Category Archives: Chemistry Blogs

BLEVE- Boiling Liquid Expanding Vapor Explosion

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There is kind of fire behaviour called a BLEVE– Boiling Liquid Expanding Vapor Explosion.  A BLEVE is what happens, for instance, when a closed container of flammable liquid is exposed to strong heating.  It can be caused by an external source, like a pool of burning liquid around the container, or it can result from a runaway reaction within a drum, cylinder, or tank.  The internal pressure builds up more rapidly than it can be vented and the containment fails, often explosively. It is interesting to note from the above link that boiling action of the liquid phase in the container absorbs energy and has a cooling effect, but there may come a point where the vapor pressure rise above the liquid exceeds the capacity of the relief discharge capacity and the vessel fails, discharging liquid and vapor across the burn zone.  At minimum, discharge and ignition will lead to a large flare, or if conditions are right, an actual detonation of the fuel/air mix could happen over a relatively large space.

These things often begin with some kind of tank or tanker accident (link updated 6/10/16) resulting in a discharge and ignition of flammable liquid.  As responders arrive they find a burning pool under or next to the tank(er).  Naturally, firemen and bystanders try to help those who may be hurt. As the minutes tick away and the fire becomes more aggressive and the tank gets hotter, the firefighters get their equipment in place and attempt to cool the tanker and suppress the fire.  Suddenly the tank fails and there is a prompt bulk discharge of liquid and vapor yielding a large fireball which may include an explosive shock, flying metal debris and a dangerous heat pulse.  It is at this point that the surviving bystanders and responders see the error of their ways.

Containers of flammable liquids rarely explode in a symmetric fashion so the container or its fragments are likely to be sent flying at high velocity, possibly spewing flammable material as it moves.  Even a relatively small volume of flammable liquid dispersed explosively can fill a large surrounding space with a fireball.

All chemical plants have their protocols for emergency response.  It is important for those in charge to recognize an incipient BLEVE and respond accordingly.  But even academic chemists should familiarize themselves with the phenomenon.  A fire in the lab engulfing closed containers of flammable solvents is extremely dangerous and very quickly firefighting may become your last earthly act, especially without personal protective equipment.  It is easy to under estimate the violence of these things.

Every lab person needs to look inward and decide what their personal limit is for dropping the fire extinguisher and running for the exit.  In my sophomore organic labs, the seed I planted in the students mind was this: The main purpose of a fire extinguisher was to fight your way to an exit.

Sacred Cows Make the Best Hamburgers

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I suppose I have lost more frequently than I have won in my lifelong avocation of taking on sacred cows in the battle of wits.  But, truly, sacred cows make the very best hamburgers.  Pass the A1 …

Some new blogs have been given a place of honor in the blogroll.  Good writing and laser sharp insight are the keys to this ascendency. If the dear reader is conservative and prone to weeping or bed wetting, it is probably best to click along at this point.  

There is a hilarious post over at Lawyers, Guns, and Money called Birthday Girl.  Side note: A lawyer friend is fond of saying “Lawyers, guns, and money- pick any two”.  

And then, what can I say about Jesus’ General?  Read General JC’s letter to the Secret Service re Cheryl Crow.  If you are keen on some serious in-your-face-atheism, check out Hellbound Allee. Then there is one of the best Christian evangelical lampoons ever, Landover Baptist. 

The Huffington Post is a recent find and is a treasure trove of political blogging at its finest- well, if you are a liberal.  Read the open letter to Rudy Giuliani by my fellow Coloradoan, Gary Hart. 

Then there is the Proceedings of the Athanasius Kircher Society.  The post on the Do-Nothing Machine is particularly amusing.  The reader may recall Th’ Gaussing’s previous post on the Katzenklavier. 

Finally, The Agonist has some interesting insights into politics and is well written. I also like Goosing the Antithesis for its skeptical stand against belief in the supernatural.

