Recently a student asked me about how to deal with the problem of making molecular orbitials in a polyatomic molecule. For example we can consider carbonyl sulfide (S=C=O). This has a sulfur, a carbon and an oxygen. The first step of the problem is to count up the number of valence electrons which the atoms have. For it is best to have a periodic table to hand. We should now make a Lewis strucutre for the molecule, we need to decide what the central atom will be in the molecule. I am sure that C=S=O will be a far higher energy than O=C=S and anyway if we look up the strucutre of carbonyl sulf ..read more

Dear Reader, I have been asked to explain the dire event which occurred this week in Beirut, what happened was that thousands of tons of ammonium nitrate stored in a dockside warehouse exploded after a fire broke out. My view of the event is that we are facing the problem of the DDT (deflagration detonation transition). This is an important thing to understand in energetic materials, it is possible for a single substance or composition to react in both a deflagration and a detonation. In a deflagration a reaction front moves through a mass of material by means of heating, as one part of the ma ..read more

Dear Reader, I have become aware that Donald Trump (not the most level headed of men) has thrown a tantrum during a meeting with members of the press. Now I am sure that many of the readers of this blog will have spotted some time ago that Donald is not “of sound mind and sober habit“. By the way I can not claim to have coined this wonderful phrase, it is a phrase from the UK law on firearms and explosives. Section 25 of the 1968 Firearms Act states “It is an offence for a person to sell or transfer any firearm or ammunition to, or to repair, prove or test any firearm or ammunition for, anothe ..read more

Dear Reader, I feel rather shocked at the new virus, now I think we should all sit down and have an adult conversation about risk and reward. When I was a PhD I have the privilege to be a member of the Loughborough and District Amateur Radio Society. One of the men in the club was a high voltage electrical enginner (expert in protection and switchgear) who had spent much of his life building and servicing high voltage systems. He told me a story from his youth about risk and reward. In world war two he was a test pilot, it was his job to fly bombers after their wiring had been modified around ..read more

Dear Reader, I was recently at Nuclear Chemistry when Anders brought a collection of scientific toys along, Anders operates a on line store which sells a range of different things. All of his toys are things which have a strong science theme in them. When I got home, my wife (Paula) looked at what I had and she was of the view that I looked happy with the range of things which I had brought home. One of the items I had got was a visible spectrometer which contains a grating, a slit and a lens. After an hour or so of folding and gluing with UHU solvent glue I was ready to go with my spectromete ..read more

Dear Reader, I enjoy solvent extraction, it is enjoyable and allows me to probe the very fabric of matter with a simple experiment which measures a system at equilibrium. While there are some things which solvent extraction can not do such as prove the existence (or non existence) of God there are lots of things it can do. Now I am aware of a man who has attempted to use quantum mechanics to prove that Christianity is right this is a true story and not a joke, but we will leave that matter for another day and get back to solvent extraction. Now lets consider the things which solvent extraction ..read more

Dear Reader, It has come to my attention that a group of protesters have caused a great deal of disruption in central London. These protesters are concerned about climatic change and air pollution. The problem I see with these people is that they seem so blinkered by their devotion to their cause that they fail to see that they may well be sabotaging their own campaign. Now before we get going, I hold a view that we should exercise care with the environment on earth. To be blunt with you, if we foul it up then we can not go to the shops and buy a replacement one ! But if while campaigning for ..read more

Dear Reader, It has come to my attention that the EU will soon be banning a fungicide named chlorothalonil. This is a rather small molecule which has one benzene ring in it, two nitrile groups and four chlorine atoms. The molecular structure of this substance was reported by D. Britton (Cryst.Struct.Commun. , 1981, 10, 1501). Here is a picture of the molecule. Some of the chemistry and biology of this pesticide is discussed in a paper from the EFSA. This is a paper with a lot of authors. Maria Arena, Domenica Auteri, Stefania Barmaz, Giulia Bellisai, Alba Brancato, Daniela Brocca, Laszlo Bura ..read more