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Hamburg airport

Dear Reader,

It has come to my attention that a irritant gas or aerosol has been released in the airport today causing the site to be closed down. One reports suggest that a pepper spray was discharged by “some clown” into the ventilation system. Some of my readers might want to know what is in pepper spray, these sprays are typically capsaicin and the other active chemicals in chill peppers in a solvent with a propellant to allow it to be discharged as a spray.

Capsaicin is quite a simple compound, here is a picture of a molecule of it.


DNA at home

Dear Reader,

It has come to my attention that in Germany some very strict laws exist against any DNA experiments outside “licensed sites”, for example the Daily Mail comments how people who do DNA experiments at home may now face three years of jail. I have to ask a question, “is it reasonable to ban all work on a particular field ?”.

Like it or not DNA experiments at home have been possible for over 20 years. Back in the early 1990s they were being considered in popular science magazines. Now for less than 2000 US$ you can get a home microbiology lab in which you can do DNA experiments.

My worry is that yes it might be possible to do some rather antisocial or criminal acts using DNA or DNA modification tools, but on the otherhand if we were to ban every tool which can be used to commit a serious crime then we will end up banning everything. For example I can make a quick list of some easy to misuse household items

cars, petrol (motor fuel), condoms, knifes, biro pens, matches, disposable pocket camera, cricket bat and water pipes.

Now in the interests of public safety I am not going to tell you how to do some very nasty things with these items, I am sure that many of my readers will spot quickly in this list some rather disagreeable possibilities but I think that the cost to the health, safety and welfare of soceity by banning these items would clearly outweigh their misuse.

The problem is that many tools can be used both for good and for bad, for example the uncommonly silly argument in Saudi Arabia against women driving includes.

3 – It also leads to women going out of the house a great deal, but their homes are better for them – as the Prophet (peace and blessings of Allaah be upon him) said – because those who love to drive enjoy it very much, hence you see them driving around in their cars here and there for no purpose, except to enjoy driving.

OK one can argue even from a nonislamic point of view that aimless driving is wrong as it results in needless air pollution, but it is unreasonable to ban the use of a tool which has many legal and good uses because it is possible to use it for evil purposes. For example maybe if someone who is not as nice as me ended up with this computer they could be blogging with it right now on rather nasty topics. They could be writing hate speech or very obscene poetry.

Equally a woman could drive a car to enable her to go and visit the hospital, members of her family or her place of lawful employment rather than somewhere where she might commit an illegal or immoral act. I know in Saudi Arabia that they take a very harsh line on theft, one might have to consider the question of should they ban all driving as a person might drive a car to a bank, rob it and then drive away from the bank with the stolen money.

There does come a point where we have to regulate some items as they have extreme misuse potential, keep in mind that a gun is a length of metal tube. A 44 revolver has a bit more than just a length of tubing but at its core it is a bit of pipe. A shotgun is even more simple. It has very few moving parts and it is a length of steel pipe fixed to a lump of wood, it is also an item with clear misuse potential. I can think of quite a few different types of crimes you can commit with a gun.

Well to get started we have vandalism, armed robbery and murder. I am sure that my readers will be able to imagine some other misdeeds which can be committed with a gun such as illegal hunting (poaching) but we are not here to make a long list of misdeeds. But it should be clear to the reader that while a case can be argued for banning or restricting some metal pipes like the 9mm UZI, the AK47, the Tec-9 and some others, it would be unreasonable to ban all metal pipes. For example I live in a house which has metal water pipes which deliver drinking water and hot water which heats my house.

Equally it would be reasonable for Germany to ban home experiments with some classes of cells and microbes, for example Yersinia pestis (black death), Bacillus anthracis (anthrax) Spanish flu and some other nastys. I could even accept as reasonable a law which banned all experiments other than those with a whitelist of organisms.

Burning bras ?

Dear Reader,

It has come to my attention that Gwyneth Paltrow now suggests that ladies should ignite underwear and bras which were given to them by ex-lovers at night in the light of a full moon. To my mind it is the height of sillyness. What about the negative effects on them if they manage to spark a forest fire or even just a fire which wipes out next door’s garden. Trust me I would be mad with rage if someone near me wiped out my garden with their midnight bra burning ritual.

