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SSM and ISA

Dear Reader,

Those of you who live in Sweden may have heard of a body called SSM (StralSakerhetsMyndigheten), this is a state body in Sweden which has the task of protecting people and the environment from the adverse effects of radiation both today and in the future. In common with the now defunct NRPB their task includes X-rays, “Nuclear” radiation (α, β, γ and neutrons), radiowaves (cell phones etc) and UV light.

One of the great problems we as a society is that for the good radiological protection of future generations living far in the future we need to make predictions based on experiments which only last a short time.

One important issue is the formation of organic complexing agents in low and intermediate level radioactive waste. If a substance forms which is able to bind to metals and form water soluble complexes which do not bind to mineral surfaces then the rate at which radioactivity leaks out of a waste store could be increased.

One such compound which has been considered by many people is isosaccharinic acid (ISA) which is formed from cellulose when it is exposed to calcium hydroxide. The cellulose can come in the form of wood, paper or cloth while many cements contain calcium hydroxide.

The classic way to make ISA is to treat lactose with calcium hydroxide, I have done this several times and the mixture soon turns brown and after boiling it down you are rewarded with a dark brown mixture which smells strongly of cooking. By careful filtration of the dark brown mixture a brown solution can be obtained which is then evaporated to a dark solid. This is then extracted with water and recrystalized to give a white solid, due to the insolubility of the calcium salt of the alpha isomer of ISA this is possible. The calcium salt of the beta isomer is water soluble and stays in the mother liquor with a lot of other compounds.

As a result it is relatively easy to obtain alpha ISA, the beta ISA is harder to obtain, so as a result almost all work done on ISA has been done with the alpha isomer. As the properties of the two isomers are not exactly the same it may not be safe to assume that alpha ISA can be used to model a mixture of alpha and beta ISA. Within this project we will explore beta ISA and determine if it poses a special threat in nuclear waste stores.

Now you might wounder why I mention SSM, the reason I mention them is that they are funding this research. One of the ways that SSM protect society is to fund research which allows them to make better predictions about the future. Now my SSM work is about to start, the plan is that I will try to publish papers as well as writing a report for SSM. I also want to bring you some updates about the work here on my blog.

Candlestick II

Dear Reader,

I took my candlestick to work and I quickly found it was radioactive, it was emitting beta particles according to a quick check with a contamination meter. As it was emitting that nice yellow/green light when exposed to UV light and it was emitting beta particles I quickly decided it was genuine uranium glass.

The next step in the characterization of the candle stick was to use gamma spectroscopy on it, now before we get going I would like to point out that gamma spectroscopy is not a press the button and get the result type of machine. For those of you who are proper traditional chemists / scientists you will be aware that for a new type of sample it is very hard with most machines to create a method with a spectrometer where you just put in the sample and press go before getting the final answer.

One of the problems is the issue of self adsorption, for the lower energy gamma lines many of the photons will never escape from a large sample. The ideal sample for gamma spectroscopy would be a tiny spec (a point source) which would be at a well defined distance from the detector.

The candlestick is anything but well defined in distance from the detector and it is far from being a point source. I did not want to melt it down to make a lump with a more simple shape so I decided that we should measure it in its native form.

One of my questions about the candle stick was “is the uranium a depleted uranium, or is it a natural uranium which is likely to predate the nuclear age ?”

I reason that as DU is less valuable than natural uranium it would be the logical uranium to use if you were making a uranium glass candlestick in the 1950s or later. But if it was a more early candlestick then it would be more likely to have a natural isotope signature for its uranium.

We need to consider three uranium isotopes

238U which is the bulk of natural uranium, this does not have any useful gamma lines but its daughter (234Th) which emits gamma rays, as the half life of 234Th is short when compared with the age of the candle stick it can be treated as an extension of the radioactive decay of the parent 238U. 70% of the 234Th will decay to the meta stable state of 234Pa (234mPa). It is important to note that the 234Pa (both forms) give a forest of gamma lines (hedgehog spectrum).

