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More on organic peroxides

Dear Reader,

Regarding the organic peroxides at the Arkema site in Texas, I took the time and looked up the safety datasheet (SDS) of one of their products. I choose an organic peroxide product (Luperox 331M80) which a 80 % solution of a peroxide which is suitable for plastics processing.

Now after the tales of explosion in the popular media I checked the SDS for any signs of explosive behaviour, I did not see any warnings about detonation of the 1,1-di-(tert-butylperoxy) cyclohexane which is the peroxide in this product.

I also note that the product is a very long way away from being an oxygen balanced explosive. If we consider the chemistry of a detonation. It is normally assumed that an explosive such as TNT is converted to a mass of atoms, these atoms then combine to form a series of products.

The formula of the C14H28O4 if we decompose this into atoms then we would have a great deal of carbon and hydrogen which requires an oxidant to burn. If we apply the Kistiakowsky–Wilson rules then we would expect 4CO + 14H2 + 10C as the products. I suspect that the reaction would form a lot of soot and maybe some hydrocarbons. To me this does not look like a compound which has much promise as an explosive.

The formula weight of the compound is 260.374 grams per mole, I have worked out the oxygen balance of it to be -234 %, this is very far away from the values for typical explosives such as ammonium nitrate (+20 %) TNT (-74 %), nitroglycerine (+3 %) and TATB (-56 %). I suspect that such an extreme lack of oxygen together with a lack of nitrogen would lower the heat of explosion to the point at which detonation would be impossible to at least very difficult.

What the substance could do would be to generate heat in an exothermic reaction and thus burst open a container. If we consider a substance which can decompose in a reaction which has an activation energy EA. Then the rate of reaction will be given by the equation (Arrhenius).

k = A exp (- EA/RT)

Thus as A, R and Estay the same, when T changes the rate constant will change.

If we take data from Sigma-Aldrich for the rate of decompstion of di-tert-butyl peroxide and we calculate that Eis 141124 joules per mole. While A is 5.623 x 1013 s-1.

If we consider the energy release when one mole of di-tert-butyl peroxide decomposes to 2,5-dimethyl-2,5-hexanediol then by using the difference in the heats of combustion we can work out the heat (enthalpy) of the reaction. I have worked out that the energy release when one mole of the peroxide decomposes will be 30080 joules.

If the heat capacity of both compounds is assumed to be 310 J mol-1K-1 we can work out what will happen if a infinite drum of di-tert-butyl peroxide is left at 60 oC. The drum would sit nicely doing very little for days on end, and then suddenly it will bite back in a rather nasty way. The temperature will suddenly spike. What happens is that the self heating in the drum will suddenly make it heat up to the point at which it will boil violently.

selfheating of ditertbutyl peroxide

What I did was to compute the rate of the reaction at 60 degrees C, from this I worked out the heat generated by the mixture. I also worked out the amount of the peroxide which had been consumed. I assumed that the reaction rate would be constant for 30 seconds. I worked out the temperature and the peroxide concentration at the end of each 30 second time period and then used these values to start another calculation. After doing this many times I had the data for the graph.

If doubt if I have got the exactly right time between leaving the drum and the fiery exotherm, an error in the activation energy or another parameter will change the answer. What will be needed would be for someone to go and do DSC on the peroxide. compound. It is also important to note that sometimes an impurity can increase the rate of the decomposition. For example amines can increase the rate at which some peroxides decompose.

In a DSC machine a sample is heated in a small furnace in which the amount of heat energy required to increase the temperature of sample. The sample is compared with a blank (empty sample holder). In this way it is possible with a very small sample to determine if self heating can occur.


This should have been in Camera

Dear Reader,

The recklessness of some people drives me to a new level of distraction, I have chosen to not name the case or the newspaper in this blog article but I will tell you the story. Some irksome pest tries to build a homemade bomb, this homemade special fails. Then the news paper reports the court case explaining how and why it failed to detonate.

