From Barry Knight

Richard Biddulph asks whether there is a procedure for neutralising acid inks using zinc diethyl (Chemistry World, November 2005, p32). The Library of Congress, Washington DC, US, did indeed carry out lengthy experiments on deacidifying books with diethyl zinc (DEZ) in the 1980s. However, DEZ reacts violently with oxygen, water and acids, and it proved very difficult to control the process. The results were not very satisfactory, and ultimately the process was not cost effective.  

The Library of Congress now uses a much more benign deacidification process in which books are immersed in a fluorocarbon solvent containing dispersed microfine particles of magnesium oxide. These particles neutralise acid present in the paper, and sufficient is deposited on the surface to give an alkaline reserve to neutralise acid that will be produced in future by the slow oxidation of the paper.  

The British Library does not currently have a programme of mass deacidification, but it is a partner in the EU-funded PaperTreat project, led by Jana Kolar of the National and University Library of Slovenia, which aims to assess the long-term effectiveness of existing commercial mass deacidification processes.   

B Knight CChem MRSC
Head of conservation research
The British Library  


From Michael Baldwin

In answer to Norman Nicholson’s query about gunpowder, (Chemistry World, December 2005, p27), the sulfur in gunpowder is converted to potassium sulfate, potassium thiosulfate, hydrogen sulfide and potassium sulfide. An approximate representation of the combustion is: 

14 KNO3 + 4S +12C = 3K2 CO3 + 8CO2 + CO +14N

Sodium nitrate was used in special grades of gunpowder, called N/P and N/S powders. They were deliquescent, but rather more powerful than the potassium-based powder. They were used to blast the Suez canal. 

In the UK, potassium nitrate was originally made by a lixivation process involving nitrogenous waste, wood ash (potassium carbonate) and lime - which precipitated sulfate and carbonate. 

The availability of natural Bengal saltpetre, an impure form of potassium nitrate, reduced the importance of this process. Chile saltpetre, or sodium nitrate, was converted into the potassium salt by double decomposition with potassium chloride, which depended on the very steep temperature/ solubility curve of potassium nitrate. 

This process was conducted by Nobel’s Explosives Co at its factory in Gatebeck, Cumbria, UK. The product was of good commercial quality but was not pure enough to manufacture sporting powder or military shell fuses. 

M Baldwin CChem FRSC
Sittingbourne, UK


From Andrew Williams

Potassium sulfide is the main sulfur product in exploded gunpowder. 

4KNO3 + 2S + 6C = 2K2 S + 2N2 + 6CO2  

Sodium nitrate is a main source of saltpetre. The process depends on the relative solubilities of KNO3, NaCl, NaNO3 and KCl. Strong hot aqueous solutions of KCl and sodium nitrate deposit the relatively insoluble NaCl which is filtered. On cooling, the potassium nitrate becomes the least soluble component and is isolated by filtration.  

A well-known thermodynamic principle is also involved in this process: 

Hot (100?C)  

NaNO3 + KCl = KNO3 + NaCl ?   

Cold (0 - 10?C) 

NaNO3 + KCl = KNO3  ? + NaCl 

A Williams
University of Kent, UK


From Frank McGurty    

I was wondering if anybody could find a home for a fine Oertling analytical balance that I have rescued from being sent to the rubbish tip. It is housed in a polished wooden and glass case and is in good condition although the glass in the top cover is cracked. It has a 30g capacity but I’m not sure if it’s a four or five figure balance.     

I rescued it because I thought it may make an interesting conversation piece but it takes up too much room and is out of place in my small house. It might be of use to a school or a museum or it may form part of an enthusiast’s collection.   

If anybody would like it they are welcome to have it free of charge provided they can arrange for its collection.   

F McGurty CChem MRSC  
Cockermouth, UK   


From Jack Barrett

Richard Brown states that parts per million by volume (ppmv) are not part of the SI system of units (Chemistry World, December 2005, p27). However, they are used by the Intergovernmental panel on climate change and climatologists to indicate the concentrations of gases in the atmosphere. 

Richard Brown states that parts per million by volume (ppmv) are not part of the SI system of units (Chemistry World, December 2005, p27). However, they are used by the Intergovernmental panel on climate change and climatologists to indicate the concentrations of gases in the atmosphere. 

J Barrett CChem MRSC
Kingston upon Thames, UK 


From John Leisten

The discovery that group 8 gases can form some compounds was exciting to chemists who had been taught to think this improbable but to later generations it may seem unremarkable.  

On the other hand, the inertness of these elements, compared with the reactivity of their neighbours in the periodic table, provides some of the most dramatic contrasts in the whole of chemistry. They will never fail to help chemistry teachers and spark students’ interest. 

Low reactivity is the obvious characteristic of the whole group. Can inert not be used in a relative sense? Am I alone in thinking that the name of the inert gases should never have been changed? 

J Leisten CChem FRSC
Queensland, Australia


From Roger Brettle

The feature entitled Explosive science has an incorrect formula for triacetonetriperoxide (TATP) (Chemistry World, December 2005, p51).  

I imagine that any molecule containing tetravalent oxygen might be highly explosive but perhaps this is a way of putting off potential makers of homemade explosives by printing the wrong formula! 

R Brettle CChem FRSC
By email

Chemistry World responds:

While we would like to claim that the error in the TATP structure was deliberate, this is not the case.  


From Trevor Kletz

I recently spotted an error in a chemistry newsletter where carbon dioxide was described as inflammable. This word does not mean non-flammable, but able to catch fire or inflame. Compare it with the word inspire which means to breathe spirit into someone. 

Before the Health and Safety at Work act came into force in the UK in 1974, storage tanks containing petrol or other light hydrocarbons had to be marked inflammable although the Factory Inspectorate required tanks containing other highly flammable liquids to be marked flammable. The UK Health and Safety Executive, established in 1974, required both groups of tanks to be marked flammable. 

Insisting on the correct use of inflammable may seem pedantic but unless we do so, in a century’s time historians will be showing pictures of petrol tanks to prove that in the 20th century legislators did not realise that petrol could burn.   

Another word of uncertain meaning is, or was, billion. Before 1960 in the UK it meant a million millions. Since 1980 it has meant a thousand millions, as in the US. In documents written between these two dates we have to guess the meaning from the context. I recall that at a meeting in 1968, when someone referred to a billion I asked him what he meant and it was sufficient for him to reply: ’I am an Englishman’.   

T Kletz CChem FRSC
Cheadle Hulme, UK


From Anthony Davis

I find it deeply worrying that, since the 1986 explosion at Chernobyl, I have seen no statement that other existing nuclear reactors lacking a containment vessel are to be taken out of service.  

Even if the causes were different, the accidents at Chernobyl and at Three Mile Island, US, in 1979, both involved a core meltdown. The fact that radioactive pollutant release was minimal at Three Mile Island and disastrous at Chernobyl was entirely due to the presence of an effective containment vessel at Three Mile Island and its absence at Chernobyl.  

It is unfortunate that this point was not hammered home in the press at the time. We need to be sure that new reactors to be planned and constructed in the UK do not invite such frightful consequences in the event of accident by omitting the containment vessel. I feel that we should also be campaigning to have reactors lacking a containment vessel outlawed in all countries. 

It is unfortunate that current favoured reactor designs mostly involve the presence of water in the reactor core. However great the claims made for such designs, they all carry the risk of a disastrous pressure rise in the event of overheating, because of the phase change from water to steam.  

Only a gas-cooled reactor is free from such objections. This point also deserves wide public debate. 

A C Davis MRSC
Harrogate, UK