Nuclide Half life Decay mode Main gamma lines
238U 4.468 x 109 years alpha No gamma
234Th 24.1 days beta 63.3 (4.8 %), 92.4 (2.8 %) and 92.8 (2.8 %)
234mPa 1.17 minutes beta 258.3 (0.73 %), Hedgehog spectrum
234Pa 6.7 hours beta Hedgehog spectrum

 

If the uranium had been a depleted uranium then I would expect that almost all the 234U and 235U would have been removed. As the 234U has a long half life it serves to block the decay chain of 238U if the sample is not old on a geological time scale.

I reasoned that by looking for the decay products of 234U that I could test the hypothesis that the uranium was a prenuclear age natural mixture of isotopes.

This uranium will decay to form a long lived radium (226Ra) which will then slowly on the timescale of the candlestick’s age decay further.

234U –> 230Th –> 226Ra –> 222Rn –> 218Po –> 214Pb

Nuclide Half life Decay mode Main gamma lines
234U 245500 years alpha No gamma
230Th 75380 years alpha 67.7 (37 %)
226Ra 1600 years alpha 186 (3.6 %)
222Rn 3.8 days alpha No gamma
218Po 3.1 minutes alpha No gamma
214Pb 26.8 minutes beta 242 (7.4 %), 295 (19.3 %), 352 (37.6 %),
214Bi 19.9 minutes beta Forest of lines
214Po 0.1643 ms alpha No gamma

 

The 214Pb will decay by beta emission to form 214Bi and then 214Po which then decays to form 210Pb. As after 226Ra no nuclide has a half life longer than a few days until you reach 210Pb we can treat these decays as extensions of the radium decay if we make a kinetic model of the candlestick.

The fissile 235U does have a useful gamma emission of its own, this can be used to confirm if the uranium was natural or depleted.

It will decay by alpha emission according to the following mechanism.

Nuclide Half life Decay mode Main gamma lines
235U 703800000 years alpha 109 (1.5 %), 144 (11 %), 163 (5.1 %), 186 (57 %), 205 (5%),
231Th 25.52 hours beta No gamma
231Pa 32760 years alpha Forest of lines
227Ac 21.773 years beta No gamma
227Th 18.72 days alpha Forest of lines

 

I hope to now be able to go through the spectrum and then hunt for lines, I recall that the 186 keV line for 235U was present. So far I think the uranium is from before the nuclear age.

Uranium glass

Dear Reader,

For some time I have been looking for some uranium glass, this is a type of glass which contains uranium. because of the uranium it is green in colour. The glass also fluorescent, when exposed to UV light it emits green light. I was in a second hand shop today and I spotted some green glass, I happened to have a long wavelength UV light in my pocket so I did a quick test of the glass with UV light. As the 20 SEK candlestick emitted green light I bought it.

I have made a short film of the candlestick being exposed to UV light. I hope to upload to youtube soon a film of the candlestick in a dark room being exposed to a UV light which I turn on and off.

20 SEK (circa £ 2) candlestick made of uranium doped glass

20 SEK (circa £ 2) candlestick made of uranium doped glass

I also hope to take the glass candlestick to work and measure its radioactivity. When I do I will post the details in another blog post.

All Things Bright and Beautiful

Dear Reader,

It has come to my attention that the BNP have released a bigoted song using the tune of “All Things Bright and Beautiful”, this is a horrid thing. To my mind the song “All Things Bright and Beautiful” is a celebration of all things which are bright and beautiful. To my mind their use of the tune is like defacing an attractive oil painting with roofing tar.

I hold the view that the BNP are bad for british society.

What is solvent extraction ?

Dear Reader

You might ask the questions of what is the liquid-liquid extraction of metals and why is it important ?

