Saturday, 22 November 2014


Peter Greiß was a mid-19th century organic chemist from Germany who left for England to work with Hofmann at the (UK) Royal College of Chemistry.  He married an Engländerin, chamnged his name to Griess, refused a good offer to return to the fatherland with a position BASF and worked for the Allsopp's brewery until he died. He's buried in Burton-on-Trent, England's brewing Mecca. BASF BLOB BOOM.  His lifetime's work with nitrites, diazonium salts and other nitrogen rich organic compounds made it inevitable that he would contribute to our understanding of nitroglycerine and TNT trinitrotoluene. Those years were exciting for chemists and in the course of that century science went from knowing very little to knowing a lot about how chemicals interact and how we can tilt reaction processes to favour desirable outcomes.

The Griess test for the presence of nitrates and nitrites is named for him because he invented it in 1858. The previous paragraph and a previous Blob shows that nitro-containing compounds lean towards flammability, not to say explosiveness, because of the excess oxygens that are embedded in the molecule and so don't need to be found from the surrounding air when things blow up.  If you use caustic soda - NaOH - you can strip off the nitro parts of unexploded TNT or nitroglycerine (the active part of dynamite) and then carry out the following two reactions.  First add sulphonamide to make a diazonium salt with a rather reactive N=N side-chain.
If you then add N-alpha-naphthyl-ethylenediamine and it turns pink, then you must have had some nitro groups in the original sample . . . and those nitro groups must have come from an explosive material.
All this stuff about nitroglycerine and the Griess test is because sometime in the small hours of 22 November 1974, a government appointed forensic scientist was swabbing the hands and fingernails of six Irishmen who had just been arrested in the port of Heysham.  The police were certain-sure that they had nabbed the fleeing perpetrators of the Birmingham pub bombings which had ripped through some scores of people the night before and killed 21 of them. While the boffin was taking the swabs and analysing them to produce one plank of the evidence, the police were extracting confessions from the arrested men. One problem with the Griess test is one of false positives: nitroglycerine will give a pink colour but so will a raft of other common-or-garden substances including detergents used to wash the vials for carrying out the test and lots of stuff (shoe-polish, cleaners) you probably have under your kitchen sink. The analysis hinges critically on the strength of the NaOH used at the very beginning of the test: too weak and it cannot possibly strip off nitro groups; too strong and it will find them everywhere - there is no middle ground, and the Griess test is only useful as an preliminary indicator rather then evidence in itself.

At the trial the following year the judge summed up the evidence thus ". . . if Dr Black [the defense counsel] is right, the Griess test was not worth carrying out... Do you think that Dr Skuse [the govt forensic scientist] has been wasting most of his professional time? It is a matter entirely for you".  As is enshrined in the justice system in these islands, the judge will have made up his mind at this stage in the trial and can phrase his summing up in such a way as to tilt the opinion of the jurors so that - surprise! - they come to agree with the judge.  At the appeal years later the judges had this to say "if the trial judge had known what we know, he would have excluded Dr Skuse's evidence as valueless".  I'm not going to beat up on Dr Skuse here, having had a go at him five months ago, but before you make up your mind you could, with advantage read Beverley Schurr's long essay summarising and dissecting the whole sorry story.  Of course, it's not the whole story, but it's more comprehensive and balanced than the original convictions.

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