I was quite outraged to see the article about the ’golden age of trickery’ surrounding alchemy (Chemistry World, February 2010, p80). David Jones perhaps does not know, or has failed to research, the fundamentals of the sulfur, mercury and salt that are the core of alchemy. He does not appear to know about the medicine of metals, as it is called. In fact, he does not even seem to know about the Emerald Tablet since records, translations, and transcripts of it remain.  

Countless other sources on the issue remain, despite the work of Diocletian. The transmutation of lead into gold is one of the smallest facets of alchemy since it is, primarily, about spiritual purification/transmutation/transcendence. The art of making gold was largely the start of conjuring magic tricks and not the art of alchemy.

L O’Neill 
By email

David Jones replies:

I feel that alchemy was not a spiritual exercise but a very practical one, and that making gold was an important part of it. I have a source saying that Sarah, wife of Abraham, wrote some cryptic instructions for making gold on an Emerald Tablet, which Alexander the Great discovered in a cave near Hebron. If a transcript survives, I’d love to know what it says!

Meanwhile, I continue to regard alchemy as a poor precursor to chemistry. My main sources have been the  scientific historian Alec Campbell, and J R Partington’s  Short History of Chemistry. Partington says that salt, sulfur and mercury were introduced as basic ’principles’ by Paracelcus in about 1520, an aid to his ’iatrochemistry’, which treated the sick with new substances. 

All the aims of alchemy - the transmutation of metals, the healing of the sick, the discovery of the elixir of eternal life and of the universal solvent - failed, and now look chemically absurd. Its one success, the discovery of phosphorus, was a lucky accident. 


Being an engineer over the age of 30, I could not help noticing that the picture of the vernier scale in Classic kit (Chemistry World , March 2010, p68) indicated a reading of 1.01 cm, not 1.02 mm as stated. 

A case of high precision ruined by poor accuracy of reading? 

J Jamieson 
Marlow, UK  

Ed: Several readers have pointed out this error - thanks also to David Whan of Darlington, UK, and Mike Flux of Leyburn, UK, for their contributions. The correct reading of this scale should be 1.01cm or 10.1mm as indicated by the precision rating of 0.1mm. 



Rajendrani Mukhopadhyay writes that documents from ancient Egypt clearly discussed how lead shouldn’t be ingested but only applied to the skin (Chemistry World, February 2010, p34). 

If so, their toxicology was thousands of years ahead of its time. Lead was only removed from the composition of pewter in 1974 by British Standard BS55140, followed by a European Directive in 1994. 

E J Rothery FRSC 
Dublin, Ireland  


Can any of the readers of Chemistry World  please tell me if there is anything unique about Droitwich Spa Brine? 

Newspaper cuttings from the 1930s tell of the brine being used to treat heart conditions and to improve muscle strength.  

One book says that: ’analysis of the Droitwich Brine has shown it as containing in every gallon about 20,000 grains of saline constituents in excess of those possessed by the waters of other European Spas’. 

G Mellor FRSC 
Droitwich Spa, UK  


The feature on dental materials suggests that the decline in the use of dental amalgam is partly due to health concerns over mercury (Chemistry World, February 2010, p48).  

However, amalgam is completely different from mercury. The formation of dental amalgam involves thorough mixing of amalgam capsule (containing mercury liquid and the alloy) in an amalgamator. With this high speed mixing, the γ- phase Ag-Sn species reacts with mercury and thus various species are formed, for example:  γ-1 phase Ag-Hg and γ-2 phase Sn-Hg species. The mercury is a limited reactant and therefore, in the final set product, an amalgam matrix with no free mercury should theoretically be formed.  

Although incomplete mixing may occur and residual mercury may be left, a dentist or dental surgery assistant, by training, should visually determine that the amalgam capsule does not leave any shiny liquid before applying the amalgam to the patient. This can minimise the mercury exposure risk.  

Commercial factors also play a role in the decline in the use of amalgam. Composite filling materials are usually less hard than amalgam. After less than 10 years, the composite filling materials can be distorted and therefore need to be replaced - involving seeing the dentist and spending money again.  

J K-H Tsoi MRSC  
Hong Kong  


Caroline Tolond’s article on moving to Canada was slightly on the optimistic side (Chemistry World, February 2010, p72). It should have included the warning: ’do not arrive in Canada without having a firm job to go to, despite what you have learned from official websites claiming that there is still a severe shortage of skilled workers in Canada.’ 

There are thousands of highly skilled engineers, scientists, architects, economists, doctors etc, driving taxis in all the major cities in this country. The reasons for this are either that they have ’no Canadian experience’, or are ’overqualified and would hate this job’ or simply that the qualification is dismissed as inadequate.  

A few go back home but most stay because, having sold everything to come here, there is nothing to which to return. 

I have several examples from my own students failing to get science jobs. One of my post-docs, from Britain, had not found a job after several years with me, and as an experienced amateur pilot decided to apply for a job as an air-traffic controller; giving my name as a reference he told me only to say that he had been working with me as a lab technician and not to give any hint that he had a PhD. 

When you have a job to come to, get it all down in writing, on letterhead, not over trans-atlantic telephone calls as I did. I thought I had tenure when I came here in 1965, only to find out later that I did not. And get as much information as possible about your pension scheme.  

This ’no Canadian experience’ gig has been going on since before I came here, and is widely practised. It is nothing more than a respectable form of xenophobia, a problem that has not yet been solved. 

H O Pritchard MRSC 
Toronto, Canada  

Caroline Tolond replies:  

Huw Pritchard is absolutely right. Regardless of the country you are considering moving to, if you don’t have written confirmation of a job offer then you may find it very difficult to find an appropriately skilled job and the situation is often more acute for those with specialist qualifications, such
as a PhD. 

Make sure you do your homework about a country before you make any move, be realistic about what you want to achieve, and set a deadline by which to secure an appropriate job if you decide to move without a firm offer.


The recent article on the Perkin family reminds me of an incident in my own career (Chemistry World, March 2010, p54). I was a postgraduate member of Frederick E King’s Nottingham group working on extractives from hardwoods. I had produced a saponin from which aqueous acid hydrolysis produced a white powder which I could not crystallise.  

Sir Robert Robinson came to lecture and toured the research laboratories. I was introduced to him and explained my crystallisation problem. Sir Robert said: ’if Perkin had had that he would have dissolved it in alcohol, saturated the solution with ether, washed out the alcohol with water and left the solution on the bench to crystallise. It is always a good thing to ask ourselves what Perkin would have done.’ 

I tried Perkin’s method and it worked! 

J A Baker FRSC 
Woodbridge, UK