I would say that the liquid-liquid extraction of metals is the more correct term for what is normally understood as “solvent extraction”. Solvent extraction is not the extraction of a solvent from a thing, but instead it is the extraction of a substance from one solvent into another. Commonly one of the liquids is water but there is no reason why the ideas of solvent extraction should not be applied to non aqueous systems such as silver being extracted from molten lead into molten zinc or the extraction of an organic species from methanol into hexane.

A typical metal ion in an aqueous phase is bonded to water molecules and/or chloride anions, this forms a water soluble metal complex. The metal complex normally has a very low solubility in an organic layer, but like many rules some exceptions do exist.

For example osmium(VIII) forms an organic soluble oxide (OsO4) which can be thought of as having formed from a Os8+ cation and four water molecules. The waters would have bonded onto the osmium before undergoing hydrolysis to hydroxyl ligands (OH-) which then react further to form oxide ligands. I suspect however that [Os(H2O)n]8+ is an impossible complex for several reasons so I do not think it will be possible to make it.

But I know that compounds such as [OsO3(OH)2] are well known, and this can be thought of as a hydrated form of OsO4, or alternatively OsO4 can be viewed as the acid anhydride of [OsO3(OH)2]. Yet another alternative is to stop thinking for a moment about osmium and then move onto some other things.

Well back to the solvent extraction of metals, if we take a hooks and eyes view of chemical bonding the electron poor metal ions can bond to the electron rich parts of solvent molecules such as the oxygens in water. These bonds to water can be broken and replaced with bonds to molecules with big long fatty groups, for example charged cobalt atoms in water are normally found with six waters around them. For example using 3D x-ray crystalovision (known to chemists as X-ray crystallography) we can glimpse a charged cobalt bearing six waters in the way it is thought to be in aqueous solution.

Cobalt with six waters

Cobalt with six waters

This cobalt ion was seen in a paper by some gifted chemists who made coordination complexes with tetrahydrofuran-1,2,3,4-tetracarboxylic acid.[i] I have to admire their compound, in some ways I wish I had done that chemistry myself.

Now it is well known that cobalt(II) salts in dilute water solutions are pale pink in colour, this is a sign that the cobalt is in a octahedral complex with six waters attached. However under some conditions deep blue complexes of cobalt are formed, this is normally a sign that a tetrahedral complex of cobalt as formed. It is well known that the solution of cobalt in bis-2-ethylhexyl hydrogen phosphate in a hydrocarbon solvent is deep blue. This made me want to look to see if X-ray crystallography has ever been used to characterize the idea mononuclear (complex with a single metal atom) of cobalt with two dialkyl phosphate ligands.

When I did the search I was in for a shock, I found a coordination polymer of cobalt and bis tert-butyl phosphate in which tetrahedral cobalts were linked by the dialkyl phosphates into a 1D chain. I also found bis-(((4,7,7-Trimethyl-3-oxobicyclo[2.2.1]hept-2-yl)phosphinato)-((4,7,7-trimethyl-3-oxobicyclo[2.2.1]hept-2-yl) hydrogen phosphinato))-cobalt(II) which is made from one cobalt(II) ion, two molecules of bis-(4,7,7-trimethyl-3-oxobicyclo[2.2.1]heptan-2-yl) phosphinic acid and two molecules of the conjugate base of this rather long named phosphinic acid.

I looked in the Cambridge database for metal complexes in which two dialkyl phosphate ligands chelate to a single metal atom to form a complex. None were found, I soon concluded that the oxygen oxygen distance is too large as the phosphorus atom is tetrahedral, this is different to a carboxylate where the central carbon is trigonal planar.

Here are the XYZ coordinates of a typical model phosphorus compound

O(1) -1.368 1.517 -0.000
P(2) -0.171 0.647 -0.000
O(3) 1.160 1.562 -0.000
C(4) -0.185 -0.423 1.516
C(5) -0.185 -0.424 -1.516
H(6) 1.876 0.950 -0.000
H(7) 0.715 -1.078 1.517
H(8) -1.102 -1.054 1.516
H(9) -0.177 0.220 2.424
H(10) -1.091 -0.199 -2.122
H(11) 0.726 -0.221 -2.122
H(12) -0.199 -1.495 -1.213

 

The two oxygen atoms are 2.5 Å apart,  now we can compare the distance with that in acetic acid. Again here is the xyz table, and in acetic acid the oxygens are 2.2 Å apart which makes it much more easy to form a chelate ring.