What I think is that any public discussion of a failed bomb is an educational moment which we are better off without. The problem I see is that building any complex gadget is hard when you have to make everything yourself. Having had an interest in electronics I can tell you that many gadgets have taken a lot of development work to get to the level which the public now considers “normal”.

Also having been in the business of developing chemical processes, I can tell you that the creation of a process (or even just the implementation of an existing process)  can take a lot of work. One of the things which always makes it more easy is a knowledge of how someone else did it successfully and an understanding of what went wrong the last time.

The knowledge that a particular method or material is unsuitable for a task is a great help, it saves a lot of time and effort. The reason is that a person will not go chasing after something which does not work. By publishing a truthful discussion of how a bomber failed the newspapers are helping the next generation of bombers by improving their knowledge.

Some years ago I was told something interesting at the ITU in Germany, they commented that a large fraction of illicit plutonium samples which have been intercepted contain red materials. They believe that the Soviet intelligence services leaked some misinformation about “red mercury”. The story is that “red mercury” greatly increases the ease of building a working nuclear weapon.

By releasing this crazy story about a spoof material, the Soviets were attempting to  waste the time and efforts of would-be nuclear terrorists. By encouraging them to chase a false lead it would have helped world peace. The reason is that every hour and dollar a terrorist spends looking for ways to obtain and use this material is a hour or dollar which they could not use one something which is more likely to provide them with a weapon. Very clever I think !

I have to ask why the facts of this type of case be discussed in public, and why the newspaper staff did not have the sense not to self censor what they published.

Urea nitrate

Dear Reader,

It has come to my attention that a man and his wife have recently been in court accused of the heinous crime of preparing a terrorist bombing. The explosive in this case is urea nitrate which is formed by the protonation of urea by nitric acid. As I have not heard of this substance before I looked its crystal strucutre. Yu.V.Nelyubina, K.A.Lyssenko, D.G.Golovanov and M.Yu.Antipin published a study of this compound which was published in CrystEngComm 2007, volume 9, page 991. The unit cell looks like this, you might think it does not look very interesting.

Unit cell of urea nitrate

Unit cell of urea nitrate

To get a true idea of what the solid looks like you need to grow this fragment and then trim off some atoms, then you will be able to see the hydrogen bonded layers.

Hydrogen bonded layer in urea nitrate

Hydrogen bonded layer in urea nitrate

When you look at the a different urea salt where the anion is hexafluorosilicate, you can see a different type of layer in the solid. Here the number of possible hydrogen bonds are smaller as there is a much lower charge to radius ratio of the anion. The anion is less coordinating. The layers here again like a chess board. Here is a picture of part of a layer.

Ball and stick version of urea hexafluorosilicate

Ball and stick version of urea hexafluorosilicate


Spacefilling version of urea hexafluorosilicate

The basic unit in this solid is a protonated urea which is hydrogen bonding to the hexafluorosilicate anion. Here it is in all its glory.

Hydrogen bonding between the protonated urea and the hexafluorosilicate

Hydrogen bonding between the protonated urea and the hexafluorosilicate


The assault pressure cooker

Dear Reader,

Recently it has come to my attention that a state senator (Stacey Campfield) in Tennessee has been poking fun at the gun control lobby with a picture of a kitchen autoclave with comments about the assault pressure cooker features which it has. I have never considered the tactical pistol grip on a pressure cooker but the forward carry handle makes it much more easy to move a large saucepan around.

While the NRA and the gun lobby are correct when they say that “guns do not kill people, people kill people”, and some of the antigun lobby are trying to use emotive pictures of evil looking guns to scare people into agreeing with them. I think that the likes of Stacey Campfield have missed a clear and important issue.

Now I want to tell you about a weapon which is cheap, easy to obtain and does not jam. It can be purchased from a good hardware shop without raising any attention, there is a zero second wait on this one, no background check. Soviet made examples of this weapon can be obtained in eastern Europe if you know the right person to ask, I doubt if one of these menacing looking soviet made ones will cost more than about 10 or 20 US$. I am sure that those who like the all American example can get one made in the USA, my one is a Chinese made model in a shocking red and black colour scheme.