But as a man who likes to be inspired by the likes of “Don Myers G8AYG” who was accused recently by one Prof I know of having been a “Real scientist”, I refuse to be intimidated by even the greatest nonsense in life. I hold the view that I have a duty to society as a whole to call out nonsense and to point out pseudoscience. I also noticed that Gwyneth has a lingerie shop, so adding a new dimension to the matter.

If women destroy lingerie then they will need to buy more to replace the burnt items, anyone who owns a lingerie will have the potential to make more money if women burn lingerie which they own.

I would like to point out something that rather than “Watch intently as the pieces burn. Know that your past is recycling into the ethers, liberating your future.” (step four of her bra burning ritual) you are polluting your lungs and the common air with polycyclic aromatic hydrocarbons, soot, carbon monoxide and other nasties. Also you will be releasing carbon dioxide which is a greenhouse gas.

I would also like to point out that todays bras are not designed for burning. Now most mornings on my way to work I walk past a shop (Hunkemöller) which sells ladies underwear. Trust me I am in too much of a dash to get to Chalmers to experience the joys of working in IMR / KK to stop and look at the shop yet alone wait for it to open in the morning.

Sadly I do not think that a bra comes with a detailed list of the polymers inside it or information on what will happen if you burn it. I think that the average customer is more interested in wearing them when they buy them rather than thinking about burning them.

After considering the idea of burning a bra I wondered what sort of fabric it might contain, rather than going to somewhere like Hunkemöller and then having to get pyro-GCMS done on many samples from the items. I have chosen to do some guesswork. The first thing I wondered about was lycra. It is a combination of polyether and polyurethane. As polyurethanes are very nitrogen rich I have to consider if the combustion is rich rather than being lean it might form hydrogen cyanide.

Also we should consider the larger organic products of heating lycra, I have checked the literature (Sandeep Khatua and You-Lo Hsieh, Journal of Polymer Science A, 1997, 35, 3263) and one grade of Lycra is made from the polyether made from butane-1,4-diol (Mn = 2000) and diphenylmethane-4,4′-diisocyanate (MDI) which is then chain extended with ethylene diamine (1,2-diaminoethane). This is a polymer product which has soft sections (the polyether) and the other part (PU) is the hard part of the product. As the product is largely this soft polymer I choose to first consider the degradation of this soft part. I could not see the potential for the formation of anything which screamed “nasty” at me.

So I choose to consider the hard part of the plastic, I checked the literature and with the first paper I found a nasty. J.J. He, L. Jiang, J.H. Sun and S. Lo in / Journal of Analytical and Applied Pyrolysis 2016, 120, 269–283 indicated that during the pyrolysis of a hard polyureathane which has similar chemistry to the lycra grade I found that aniline and other aromatic amines were formed. I can tell you that these aromatic amines are unhealthy. So as a chemist I would advise you not to burn lycra under uncontrolled conditions where you can not be sure that an excess of oxygen will be present.

If any of my readers know that a bra or some other item contains a particular polymer then please contact me, I can have a go at considering what will happen if we heat the polymer to the point at which it starts to degrade chemically.

Nutter on the tube

Dear Reader,

This morning much to my irritation there was a computer malfunction in my home, a computer was refusing to talk to the DNS (Domain Name Server) via a particular wireless network. I tried the test of using that network to visit a web site I have never visited before using my laptop. This is to try to work out if it was the computer or the network which was at fault. I then saw a truly horrible story.

A drunken thug pushed a man off a tube platform onto the track, he was later jailed for ten years. Judge Richard Hone QC said: “What you did, as you can see on the CCTV, was really shocking. You must have foreseen and been determined to cause serious bodily harm”. I have to agree with Richard Hone that this was a terrible act something which is truly unacceptable.

I think that the drunken thug should consider himself lucky not to have been convicted of a more serious offence (murder). Twice in my life I have arrived at a railway station shortly after a person has fallen under a moving train. When I was a second year undergraduate at Imperial College I once went to the Turnham Green tube station to start my journal to IC. I saw a great circus of activity at the tube station including a HGV marked with something which as “Emergency Passenger Services”. I later that evening asked a railway worker at the tube station what had happened, he told me that a person had been run over by a train and sadly they did not survive. The other time was in my first year in Sweden when at about 06:15 someone decided to jump in front of a X2000 high speed train, this event closed down the whole of the railway station so I had to make alternative arrangements to get to work.