C(1) -7.031 -0.130 -0.000
C(2) -5.522 -0.130 -0.000
O(3) -4.918 -1.176 -0.000
O(4) -4.853 1.029 -0.000
H(5) -7.403 -1.179 -0.000
H(6) -7.402 0.394 0.909
H(7) -7.402 0.395 -0.909
H(8) -3.910 0.796 -0.000

 

Now some of my readers may ask “what is a chelate ring”, the idea of chelation is where a molecule bonds to a metal with more than one atom. I would like you to do a thought experiment, we have gone to the beach and a fish has bitten my foot, now how do I remove it ?

I have to open its mouth and then I can pull it off and throw it back in the sea.

Now imagine that the crab has grabbed by foot, now to remove the crab I must release both of its pincers at the same time. If I remove only one at a time while I am dealing with the second one the first one will grab me again. The crab is able to chelate to me.

Things get even worse with a scorpion which has two front grabbers and a tail to grab with, and frankly if the octopus gets me with all eight tentacles then it is going to be very hard to escape from its grasp.

If a ligand is able to chelate to a metal then it normally makes it very hard to remove the metal from the ligand’s grasp.

Thinking about the extraction of cobalt we might suspect that it should be given by the following equation

DCo = k[(RO)2PO2H]2[(RO)2PO2-]2

I suspect that the (RO)2PO2H will form hydrogen bonded dimers in the organic phase which could alter the equation to

DCo = k[{(RO)2PO2H}2]1[(RO)2PO2-]2

This might be true when the concentration of (RO)2PO2H is very low, the problem will be that when the concentration of (RO)2PO2H is high then it increases the dielectric constant of the organic phase, this will disfavor the extraction of the lipophilic (fat loving) cobalt complex [Co((RO)2PO2)2 ((RO)2PO2H)2]

This will make the equation which relates the distribution ratio closer to

DCo = k[{(RO)2PO2H}2]0[(RO)2PO2-]2 = k[(RO)2PO2-]2

As the concentration of (RO)2PO2- depends on the proton concentration we can make the equation slightly more complex and more useful.

As

Ka = [(RO)2PO2-][H+]/[(RO)2PO2H]

Then

Ka / [H+] = [(RO)2PO2-]/[(RO)2PO2H]

So

Ka [(RO)2PO2H] / [H+] = [(RO)2PO2-]

So next

DCo = k{[(RO)2PO2H]}2 ka2 / [H+]2

So

DCo = k{[(RO)2PO2H]}2 ka2 [H+]-2

This equation does explain how to change the distribution ratio by altering the concentration of acid, by making a change of pH we can adjust our D value. Now as my physics teacher told me we should use dimensional analysis to decide if the equation is good or bad.

Now DCo = [Co]organic / [Co]aqueous

So the D value has no units

So the k value has the units of mol-2 dm6 as [(RO)2PO2-] has the unit of mol dm-3

OK what next.

Ka has the units of mol dm-3

So we have

mol-2 dm6 . mol2 dm-6 . mol2 dm-6 . mol-2 dm6 = mol-4 dm12 . mol4 dm-12 = mol0 dm0

Which finally confirms that the equation

DCo = k{[(RO)2PO2H]}2 ka2 [H+]-2

Is a viable equation which is at least mathematically correct.

At this point I think we can call it a day and have another solvent extraction lesson another day.


 

[i] Liang-Fang Huang, Chang-Chun Ji, Zhen-Zhong Lu, Xiao-Qiang Yao, Jin-Song Hu, He-Gen Zheng, Dalton Trans, 2011, 40, 3183.