It is a pickaxe, I am aware that Karla Faye Tucker in Texas used one to commit a murder. Now before the pro gun lobby get excited or the gun-control lobby suddenly want background checks for garden tools like forks, spades and pickaxes, we need to get something clear.

The pickaxe is a garden tool which is very useful for digging. It has many uses which are unrelated to its use as a means of committing murder. When society decides if we should ban an item we need to consider both the legitimate uses of an item and its misuse potential. I hold the view that for both pressure cookers and pickaxes that the legitimate lawful non violent uses of these items outweigh the threat to society posed by the misuse of these items. Thus we should all oppose a ban on garden forks, pickaxes and entrenching tools (foldable spades).

On the other hand we should regulate where and when we can wander with these items, UK law regulates the carrying of “articles made for causing injury to the person” (Swords etc), “articles adapted for use for causing injury” (D cells in a rugby sock or a toilet brush sharpened into a point) and normal tools and household objects being carried around for the purposes of violence such as a kitchen knife, hammer or axe hidden inside a coat of a person of a person going into a nightclub “articles intended for use for causing injury to the person“. While it is perfectly lawful and reasonable to keep a pickaxe in the basement, garden shed or in your hand while you are digging in the garden it is not reasonable to sneak around at 3 AM in dark alleys with it or to try to carry it into an ice hockey or football stadium.

While I hope that reasonable minded people will see that the pickaxe and autoclave should not be banned as they are useful tools which overall make a positive contribution to society, we should consider for a moment a new “garden tool” which is not so easy to justify. This is the TEC-9 digging device, the idea of this tool is that it flings metallic mini spades at the ground which break up the earth to make it more easy to dig. For harder surfaces such as concrete walls alternative steel cored minispades could be used, for very thick steel perhaps a depleted uranium minispade could be used together with an adapted tool.

For those of you who do not know the TEC-9 is a nasty example of a pistol, it is a very short barreled 9 mm handgun which will make it less accurate than a traditional pistol where the magazine goes into the handle so it is likely to be worthless for police use or for target pistol sportsmen. This “digging tool” has clear misuse potential and I doubt if many people (even experienced pistol users) would have the skill required to use it to dig holes in the garden. I also worry about the pollution of the garden with lead and copper, I tend to use carbon steel spades, forks and other digging tools. Also this pistol (digging tool) will create an almighty racket which will disturb the whole town while the alternative technology (garden spade) is cheaper, more easy to use and close to silent.

I hope that it is clear to my readers that overall the TEC-9 digging machine (pistol) will have a negative effect on society. We need to be careful to avoid being seduced by the argument that a object has a lawful use when it has a unlawful use which can harm society. In short we need to avoid allowing people to relabel items to try to evade or bypass laws. Sometimes the evasion through relabeling will increase the threat to society.

I have heard of a case of a man who went into a gay bookshop (I am not saying where or who) and asked for amyl nitrite, the people in the shop were rather aghast and told him that they were not allowed by law to sell him this drug of abuse. He was then told to go over the road to the hardware shop and ask for leather cleaner, he went there and asked for leather cleaner. The shop keeper asked him if he really wanted video head cleaner, he then legally bought a bottle of amyl nitrite which was sold as a household product (rather than as a drug).

Now I hold the view that amyl nitrite is a nasty drug, but it is a drug which has some lawful purposes. It has been used for the treatment of some heart conditions and it has been used as an antidote for cyanide. If those who want to sell it as a recreational drug are allowed to relabel it as a household product then it is likely that the general public (those who do not want to sniff “poppers”) are likely to be exposed to this harmful substance. I have nightmare visions of some person on their hands and knees cleaning the insides of their video machine with their heart pounding like a speared crocodile. These were the words of one chemist I know who was once exposed to amyl nitrite.