Now what has happened in this film is that the victim was thrown off the platform he bonced off the -200 volt rail which is between the two rails on which the wheels go and he lands in the safety trench. I have to admit I winced when I saw him strike the live rail.

If you ever find yourself on tube track keep in mind that if you land in the safety trench then the safest action may well be to remain there keeping away from any rails. It may be best to wait until a railway worker helps you out off of the track. What ever you do, do not touch the live rails as you climb out. I winced a second time when the man used the -200 volt rail as a hand hold as he pulled himself up. He was very lucky to be wearing rubber shoes and not to touch anything else as he pulled himself up.

I would like to warn you that while at 200 or 400 volts rubber shoes can offer some protection against electric shock, they are useless if you touch something else at the same time as you touch the live conductor. Also at high voltages such as 10000 volts rubber boots tend to conduct electricity with ease. It is important to note that many rubber products contain carbon black as a pigment and this increases the conductivity of these items a lot. So never trust a normal rubber shoe or glove with high voltages.

In Sweden the overhead power wire is at about 15000 volts while in the UK it is normally at about 22000 volts. While the UK uses 50 Hz AC the Swedes use 16.6 Hz for railway supplies.

If you find yourself on a railway track without a trench such as a normal overground track with wooden or concrete sleepers, then it is very important to get out of the gap between the two running wheels. I have been told by a railway worker that there is never much clearance under a train, he told me that the most important thing if you are in a tunnel doing work and you hear a train coming is to get out of the gap between the running rails. He even advised that as a last ditch measure you should lay face down between two rail tracks but never on top of the sleepers.

I have never had to do this, and I sincerely hope that neither you or me have to do so. I imagine that by staying away from railway track (not crossing at unapproved points) that you will greatly reduce your chance of being run down by a train. I also do not know if the British railway worker who told me about 20 years ago was well informed or not so I would not want to trust his advice about sheltering between tracks, but looking at the front of a train I suspect that he was right that it is impossible to shelter between the rails on top of the sleepers. If any railway workers are reading I would value their thoughts on this issue.

Supply and demand

Dear Reader,

It has come to my attention that Trump has decided that the USA will impose a 20 % tax on all goods from Mexico. Now before we get going I am not going to enter a debate today on the moral issues, I will simply consider the effect on the market of goods in the USA and Mexico.

Now many of you have heard of supply and demand curves, this is often misunderstood there is no “supply and demand” curve. Instead there are two curves, a supply curve and a demand curve.

Now if we consider the supply first, you should understand that the higher a price is then the more people are willing to sell a product. As a result the higher the price of the item the greater the supply of the item to the market will be.

We can express this as

Amount for sale at price x = S + K’x

We can consider the buying of a product, now in a simple world the cheaper the price then then more people who are willing to buy the product. We can express this as

Amount which will be consumed at price x = C – (Kx)

If we combine the two equations then we can get the equilibrium price for an item.


A = S + k’x

A= C – kx

Subtract one equation from the other to give us

0 = (S-C) + [x(k’+ k)]

C-S = k’x + kx

(C-S)/x = k’ + k

1/x = (k’+ k)/(C-S)

x = (C-S)/(k’+ k)

This allows us to get the point at which the two lines cross, this allows us to work out the price of the product.

If we take some made up values then we get the following graph. Amount is on the y axis and price on the x axis.


The values I used were k = 1, k’ = 1, S = 0.2 and C = 3.2 which gives us a value according to my equation of 1.5 for the price. Either the supply or demand equation will give us the same answer of 1.7 units per time period.

Now we have done the simple case we will try a little harder and consider adding tax to the system.Lets start with a fixed amount of tax per item such as a fixed tax in pence per bottle of beer.

Now an ugly way of doing it is to write.