Mixing and Unmixing

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Today was take-your-kid-to-work-day.  In honor of this we put on a chemistry show in one of the labs.  Burned some Mg ribbon, shrunk some balloons in LN2, blew up some balloons with dry ice, reduced iodine with ascorbic acid, and we unmixed some NaCl and carbon black. 

One of the barriers to teaching chemistry is a level of physical abstraction that is hard to get around.  It is hard to get around trivial explanations when the audience is not ready to discuss electrons.  Many of the really insightful concepts in chemistry are inherently abstract and age inappropriate for the younger crowd, so to compensate, chemistry demonstrations are often heavy in the whizbang components.  That’s fine.  It should be fun and visually appealing, especially for K-6. 

I like to do mixing and unmixing because it demonstrates something about materials handling.  It also represents an activity that occupies much of our time.  Separation science is not commonly called “unmixing”, but for chemistry demonstrations it causes kids to ponder the problem for a bit.  They all have experience in mixing things- we talk about that.  Then I ask the question “What if I asked you to unmix that KoolAid”?  A few of the more worldly ones might suggest boiling off the water.  But most kids seem to be stumped- they will admit that they would have never considered the possibility of unmixing. 

So we dissolve some NaCl in water and make a solution.  The use of a magnetic stirrer and stirbar makes way for a minor diversion with magnets and iron filings. Then we blend in a bit of carbon black. Using a Buchner Filter, filter paper, and Celite, we do the vacuum filtration, showing the remains of the carbon in the Celite.  The filtrate is then treated with some “Anti-Solvent” like acetone and the salt comes crashing out. 

Yeah, I know. It is pretty tame.  But it can be done cheaply in 45 minutes and the kids can see their parents actually doing something. 

Happy 100th Birthday Albert Hoffmann!!

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Albert Hoffmann, the discoverer of LSD, turned 100 years old this year on Juanary 11th.  Happy Birthday, Albert!  Scienceblogs.com relates the story of Hoffmann’s first deliberate LSD trip on April 19th, 1943.  You might recall that Hoffmann was the Sandoz chemist who stumbled upon the psychotropic activity of lysergic acid diethylamide.  

Just this last week, the medical journal The Lancet called for an end to the “demonization” of psychedelic drugs, according to Guardian Unlimited.  The motivation behind the editorial in the Lancet was to urge a loosening of taboo’s connected with the use of psychedelic compounds.  The widespread criminalization of psychedelics has made research with these interesting molecules quite problematic. 

Perhaps the day will come when such materials are decriminalized and it will be possible to visit a psychedelic spa where one could go to have a safe dosage administered by qualified staff.  But it wouldn’t be all fun and games, though.  While the euphoric experience can be prolonged and profoundly vivid, there is a dark side.  An account of the experience of the psychiatrist Werner Stoll is described in Chapter 4 of Hoffmanns book “LSD. My Problem Child”.

Hoffmann and Sandoz would watch their discovery move from a psychiatric adjunct to a full fledged inebriant adopted by a counter culture movement.  In his book, Hoffmann laments-

    This joy at having fathered LSD was tarnished after more than ten years of uninterrupted scientific research and medicinal use when LSD was swept up in the huge wave of an inebriant mania that began to spread over the Western world, above all the United States, at the end of the 1950s. It was strange how rapidly LSD adopted its new role as inebriant and, for a time, became the number-one inebriating drug, at least as far as publicity was concerned. The more its use as an inebriant was disseminated, bringing an upsurge in the number of untoward incidents caused by careless, medically unsupervised use, the more LSD became a problem child for me and for the Sandoz firm.

    It was obvious that a substance with such fantastic effects on mental perception and on the experience of the outer and inner world would also arouse interest outside medical science, but I had not expected that LSD, with its unfathomably uncanny, profound effects, so unlike the character of a recreational drug, would ever find worldwide use as an inebriant. I had expected curiosity and interest on the part of artists outside of medicine-performers, painters, and writers-but not among people in general. After the scientific publications around the turn of the century on mescaline-which, as already mentioned, evokes psychic effects quite like those of LSD-the use of this compound remained confined to medicine and to experiments within artistic and literary circles. I had expected the same fate for LSD. And indeed, the first non-medicinal self-experiments with LSD were carried out by writers, painters, musicians, and other intellectuals.