The stupid thing about this law was that it was a crime to supply the substance for use as a drug of abuse but it was not a crime to supply it for household use. I think that the law should either have not banned it for recreational drug use or it should have banned the sale of the substance to the general public. To my mind the law was a total ass, as much as a law banning the sale of gin to under 18s but permits the sale of ethanol loaded with juniper extracts to school children as a pencil case cleaning agent bearing the warning “Do not mix with Indian tonic water before drinking the resulting mixture”. For those of you for whom the penny has not dropped I have just made a reference to “Gin and Tonic” being drunk by school children.

We also need to avoid some silly hysterics, one student once said to me that a class of drugs should be illegal in Sweden because they can be used to cheat at sport. This is a silly argument for banning a substance from the general public as a whole. For example maybe I could cheat at sports by fixing car suspension springs to my shoes (maybe I could jump higher like Zebedee {from the magic roundabout} do not try this at home you are likely to come to some serious harm !). We could ban car springs to prevent the abomination and horror of bouncing Mark with his spring shoes but this would deeply harm the interests of Sweden. Imagine having cars with no suspension ! We should not ban something just because someone (with a vested interest) holds the view that this substance or thing has a potential (or well known) misuse.

What society needs when it considers bans for guns, chemicals and pressure cookers is reasonable and rational thought rather than a knee jerk reaction from either the “ban it lobby” or the “anything goes lobby”. We need to weigh up the harm which a ban (or lack of ban) will cause and compare it to the positive effects the things might have on society, only then can we make a sensible choice as what to ban and what not to ban.

Deeply wrong court case

Dear Reader,

It has come to my attention that a British court has ruled that British man is to be sent to the USA for doing something which was not a crime under UK law while he was in the UK ! What the man did was to publish a list of sites where a person can watch pirated films.

Now to be frank with you I think that the US authority have no valid case for asking for the man, if the man is sent to the USA then I should get rid of the wine and cider in my house just in case an arab country like Saudi Arabia asks for me for having broken their law (but neither Swedish or British) by having alcohol in my house.

Also most of the members of the NRA (National Rifle Association) along with Micheal Francis Moore need to be sent to the UK for trial and punishment for having guns without a UK FAC (Fire Arms Certificate), the film “Bowling for Columbine” clearly shows Mr Moore getting a gun from a man at a bank, I strongly suspect that he lacks the FAC needed to legally have the gun in the UK. He did show his film in the UK so if we apply the reasoning of the courts regarding the first case then the 1968 firearms act in the UK should be used on him.

Now before we get going I would like to point out that I think that people should respect copyright and not try to steal the bread from another by stealing copyright. But there comes a point where the cure is worse than the disease.

I would like to point out that in the USA people have freedom of speech which protects the following

A book which teaches you how to make a silencer for a gun (published by George Hayduke, Paladin Press in Boulder [Colorado]), now I hate to have to tell you but I think that a book which praises firearms criminals who vandalise things with guns or mow down harmless birds and teaches you how to make near silent guns is a greater threat to the general public than a thousand lists of illegal movies.

The americans have also allowed the publication of “The Poor Man’s James Bond”, “The Anarchist Cookbook”, “Screw Unto Others: Revenge Tactics For All Occasions”, “High-Tech Harassment How To Get Even With Anybody, Anytime”, “Advanced Techniques of Clandestine Psychedelic & Amphetamine Manufacture”  and a series of other joyous books which I am so sure that sensible people would rather their children are not reading. If you do not guess why each book has clear misuse potential then I suggest you google the title.

I reason that if we allow the publication of this library of amoral or immoral books then we should allow people to publish lists of illegal film and file sites.

The chemistry of fireworks

Dear Reader,

It is this time of year again and we need to think about chemistry for the first years again. Now before I get going I need to give you all a newsflash…..

Chemistry is fun !

One topic which I know that you have been doing is stoichiometry, a bit of a long word ! It is associated with the ratio of different things, a favourite of mine is the stochiometry of explosives, fuels and fireworks. Now what with the disgusting deeds in Norway this year I do not want to discuss explosives with you and frankly I think you might find a discussion of the chemistry of a candle a little dull so I have chosen to do fireworks.

