The Supersafe World of Chemistry

By: David Bradley

A few years ago, I was commissioned to design and describe some rather simple "science" experiments for an encyclopaedia to be published by one of the big publishers of such things in the UK.

It was great fun, demonstrating with a dollop of butter - or low-fat spread for the health conscious - a child's plastic beaker, an old tin camping mug and some hot water insulators and heat conduction, that kind of thing. When it came to the chemistry experiments, the first and easiest to create, I foolishly thought at the time, would be the crystal garden. Little packet of copper sulphate crystals, a piece of cotton thread, a lead-free pencil and a tumbler full of water. How wrong could I have been?

I sent off the text - via floppy disk no less - quite advanced for a publisher that normally created rather non-technical stuff such as how to keep your aspidistras flying or crochet a bird-cage cover. And waited expectantly for commendation from the editorial team and the cheque in the post.

They liked the melting butter - they had even tried it and made a mess all over an old copy of the aspidistra booklet. Their "Scientific Advisor", however, had poo-pooed the idea of using copper sulphate.

I was stunned, remembering a time in junior school (3rd grade) no less when we grew a copper sulphate crystal garden on the quarry-tiled window-sill of the classroom and produced some stunning gems. Some were almost an inch long I seem to recall. When you are seven that's a pretty big crystal! What could be the problem? Maybe manufacturers had changed copper sulphate somehow since that time and it does not work so well any more?

 

No. It turned out that the Scientific Advisor simply could not allow the cupric salt to be used in the experiment. First off I thought it must be a question of cost. They would be giving away a few grams of the stuff with the encyclopaedia and if they could not get an educational discount it might cut into their profit margin a bit too deeply. I checked the pricing in Aldrich, or was it the BDH catalogue? CuSO4 did not seem too expensive, at least not for the less than generous amounts they planned on supplying so that was not it.

It transpired that the wonderful Ad-vis-or was scared that the kiddies doing the experiment would ingest said sulphur-containing matter and succumb to its terrible effects. I thought they must be joking, the part-work was aimed at 13-16 year olds not infants. (Admittedly, copper sulphate is toxic, but you get the point) "No. Copper sulphate is listed as a hazardous material you will have to think of something else less dangerous for our subscribers", they told me!

I thought carefully, what is so harmful about copper sulphate? Does it not just give you a case of the runs if you swallow a bit too much? No caustic effects, no rashes, no chain reactions set off in cytochrome respiratory enzymes, pretty safe stuff really unless you are very foolish and eat it like jelly beans, surely there was some mistake? Well, they had the pen ready for that cheque and the gas bill was due, so who was I to argue?

Alum - that will suffice, I thought, not quite so pretty but it does form large octahedral crystals so that would be quite impressive nevertheless on the kitchen table. It's less of a hazard than copper sulphate and quite handy to have around the house as a styptic. The publisher could even ask the chemical supplier to add a food dye, I thought, or we could even incorporate that step into the experiment to make it really exciting!

"No go," they said. What? "You'll have to come up with something even less hazardous than that". This was bizarre, I racked my brains...the only thing I could think of was the stuff my junior school teacher had suggested our using for the homework version of our crystal garden - magnesium sulphate. Wonderful, the kids would produce tiny, bland, colourless crystals if any at all.

Anyway, they went along with that - I did not bother to mention that magnesium sulphate is Epsom salts, a medicinal substance with infamous purgative properties, so any of the kids with a taste for crystals was in for a nasty shock. Of course, the experiment could now be deemed "safe" although the hazards were almost exactly the same as with the original bright-blue stuff I had suggested. The Ad-vis-or was happy though, his back was covered.

The experience reminded me of the first few months of the COSHH (control of substances hazardous to health) safety regulations, which would have us locking even the most innocuous materials, such as magnesium sulphate, in airtight containers under armed guard. Well maybe not, a visit to an undergraduate organic practical lab recently demonstrated that safety regulations, while providing unwilling penpushers with plenty of work, is all but disregarded by some laboratory technicians too busy chain-smoking over the flasks of ether to worry about anyone being stupid in their lab. The conc sulphuric was still at shoulder height above the bench and an open bottle of pyridine was left standing overnight in a faulty fume-cupboard that seemed to generate more noxious vapours than it extracted. The poor male undergraduates will be worrying (needlessly) about their gonads for years to come if they find out!