Elk River spill III

Dear Reader,

What is safe ?

This is a good question for us to ask. Recently in the US a coal washing plant accidentally spilled a large volume of 4-methyl-1-hydroxymethyl cyclohexane into the Elk river, now while I do not like water which is tainted with something I have to ask how safe / dangerous is it.

I was interested to see that a Midwife (Lesley Rathbun) in the US has been quoted as saying “Nobody knows what this chemical is or what it can do, or how much is not good. Pregnant women have all sorts of things they can be worried about when pregnant, and they have to have some sort of trust in the state and federal agencies.”

I have emailed her to ask why she is concerned about this chemical to see if there is something about it which causes her to be concerned about it, and I am awaiting her reply.

Lets look at this short quote and take it apart and examine it.

  • The statement that “Nobody knows what this chemical is”

This is a statement which can be understood in several ways, if we use super formal English then this is a statement which suggests that no person on this earth (above it or below it) knows what the chemical is that was involved in the accident. I think that this would be an unreasonable statement to make as it is already known what the identity is of the chemical which has been spilled is.

An alternative reading of the text is that “none of the general public have heard of the chemical involved in the spill”, I can quite believe this statement. Before the Elk river spill I have to confess that I had never heard of or considered 4-methyl-1-hydroxymethyl cyclohexane. I have less of an excuse than the typical member of the public as I have two degrees in chemistry and I am a docent in organic chemistry, but it is impossible even for docents to be able to have considered every possible molecule in the big wide world.

Well we can have a go at educating the public as to what this molecule is, so maybe we can do something about this first issue.

  • “or what it can do, or how much is not good.”

This is a great question which is caused by a lack of data, I have looked quickly at the molecule in question and the aldehyde / carboxylic acid which can be formed by oxidation of the alcohol group in the body. None of these compounds have a structural feature which screams out at me “toxic”, and a quick search of the literature suggests a general lack of knowledge about the substance. I would say that for an industrial product to have been used for some years and not attract the attention of the biochemists it is likely to be a substance with little if any biological activity.

If it was an acute poison then I would expect it to have been noticed as a result of an accident, the chances are that people have been splashed with the chemical and it has been fed to rodents, in rodents the substance does not seem to be very toxic and as no reports exist of human poisonings then I think we can conclude that it is not a quick acting poison.

I would also say that as no large scale fish kills have occurred in the river it does suggest that the chemical is not toxic.

Longer term exposure is harder to deal with, also the problem exists that in todays society routine toxicology testing on animals is not socially acceptable. I also feel unhappy about the idea of doing animal experiments with every chemical in existence just to obtain the data. To my mind the work cannot be justified, the use of animals in research must be restricted to experiments where it can be argued that a clear need exists for the data and that no non animal alternative exists.

Now as I can not find any sign of the CDC work on the substance which suggests that it is “safe” then I can not make a judgement of how good the work is, but right now I can see a case for testing the chemical with cell lines or with bacteria / yeasts in things like the Ames test. Looking at the compound I think that it will not be a mutagen according to the Ames test, even if you include the mashed up rats liver which will give you metabolic activation of some carcinogens. Some carcinogens are in reality precarcinogens, they need to be activated by the body to form the thing which induces cancer.

While the Ames test is not perfect (some false positives and false negatives do occur) it is a good test for carcinogens which act by damaging the DNA. The majority of carcinogens act by harming DNA thus making it a good screening test.

I would also say that maybe some testing with pregnant fish could be justified to find out if the substance which humans have now been exposed to at trace levels is able to pose a reproductive threat. I would imagine that the Zebra fish would be used for such an experiment. The fact that the substance does not appear to kill adult fish will make it slightly more easy to test it for reproductive effects in fish.