Today, psychedelic substances are considered to be drugs of abuse and their use will lead to a long stay at the Gray Bar Hotel. Our Puritanical heritage seems everlasting. But rather than wallow in pity for my unenlightened brothers and sisters, I look forward to a brighter future where one could sit in a licensed psychotropic suite and explore the deepest recesses of consciousness brought out in full non-linear display, say, while listening to music. Everybody associates acid rock with LSD. That’s too easy. I’ve often wondered what it’d be like to listen to Leon Redbone in an altered state of consciousness.  Kinda curious about what a baritone sax does to a brain on acid.  Or David Bowie- Major Tom.  I’m showing my age. 

Along Came ChemSpider

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There is a new resource out there called ChemSpider.  In the few searches I’ve had a chance to do, it seems to be pretty efficient at separating a lot of the wheat from the chaff that you’d get just using Google.  It would be interesting to hear what others think of it.  According to the informative FAQ page, ChemSpider is a highly specialized chemistry search engine.  And, did I mention it’s free?  Yeah baby.

To begin you enter a name, CASRN, tradename, synonym or SMILES. This generates a report of hits. Click on an ID number or a structure and another page brings up hotlinks to various resources on the web. Click on the Data Sources link and another page will come up with a variety of data sources and their unique external ID numbers. Click on the molecular formula link and it pops off a Google search of the formula.

Obviously, this isn’t the same as a SciFinder search- you don’t get access to journal downloads and article bibliographies.  It connects you to a variety of public access sites that appear to be data repositories and collections of commercial suppliers.  But it is a real improvement over a raw Google search.  You don’t get the rats nest of links to publishers (i.e., Wiley, Elsevier, etc), expired colloquium notices, or literature citations from curriculum vitae on faculty websites.  

It will convert names to structures and, using ACD/Labs software, generate calculated physical properties.  I would be hesitant to enter the identities of confidential materials just yet. I do not know if they compile entries into a database or not.  I’m not convinced that I would enter a sensitive confidential material on it until I had a chat with an attorney about the question of disclosure.

All in all, it seems to be a useful tool for web searches.  I have only scratched the surface of what this thing will do.  Give it a try and see what you think.

First Class Tickets to Stockholm

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The buzz has begun for the 2007 Nobel Prize in Chemistry.  Over at ChemBark a list of fields and potential awardees is presented.  Odds are offered.  It is interesting to ponder.  In case you were wondering, the identities of the awards committee for 2007 is actually published.

When the committee calls for my opinion, I’ll have to set ’em straight.  First I’ll scold a bit about the snub of some early workers in asymmetic synthesis and how they were overlooked in 2001. People like Henri Kagan for C2 symmetric ligands among other things and Kurt Mislow for basic contributions to stereochemistry.  The guys who won in 2001 were deserving, but the omission of Kagan and Mislow is a shame.

I would like to see some organometallikkers like Suzuki, Heck, and Sonogashira get the recognition for their contributions to coupling chemistry, but I’m not sure it is a Nobel Prize body work.  I would prefer to see Bergman , Whitesides , or Harry Gray get the trip to Sweden for their fundamental contributions to organometallic and bioinorganic mechanism work. 

There is my free advice to the commitee.

Chemical Plant Production Managers

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I have known a few plant production managers at several facilities in my career and they seem to share particular attributes. No doubt they fall into a particular Myers-Briggs type.  I can say without a doubt that I am personally disqualified from such activity because I tend to be more of the absentminded professor type.   It takes a certain breed of cat to manage any kind of production facility.  Indeed, your average construction site superintendant is probably better suited to manage a chemical plant than is a chemist. 