Surprisingly, the bottles of "copious" water were nowhere to be seen. This vital material is an essential component of any safe laboratory, viz. any spillage of "such and such" a chemical should be washed immediately with copious water. Of course, according to the early COSHH handbook - my office copy at least - this washing applied to every chemical that might be spilt. Postgraduate demonstrators around the country could be seen busily washing spillages of that most hazardous material "deionised water" with the ubiquitous copious water for fear of retribution at the hands of the lab tech.

Safety matters. Of course but standards do change and some rules, such as the copious water one are there to be broken. My A-level chemistry teacher used to brag of the days when she worked in industry and everyone washed their hands in benzene. As an undergraduate we swapped the benzene for acetone to get rid of those nitric acid stained fingers(!) after a particularly gruelling practical session. I dare say another solvent - soapy water or something equally as astringent and toxic - has superseded even this organic by now.

I must dash, the kettle has just boiled and I have a packet of hydrated CuSO4 to dissolve and a piece of thread to tie around a pencil... 


Elemental Discoveries

Issue 47

With a grain of salt

What do bags of rice, asteroids, a pile of salt and a sand dune have in common? They are all granular media, of course!

Collections of small solid particles, like rice, or grains of sand, behave in many peculiar ways, according to University of Stuttgart physicist Hans Herrmann. He and his collaborators Stefan Luding, also at Stuttgart and Raffaele Cafiero of PMMH, ESPCI in Paris, France, are building on earlier work by using statistical mechanics to understand many of the strange phenomena that occur in granular media.

For instance, they hope to explain the world's biggest sand dune - 'El Purpur', in Peru, as well as why brazil nuts always rise to the top of a carton of smaller mixed nuts. One of the team's most recent discoveries [[reported in Physica A: Statistical Mechanics and its Applications, 2001, 295, 93-100]] shows that granular media display a pronounced deviation from classical Boltzmann statistics in several important ways.

Liquids, the ultimate in granular media, generally follow Boltzmann's rules, but, with particles much bigger than atoms and molecules, a granular medium can behave sometimes like a liquid sometimes like a solid, so Boltzmann fails. Herrmann and his colleagues point out that granular media are dissipative systems, in other words, collisions between grains are inelastic so energy is lost when the system is in motion, such as might occur when wind blows across a sand-dune or when salt is shaken from a salt cellar.

In an ideal system, a statistical analysis reveals deviation from Boltzmann caused by clustering of particles in which the grains in a cluster are slower moving than those between clusters. Herrmann suggests an analysis using Constantino Tsallis' work might be the most lucrative in terms of increasing understanding.

Sam Edwards and Dmitri Grinev of the University of Cambridge describe an effect important not only in understand salt and sand dunes but in the handling of powders and other granular materials in the chemical and pharmaceutical materials - from explosive compounds to aspirin tablets.

Edwards and Grinev have alighted on the idea that a complete picture of granular media will not be possible without a better understanding of the transmission of stress between 'interacting' particles in the medium. They have developed a statistical-mechanical approach to deriving the equation which links stress to the packing geometry. The concept of how grains pack together is closely linked to how forces are transmitted between them. Their theory helps to explain experimental data on reversible and irreversible behaviour of vibrated granular media and, says Grinev, gives a clear physical picture of the compaction phenomenon.

So, next time you're tramping across the desert dunes or simply sprinkling salt on your meal…consider just how complicated tiny grains can be.


Elemental Discoveries

Issue 47

Lingua Franca

"After standing in the fridge overnight, we stirred the solution..."

The definitive scientific article is long-winded, convoluted and flowery. It is couched in jargonistic terms and pompous prose. It relies on the passive usage of tenses and formal syntactical, grammatical and punctatorial definition, phraseology and construct.

Well, that is what a proverbial scientist from another planet – Mars perhaps? - might think of the scientific literati were they to peruse just one or two of the countless, almost infinite stack of journals published round the world and on the web. Of course, each discipline must define and use its own terms and language. There is no point in every paper published having to redefine the wheel or in more native terms defining something as "simple" as what is meant by the term "covalent bond" despite the fact that a scientist outside the discipline might not know even in vague terms. Some papers though just stretch the point a little too far – and not a small number of them are found among the chemistry journals.

One area in which a scientist can rapidly alienate any reader regardless of their intellectual ranking is in the creation of acronyms and their associated concatenated nouns. In order to make a paper entirely opaque to the non- specialist most scientists will opt for the more the merrier attitude. Recently, one well-known chemistry journal published a series of papers covering the various advances in one particular field of spectroscopy, nuclear magnetic resonance. Fine, NMR that is reasonably well known even to non-chemists, although to appease the sensitivities of medics and biologists and the general public the use of NMR for imaging in hospitals tends to go under the name MRI thus dropping the "nuclear". I cannot think why...

