSC FRSE FRS
University of Dundee, UK

Cholesterol danger exaggerated

In response to Andrew Turley’s report of several new statin drugs under development to lower cholesterol, I would like to mention a critical aspect that seems to have been forgotten by the medical and scientific world. Statins mislead people about the dangers of cholesterol. Cholesterol is essential for the health and functioning of all eukaryotic mammalian cells, specifically the cell plasma membranes. It regulates membranes fluidity, preventing membrane structure deformations, regulates the movement of other membrane lipids and prevents lipid crystallisation.

High blood serum levels of cholesterol can cause heart attacks and death in about one in 400–500 people aged 40 years or over in Europe and North America; other surveys suggest around one in 200 people are affected. About one in 1 million people under 20 years suffer heart attacks. Cholesterol is not to blame, but the number of cell receptors that bind to low density lipoproteins.

Cholesterol is needed to repair damaged tissue and muscle and cholesterol needs to be eaten as well as synthesised in the body for recovery from exercise to occur. Therefore people who do proper exercise in general do not need to worry about cholesterol.

The reported dangers of cholesterol are exaggerated and misleading and are not based on biochemical evidence and frequency of occurrence. 

Francis Hooton 
Edinburgh, UK