Well, OK. That was a bit harsh.  Many chemists could do it if they had to. But if you owned a chemical company and were looking for a new plant manager, you’d probably find that the pool of candidates didn’t include many chemists. There, that is more polite.  Chemists are often tweakers by nature and a chemical plant is not a place for experiments. Plant managers live by the production schedule. They are both masters of and slaves to this schedule.  Their whole careers are about the coordination of material flows- the arrival of raw materials, processing, and the logistics of shipping.

A chemical plant is a big machine through which flows a large stream of money.  Money flows in one side of this machine and out the other side.  Jets of cash flow outward to payroll and raw material vendors. The production manager never forgets that the inflowing stream must always be bigger than the outflowing stream.  Customers insist on just-in-time delivery of products, but they also want 60 days net with a lot of other strings.  The relationship between the controller and the plant manager may be chronically strained.

People who run production plants are really engineers, irrespective of whether or not they hold a diploma in engineering.  Scientists find the thread between cause and effect.  Engineers take that thread and figure out how to use it for fun and profit. Sure, some scientists have engineering sense and some engineers have scientific sense.  But a plant manager is all about running the plant at full speed. When they make tweaks, it is usually on the engineering side.  Usually they are loath to alter chemistry.

In the Navy they have a saying- Fight the Ship.  Use every part of the boat to your advantage.  Slap ’em with the rudder if it comes to that.  A good production manager is crafty, thrifty, and when needed, a brutal task master.  He knows his crew and can and will push them to the edge when needed. 

A really smart plant manager will find and keep the best maintenance people he/she can find.  In fact, a savvy plant manager will always vote to throw a chemist overboard rather than let a maintenance person go.  One of the least acknowledged groups at a chemical plant is the maintenance crew.  To keep the plant up and running you need the skill sets of plumbers, welders, pipefitters, machinists, electricians, iron workers, carpenters, tinners, and a bunch of general handymen and gofers.  Usually you hire people with multiple skill sets.

The best plant managers are steely-eyed SOB’s who speak softly and command respect and maybe a little fear. A plant manager must be able to work effectively with arrogant executives, stubborn accountants, egghead scientists, angry admin staff, defensive production people, and sly construction contractors.  The people skills are as important as the technical skills.

If I were going to hire people for key management positions in a plant, I would hire people from the nuclear Navy. As a group, they have already been screened for many attributes useful to a chemical plant. They tend to be high achievers, have good quantitative skills, have been highly trained for work in hazardous environments, and they understand the importance of following protocol.

GD vs ICP Mass Spec

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I wonder if there are any mass spec jockeys out there who can comment on the relative accuracy of Glow Discharge Mass Spec (GDMS) with ICP Mass Spec (ICPMS)  at the ppm level?  In other words, if one has data taken from each and compares them side by side, which should one side with? I have results from both analyses on a metal oxide and I’m puzzled as to which I should stand behind. 

If you have one clock, you know what time it is. If you have two, you’re never sure.

One lab breathlessly proclaims that GDMS is linear over 9 orders of magnitude, but is subject to 20 to 30 % error owing to a lack of a valid standard (??!@#?). The same fellow says that ICPMS is accurate to 5 % at 100 ppm, but the error is considerably higher at 1 ppm. Good gravy.

No doubt, the answer will contain the words “it depends”.  But I wonder what the issues are. 

Plasma Songs From Space

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The radio telescope project has begun. Today I ordered a 20 MHz receiver from Radio Jove.  While we wait for that to arrive we have to source an 8 channel Analog to Digital Converter (ADC) for the data feed into RadioSky-Pipe.  RadioSky has run out of ADC’s, but they recommend Kitsrus out of Hawii.  

We have three surplus computers I bought from work.  Have to pick one and get an operating system (Windows 2000, probably, though Linux is a possibility), a monitor, and a keyboard. 

The biggest issue is the recommended dipole antenna. The kit specifies an East/West 23′ 3″ ft dipole with a 32 ft footprint, is ca 10 ft high, and uses guy wires to stabilize it. Sounds like a trip hazard and a target for vandalism to me.  In that vein, I have been looking at alternative antenna configurations. The folks at Radio Jove are reticent to recommend one, presumably because it is a step away from simplicity for classroom use.  That’s fine. I’m an experimentalist.