C-S = (k’x) + [k(x+T)]

This will make a mess as it makes it harder to find x from the five constants. A better way is to calculate a new value of C from the value of T and K. In this simple model the equation for consumption is

A = C – kx

Now we can add the tax effect

A = C – (kx + kT)

We can rearrange this to give us

A = (C-kT) – kx

Now we can start again with our equation writing

A = S + k’x

A = (C- kT) – kx

0 = S – (C – kT) + (k’x + kx)

0 = [(S + kT) – C] + (k’x + kx)

-[(S + kT) – C] = (k’x + kx)

C – (S + kT) = (k’x + kx)

[C – (S + kT)]/x = k’ + k

1/x = (k’ + k)/[C – (S + kT)]

x = [C – (S + kT)]/(k’ + k)

If we keep T at a constant value we will get a new demand curve, here in the following graph I have shown the extra line. What we now see is that the we have a new curve, this shows that the consumption of the product is now lower. With a tax (T) of 0.3 the price which the seller sees will be 1.35 while the buyer sees a price of 1.65.


Also consumption will have been reduced from 1.7 to 1.55 per unit time. Now we are selling less both the producer and the seller are having not such a good time as they used to have.

Now we can make a graph of the amount of a produce which sells as a function of the tax and also the amount of tax money that the goverment make. You should see very quickly that tax can serve two purposes, it can serve the purpose of making money for the goverment and it can also be used to discourage the purchase of an item. It is important to note that the amount of tax required to make the most money is smaller than the amount required to do a better job of discouraging consumption. I have included in these graphs areas of negative tax to show what happens if the goverment use a subsidy to encourage spending on an item.


Now here is the same data with the tax expressed as the percentage of the net price.




Sex toy inspection

Dear Reader,

It has come to my attention that the Swedish chemical authority have decided to inspect some items which might be known as “adult toys” or “sex toys”. I do have a problem with this use of the word “adult” as some of the things in “adult entertainment” sector are anything but adult. To me adult means mature, sensible, reasonable and decent. The true meanings of these four words “mature, sensible, reasonable and decent” are often polar opposites of some of the things in the “adult entertainment industry”. But I think that we will leave this topic alone.

What Kemikalieinspektionen did was to consider a total of 44 items from 16 compaines, now I am not going to discuss the intended use of the items or what they are. If you feel the urge to read that then I suggest you look elsewhere. What I am going to discuss is some of the chemistry involved.

Now the Swedish body choose to consider “phthalates, short chain chlorinated paraffins, azo dyes, nickel and the metals and flame retardants that are restricted for electrical products“. While the topic and the items might be controversial I think that it was a reasonable choice to make.

Now the start of the method explains how XRF was used to screen for a range of harmful metals, it will also detect bromine. But care needs to be taken with the measurement of bromine by XRD as one of the L lines (1.48043 1.48043 1.52590 keV) for bromine are very close to the line for aluminium (K lines at 1.48670, 1.48627 and 1.55745 keV). The items which were regarded as being interesting were then sent for further examination.

The problem with the report was that it was not totally clear which analytical method was used to determine the metal or the organics in the items. What was found in one study by Gerald Fowles which is mentioned in the wonderful book “Chemistry in the Marketplace” is that the nature of the mechanical pretreatment before leaching will alter the amount of a metal which can be released from an item. The key message is that chewing a plastic children’s toy was very effective as a means of releasing the metals in them while other mechanical pretreatments tended to lock in the metals. Also sucking on toys is not that dangerous but chewing and gnawing at them does release cadmium.

He also found that the use of hydrochloric acid which contains mercury(II) chloride as a preservative also inhibited the release of cadmium from cadmium sulfide and cadmium selenide. The reason is that an even more insoluble layer of the mercury chalcogenide will form on the surface of a pigment particle thus preventing any further reaction. It is a bit like the problem of sulfuric acid and marble chips, there a layer of insoluble calcium sulfate forms on the marble chips thus preventing any further reaction from occuring.

Gerald Wilfred Albert Fowles also did some very interesting work on lead and chromium in children’s comic books when he was at Reading University in the 1970s. In Diana F. Eaton, Gerald W. A. Fowles, Michael W. Thomas, G. Brian Turnbull, Environ. Sci. Technol., 1975, 9 (8), pp 768–770 he reports on how much lead and chromium can be leached from comic books when they are leached in a simulated stomach acid.

A different approach would be to use a wet combustion of the plastic by digesting it in a Parr bomb with nitric acid. Here the plastic would be totally degraded by the oxidant (nitric acid). Then we would get all of the metal contents released from the object. It is interesting to note that simple burning can result in the loss of some semivolatile metals such as lead.