While NMR, IR (infra-red), UV (ultra-violet), UV-VIS (visible – not really an acronym at all) might all be readily absorbed. One particular paper began waffling on about 1D NMR INADEQUATE. Huh? Not just an acronym but a mnemonic. But, aren't mnemonics meant to help the reader? To be fair, the technical editors at this particular journal tend to define the acronym at the first mention of such things in each paper, unlike several of their rival journals, which shall remain anonymous but they know who they are. In this instance it turns out that the acronym/mnemonic represents "one-dimensional nuclear magnetic resonance incredible natural abundance double quantum transfer experiment [spectroscopy]". See it is obvious now. I presume from this that the inventor of the technique had a somewhat weird sense of humour or at the very least a strange loathing for technical editors. Many readers will perhaps identify with the sentiment although it is badly misplaced.

Another related paper had NMR up for reckoning again, this time with INEPT and rather bizarrely SLITDRESS techniques being described. INEPT is perhaps what the technical editor felt when they could not find the definition. It is "insensitive nuclei enhanced polarisation transfer" while the lewd SLITDRESS is "slice interleaved depth resolved surface coil spectroscopy" for anyone who is not past caring by this point.

The concatenation of nouns and adjectives in this manner is what the late Robert Schoenfeld one time Editor of the Australian Journal of Chemistry described as a German vice! The Germans even have a specific term for it: Hauptwortkombinationenzusammensetzungsbedufnis. Makes the acronyms look easy! To make the most of Hauptwork...whatever, it is always best to pad out the acronym when spelt out in full so that the reader will be absolutely none the wiser. For instance, one might say "A slice interleaved depth resolved surface coil spectroscopy literature survey". The kind of thing not to do on a Friday afternoon.

It is on points of grammar that scientific writing can be best used to maximise opacity of a particular paper. For instance, when chatting in the coffee room one chemist might say to another, "We had an idea that the nitrogen was quaternary, so we boiled it up with acid and ran the spectrum..."

Fair enough, why not use something similar in the paper? Perhaps, 

"We suspected that the nitrogen was quaternary, so we heated the compound with acid and recorded its NMR spectrum..." A little more precise and fairly pleasant to read. However, chemists – with a few well-known literary exceptions - tend not to be satisfied with phrases that are so smooth and flowing – almost readable in fact. The sentence that would end up gracing the printed page would inevitably read something like this, "In order to determine whether the nitrogen atom centre was of a quaternary nature, the compound X was heated under reflux at atmospheric pressure in the presence of and acid and following exhaustive work-up the product extracted was then subject to examination with NMR spectroscopy to elucidate a definitive structure and conformational analysis..."

Aaaah, much better, n'est ce pas? There is, however, one area where chemists simply cannot simplify their prose without drawing a picture and that is in chemical nomenclature but even then some try to make things as easy(?) as possible. Whereas biotechnology has resorted to naming things in note form for instance hedgehog and sonic genes on the drosophila genome, chemists still have the likes of "After standing in the fridge overnight, we isolated the sample of {4,34-dimethyl- 1,4,7,10,13,16,19,22,25,28,31,34,37,40,43,46,49,52,55,5

-icosaazatricyclo[56.2.2.2.2.2.7,10,28,31,37,40]hexacontane using a supercritical mixed solvent system and subjected it to INADEQUATE NMR..."

Try figuring that one out after a hard day in the library...

Next month: redefining the simultaneous anachronistic non-syntactic deconstruction of tautological self-repetitious verbiage in the humanities...Not!

Bibliography

For a precise, concise and very useful guide to "writing proper" try the late Robert Schoenfeld's The Chemist's English, VCH, 1986, 2nd edn. Schoenfeld takes apart the English language in such a lucid way that there is literally no room for verbiage nor ambiguity once he has finished. You might spot one or two literal references from Schoenfeld in this article although please don't rush to tell me where the grammar trips up – no pedants illuminating my split infinitives non-hyphenated compound adjectives, pendant or dangling participles, pur-lease.

It would be nice to think Schoenfeld's book or at least part of it could make it on to the web at some stage where so much dodgy writing proliferates at a greater rate than in the scientific literature.

Additionally, David Lindsay's "A guide to Scientific Writing", Longman Cheshire, 1990, covers much ground in how to avoid the common pitfalls of jargonistic and long-winded writing.