One problem with moving away from the dipole antenna design is the unwieldy half-wavelength dimensions. While the dipole eats up real estate, it is structurally simple.  One interesting design is the Moxon antenna.  This antenna uses a bent driven element with a bent reflector element.  Most people use it with the elements in the horizontal plane, thus picking up horizontally polarized signals.  While this makes sense for communications, I’m guessing that the 20 MHz signals from the sun and Jupiter are probably not significantly polarized.  

The Moxon is significantly more directional than a dipole with a front to back ratio 15 to 20 db.  This means that it must be pointed at the radio source for maximum gain.  But its directionality also confers some rejection of terrestrial signals from other directions. From what I can tell, the gain from this design with its reflector element is on the order of 5 db.  This is higher than a dipole but lower than a multi-element Yagi.

We’ll get some baseline experience with the recommended antenna and then begin to look at other configurations.

In my view, one can never know too much about electronics.  This site has some interesting circuit animations.  Cheers!

The Zen of Hazardous Materials

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My first experience with truly hazardous materials was in 1981.  It was a sophomore organic lab and we were making sulfanilamide.  Using chlorosulfonic acid, we attached a ClSO2 group in the para position of acetanilide.  Pedagogically, it was a very rich experience because it validated the idea of O,P-directors, protecting groups, medicinal chemistry, and offered real experience in the handling of hazardous materials.  And, at least as corrosive materials go, they don’t get much more obnoxious than chlorosulfonic acid.

The preparation of sulfanilamide was an excellent lab experience because it brought home some fundamental truths about nature.  Namely, that physical and chemical properties of matter can be “tuned” and tweaked by people to give a desired outcome.  For students, this lab experience connects the inorganic, inanimate world of the periodic table to something closer and more personal.  It gets to the very nanomachinery of life itself.  It is a glimse of how drugs work. It gets right to the pointy end of the stick- Drugs are about selective toxicity. 

Once you have taken the time to gain some understanding of how drugs work at the molecular level, you are forever changed.  One begins to realize that biochemical “mistakes” can happen naturally and are part of the game.  Suddenly, the world is full of rogue “isosteres” and “pharmacophores“.  You can no longer accept blithe generalizations about toxicity and chemical hazards.  There is truth in the First Law of Toxicology- Dose makes the poison.  Your working definition of toxicity takes on new forms, like the notion of endocrine disrupters. 

As time goes on and my view of the natural world becomes increasingly molecular in scope, I find that my working definition of what constitutes “hazardous” has skewed a bit as well. Hazardous does not automatically equal “bad”. The modern material world is now a swirl of substances synthetic and substances natural.  Industry has given us dioxin and nature has given us aflatoxin.  But at worst nature is indifferent; human activity can be negligent or even malevolent. 

A mature view of hazardous materials must simultaneously accomodate physical/chemical reality with certain norms of conduct, with prompt and delayed biological effects of hazardous materials, and with consequences to the biosphere.  In truth, modern society must use hazardous materials to produce goods and services vital for healthy living.  But we chemists must find ways to limit the number of moles of hazardous waste we generate. Especially the persistant substances- metal salts, halogenated hydrocarbons, etc.

Synthetic chemistry relies on reactive materials in order to do bond making and bond breaking.  There really is no getting around the need for reactive materials. But we can find ways to generate reactive materials in situ.  Reactive intermediates are generated in a catalytic cycle and used on the spot.  More pervasive use of catalysis could be a contributor to lower generation of haz waste or a greener chemistry.  This is just a corollary to Trost’s Atom Efficiency concept.

Hazardous materials have a utility that is similar to a knife.  A knife is a tool that does a very useful thing- it cuts. Every single time you pick it up you have to be wary of the edge and the point.  It is a persistant hazard.  But we continue to use it because of it’s utility.  In a way, chemicals are the just like that.