  • “Pregnant women have all sorts of things they can be worried about when pregnant”

This is a rather grey statement, a woman can worry about all manner of things while pregnant. Some of these things are perfectly valid things to worry about, I hold the view that a woman who is pregnant who needs radiotherapy for cancer of the cervix should consider the real threat to her baby much more than the woman who is concerned that laughing at a joke is going to cause her baby to change into an alien. Both are things which a woman could worry about but I have chosen two examples from opposite ends of the spectrum of how serious a threat they are to a fetus.

  • “and they have to have some sort of trust in the state and federal agencies.”

I hold the view that both the state and federal agencies should exist to serve the needs of the citizen, but serving the needs of the citizen does not mean that the agency should attempt to ban everything in an attempt to make the world a safer place. While some substances and activities should be restricted or even banned, a ban should not be imposed without good evidence or at least solid reasoning.

The idea of banning a chemical because it has a funny smell is not reasonable, I would say that no relationship exists between how offensive the smell is and how harmful a substance is. I can think of plenty of nasty things which either have nice pleasant smells (or no smell) and plenty of chemical sheep in wolves clothing which stink to high heaven but are quite harmless.

I also think that if the state starts to suffer from banamania (mania for banning things) then the citizen will suffer as medical products will be impossible to obtain and also employment is impossible to obtain as every job requires some chemicals. For example a school teacher needs a stick of calcium sulphate (blackboard chalk) which they use to write on a slate board (old fashioned blackboard). While you can replace the blackboard with some modern electronic white board smart board gadget this will require a far wider and more complex array of chemicals to make it and to operate it. So if we ban all “chemicals” then we will not even be able to write on the blackboard.

Furthermore the citizen will suffer under banamania when many household products are outlawed, for example in Sweden we make great use of glass fibre to keep our homes warm. Without the glass fibre the house would be much harder to heat and also if we take the glass from our windows things are going to get rather disagreeable in winter. Part of me would like to challenge anyone who has banamania to sleep naked in my garden during the worst part of a Swedish winter without a sleeping bag, or maybe I should not as I do not want to have to deal with the paperwork with the local police which is required when frozen dead bodies are found on the lawn.

Trust me unless you have a very thick sleeping bag (made from “chemicals” you will die if you try sleeping outside in -20 oC winter.

So I hope that my reader can understand that banamania is not good for society, on the other hand a refusal or failure to ban some substances is equally bad for society. When I was a boy, I once saw a toy which would make most chemical safety inspectors very upset. It was a mercury maze, a plastic maze with a drop of mercury inside it.

Now regardless of what you might think about mercury, I strongly hold the view that toys containing mercury in this form should be illegal. Another household item I think deserves a ban is the very old home science kit which contained 106Ru and other radioactive sources.

Also it is important that the regulator does not serve the wants and desires of industry at the expense of the needs of the citizen.

The Elk river spill II

Dear Reader,

When I looked at the case of the Elk river spill I considered the question of where does the 4-methyl 1-hydroxymethyl cyclohexane come from, it is not as if the aliens land in the car park and hand over drums of the chemical to the humans (who are glad to get it). Instead it is made by the chemical industry, one route would be from the reduction of dimethyl terephthalate using hydrogen, while in the lab chemists like to use expensive reagents such as lithium aluminium hydride in cheap glass flasks in the bulk chemical industry they like to use cheap reagents such as hydrogen in expensive metal reactors.

S. Richard Turner, Journal of Polymer Science Part A-Polymer Chemistry, 2004, volume 42, page 5847 explains how dimethyl terephthalate is hydrogenated using a palladium cataylst to make dimethyl 1,4-cyclohexanedicarboxylate which is then reduced using a copper / chromium catalyst to make 1,4-cyclohexanedimethanol. This type of catalyst is reported to have some ability to do a hydrodeoxygenation reaction on an alcohol. But the Cu/Cr system is more well known for the hydrogenation of carbonyls.

I suspect that if some acid is present then the 1,4-cyclohexanedimethanol will dehydrate to form an unsaturated monoalcohol which can be hydrogenated to form 4-methyl 1-hydroxymethyl cyclohexane.

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