My trusty copy of Michael. S. Russell’s book (The Chemistry of Fireworks) reveals that a range of mixtures of potassium nitrate, sulphur and charcoal (porous carbon) are used to make gun powders. A typical firework uses gunpowder in it for a range of purposes.

The book explains how the typical gunpowder operates by the following reaction

4KNO3 + 7C + S → 3CO2 + 3CO + 2N2 + K2CO3 + K2S

What we need to move forwards is a little thermodynamic data, I hold the view that thermodynamics is a misnomer it should be thermostatics as thermodynamics deals mostly with things which have reached a stationary (equilibrium) state.

Using the heats of formation of the reagents and the products we can estimate the heat of the reaction.

KNO3         DHf = – 494 kJ mol-1

C               DHf = 0.0 kJ mol-1

S                DHf = 0.0 kJ mol-1

CO2            DHf = – 393.8 kJ mol-1

CO              DHf = – 110.6 kJ mol-1

N2               DHf =   0.0 kJ mol-1

K2CO3        DHf = -1151 kJ mol-1

K2S             DHf = -1000 kJ mol-1

We can use these values to estimate the amount of heat released with gunpowder burns

For the reaction

4KNO3 + 7C + S → 3CO2 + 3CO + 2N2 + K2CO3 + K2S

The amount of heat given out is -1688.2 kJ mol-1, as the mass of the bits on the left hand side is 520.077 grams per mole we can make an estimate of how much energy is released when a kilo of gunpowder burns. Which is 3246 kJ. This compares with 4476 kJ for a kilo of TNT.

For those of you who are interested TNT detonates by the equation

2 C7H5N3O6 → 3N2 + 12 CO + 2 C + 5H2

As one kilo of gunpowder will release 15.38 moles of gas while a kilo of TNT will release 44 moles of gas. As the power of an explosive is given by the product of the energy released in the detonation and the volume of gas. Then it is clear that gun powder is about four times weaker an explosive than TNT.

Back to stoichiometry, if we change the mixture used to make gunpowder then the energy yield will change. Before we get going we need to work out some rules.

  1. The reagents are converted into atoms firstly
  2. The first compound to form is potassium sulphide
  3. The second compound to form is potassium carbonate
  4. Then carbon atoms are combined with oxygen atoms to form carbon monoxide
  5. The last oxygen atoms are used to convert carbon monoxide to carbon dioxide

Using these simple rules and the heats of formation I have been able to create a graph of the heat given out per kilo of gunpowder for a range of different amounts of potassium nitrate, I have fixed the number of moles of carbon and sulphur at seven and one respectively. You should be able to see that the heat given out per kilo is highest when 5.21 equivilents of potassium nitrate is used. This peak in the energy per kilo is close to the classic mixture of gunpowder.

Energy per kilo of gunpowder

For an explosive we normally need both heat and gas production, in the following graph I have shown the volume of gas generated per kilo of the powder. We can see that this decreases as more and more of the mixture is made of potassium nitrate.

Volume of gas per kilo of gunpowder

The explosive power of an explosive is given by the product of the gas volume and the heat of reaction, we can see here in this graph that the peak is at 2.92 equiv of potassium nitrate. I think that this calculation is a little misleading as the heat of reaction is so low for a mixture with so little potassium nitrate.

Explosive power of gunpowder

I suspect that the lack of potassium nitrate will slow down the reaction or maybe make it snuff out, so the normal ratio of four moles of potassium nitrate to seven of charcoal and one of sulphur is a good compromise.

It is interesting that a 85 % (w/w) potassium nitrate and 15 % charcoal mixture has been used as a fire extinguishing mixture. Lets do the maths for this mixture and consider the ratios.