What would have been interesting to know is if the items were leached with some chemical reagent or were they digested / burnt to release the entire inventory of the metals. One interesting problem is that while when PVC and latex are heated under oxidizing conditions that they are converted totally into gases, when silicone is burnt it forms a large amount of silicone dioxide. It is possible that attempts to liberate metals from silicone objects will be hampered by the formation of silica. In the worst cases the silica may form a crust over the metals thus locking them in.

Electrochemistry calculations (redox potentials and cells)

Dear Reader,

I was recently teaching some electrochemistry to some students, now before we get going it is important to note that the conventions on writing electrode potentials changed years ago. So if thou gets one’s ye olde text book out or ye olde almanack of chemie be ready for some possible problems.

For example in the 1950s paper on plutonium redox chemistry by Sherman W. Rabideau and  Joe F. Lemon, Journal of the American Chemical Society, 1951, 73, 2895-2899 the redox couple for Pu(IV)/Pu(III) is listed as being -0.953 volts vs the standard hydrogen electrode. Now in modern text books it is listed as about + 0.95 volts. This modern use is an example of the “European” convention while the example I gave as an example of the “American” convention. I would say that both are equally valid but if you want to do a redox calculation be careful that you do not mix unwittingly mix data from both conventions up.

I have not seen the american convention being used much in modern text books, but please be aware that it does exist.

OK Health warning over lets get on with some chemistry. Now as a brain teaser (or brain expanded) I asked my students to consider the question of will a solution of iron(II) tend to reduce a solution of plutonium(IV) to plutonium(III) thus forming iron(III) in the process.

Now the redox couple of iron(II) / iron (III) is +0.77 volts (European convention). So we can calculate the cell voltage for our cell under “standard” conditions (1 mole per litre of everything, at 25 ºC and 1 bar).

We can combine the following two half equations

Fe2+ → Fe3+ + e

e + Pu4+ → Pu3+

To give us

Fe2++ Pu4+ → Fe3+ + Pu3+

The emf of the cell will be under standard conditions equal to 0.18 volts, but which thing will be reduced and what will be oxidized. The plutonium couple is higher (more positive) than the iron one in our European type text. So the plutonium will tend to oxidize the iron to form plutonium(III).

We get the emf of the cell from the difference between the two redox couples. All redox couples are expressed relative to hydrogen gas / hydrogen ions in 1 M acid. This choice of standard is simply a convention. Like the Greenwich meridian we need some arbitrary point to call zero. Hydrogen is a good choice as it features in so many reactions.

From the value of the emf of our cell we can get the ΔG of the reaction, to do this we use the following equation.

ΔG = -nFE

n is the number of electrons which are transferred in the cell reaction (1) and F is Faraday’s constant (charge on a mole of electrons) which is equal to 96485 C. Using this we can get a value for the Gibbs free energy of the reaction. Keep in mind that a cell with a positive emf is a cell which is able to do work, thus ΔG for the reaction in the cell must be negative.

This works out as -17367.3 joules per mole.

We can now get the equilibrium constant for this reaction, when a cell has a emf of zero then it has reached equilibrium. Now we need to use a different equation.

ΔG = ΔGº + RT Ln Q

In our case

Q = aPu3+ aFe3+ / aPu4+ aFe2+

Now in the ideal world (nice place I wish I lived there) the activity coefficient is equal to one, the closest we get to an ideal world is a dilute solution. So for nice and dilute solutions we can write

Q = [Pu3+] [Fe3+] / [Pu4+] [Fe2+]

If ΔG = 0 (zero) then

ΔGº = -RT ln ([Pu3+] [Fe3+] / [Pu4+] [Fe2+])

Rearrange to

-ΔGº / RT = ln ([Pu3+] [Fe3+] / [Pu4+] [Fe2+])

exp (-ΔGº / RT) = ([Pu3+] [Fe3+] / [Pu4+] [Fe2+])

Now do the maths

exp (7) = ([Pu3+] [Fe3+] / [Pu4+] [Fe2+]) = k

Now k = 1107

we can rewrite the equations to give us

ΔGº = -RT ln k

Now it should be clear to my readers that a solution of iron(II) will reduce tetravalent plutonium into trivalent plutonium. You might be interested to read that the classic method of adjusting the oxidation state of plutonium from +4 to +3 in the PUREX process is to use ferrous sulfamate.

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