If one kilo contains 850 grams of potassium nitrate (KNO3), then this kilo will contain 8.416 moles of potassium nitrate. If all the oxygen atoms in this potassium nitrate are liberated then we will have 25.25 moles of oxygen atoms.

150 grams of carbon is 12.489 moles of carbon.

If we assume that all the potassium atoms are converted into potassium carbonate then we will form 4.208 moles of potassium carbonate.

We will have 8.28 moles of carbon atoms left and 12.624 moles of oxygen atoms left.

If the oxygen atoms react with the carbon atoms to form carbon monoxide then we will form 8.28 moles of carbon monoxide which leaves behind 4.34 moles of oxygen atoms. The oxygen atoms react further to form 4.34 moles of carbon dioxide leaving behind 3.94 moles of carbon monoxide.

The final tally of what we have formed is

4.21 moles of potassium carbonate (K2CO3)

4.34 moles of carbon dioxide (CO2)

3.94 moles of carbon monoxide (CO)

These products have a combined heat of formation of – 6989 kJ while the reactants had a combined heat of formation of -4157 kJ. This means the fire fighting gunpowder generates about 2931 kJ per kilo of gunpowder which is similar to a conventional gunpowder.

The firefighting gunpowder makes only 8.57 litres of gas per kilo of gunpowder which causes it to have an explosive power of 563 x 103 L kJ kg-2 which compares with 839 x 103 L kJ kg-2 for normal gunpowder. I suspect that the lack of sulphur in the fire control gunpowder will slow down the reaction which will reduce further the explosive effect of this special gunpowder.

From my consideration of the firefighting gunpowder the change in the ingredients has caused the volume of gas generated to become lower. I hope that this example of stochiometry has been interesting.

Finally I need to give you all some advice,

The maximum penalty for making and experimenting with homemade explosives and fireworks is death ! I can accept no responsibility for any stupid experiment you choose to try at home. Some friends of mine once had a student who thought he would make an explosive, the student demolished a student flat and was killed in the explosion ! Learn from this man’s stupidity and do not repeat his error ! My advice is never to fool about with fireworks or to try to make your own.

On the subject of fireworks, here is some good advice for the next time you let some off. It is based on the British firework code.

  1. Only buy legal fireworks.
  2. Don’t drink alcohol if setting off fireworks.
  3. Keep fireworks in a closed box.
  4. Follow the instructions on each firework.
  5. Light them at arm’s length, using a taper.
  6. Stand well back.
  7. Never go near a firework that has been lit. Even if it hasn’t gone off, it could still explode.
  8. Never put fireworks in your pocket or throw them.
  9. Always supervise children around fireworks.
  10. Light sparklers one at a time and wear gloves.
  11. Never give sparklers to children under five.
  12. Never use petrol, E85, diesel fuel, paint thinner or other liquid fuels on a bonfire.
  13. Keep pets indoors.
  14. Look after your eyes. Fireworks are for a moment, eye injuries are for life !
  15. Don’t fool about with fireworks.

If you do want to fool with fireworks then please see this movie.

Liquid scanner

One other blogger has asked how well does it work ? (http://www.travelsupermarket.com/blog/liquid-x-ray-scanners-in-airports/) and is it going to lower security ?

A new device which can tell what the liquid is inside a bottle. It appears to work by looking at absorption at different wavelengths of X-rays.

If you look at a graph of absorption for an element such as lead against photon energy there are some peaks due to excitation of the electrons in the atoms. The only problem is that the X-ray photons for elements such as carbon are very low in energy and are unable to pass through air, I am not quite sure of how it will work.

I think that the machine needs to be able to measure the carbon, hydrogen and oxygen concentrations in an object if it is to be able to tell the difference between tea and vodka.

One alternative would be to use a pulsed neutron source combined with an energy dispersive gamma ray detector, this allows for a series of different elements to be measured. I have read how the US military use such a device to identify artillery shells which contain chemical weapons.

Many explosives (TNT, picric acid, semtex) contain nitrogen so one of the key reactions is

n + N-14 –> p + C-14 + gamma photon



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