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DBL%20Hendrix%20small.png College chemistry, 1983

Derek Lowe The 2002 Model

Dbl%20new%20portrait%20B%26W.png After 10 years of blogging. . .

Derek Lowe, an Arkansan by birth, got his BA from Hendrix College and his PhD in organic chemistry from Duke before spending time in Germany on a Humboldt Fellowship on his post-doc. He's worked for several major pharmaceutical companies since 1989 on drug discovery projects against schizophrenia, Alzheimer's, diabetes, osteoporosis and other diseases. To contact Derek email him directly: derekb.lowe@gmail.com Twitter: Dereklowe

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May 8, 2013

Things I Won't Work With: Dimethylcadmium

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Posted by Derek

Cadmium is bad news. Lead and mercury get all the press, but cadmium is just as foul, even if far fewer people encounter it. Never in my career have I had any occasion to use any, and I like it that way. There was an organocadmium reaction in my textbook when I took sophomore organic chemistry, but it was already becoming obsolete, and good riddance, because this one of those metals that's best avoided for life. It has acute toxic effects, chronic toxic effects, and if there are any effects in between those it probably has them, too.

Fortunately, cadmium is not well absorbed from the gut, and even more fortunately, no one eats it. But breathing it, now that's another matter, and if you're a nonchemist wondering how someone can breath metallic elements, then read on. One rather direct way is if someone is careless enough to floof fine powders of them around you. That's how cadmium's toxicity was discovered in the first place, from miners dealing with the dust. But that's only the start. There's a bottom of the list for breathable cadmium, too, which is quite a thought. The general rule is, if you're looking for the worst organic derivatives of any metal, you should hop right on down to the methyl compounds. That's where the most choking vapors, the brightest flames, and the most panicked shouts and heartfelt curses are to be found. Methyl organometallics tend to be small, reactive, volatile, and ready to party.

Dimethyl cadmium, then, represents the demon plunked in the middle of the lowest circle as far as this element is concerned. I'll say only one thing in its favor: it's not quite as reactive as dimethyl zinc, its cousin one row up in the periodic table. No one ever has to worry about inhaling dimethyl zinc; since it bursts into ravenous flames as soon as it hits the air, the topic just never comes up. Then again, when organozincs burn, they turn into zinc oxide, which is inert enough to be used in cosmetics. But slathering your nose with cadmium oxide is not recommended.

Even though dimethylcadmium does not instantly turn into a wall of flame, it can still liven the place up. If you just leave the liquid standing around, hoping it'll go away, there are two outcomes. If you have a nice wide spill of it, with a lot of surface area, you fool, it'll probably still ignite on its own, giving off plenty of poisonous cadmium oxide smoke. If for some reason it doesn't do that, you will still regret your decision: the compound will react with oxygen anyway and form a crust of dimethyl cadmium peroxide, a poorly characterized compound (go figure) which is a friction-sensitive explosive. I've no idea how you get out of that tight spot; any attempts are likely to suddenly distribute the rest of the dimethylcadmium as a fine mist. Water is not the answer. One old literature report says that "When thrown into water, (dimethylcadmium) sinks to the bottom in large drops, which decompose in a series of sudden explosive jerks, with crackling sounds", and you could not ask for a clearer picture of the devil finding work for idle hands. Or idle heads.

Even without all this excitement, the liquid has an alarmingly high vapor pressure, and that vapor is alarmingly well absorbed on inhalation. a few micrograms (yep, millionths of a gram) of it per cubic meter of air hits the legal limits, and I'd prefer to be surrounded by far less. It's toxic to the lungs, naturally, but since it gets into the blood stream so well, it's also toxic to the liver, and to the kidneys (basically, the organs that are on the front lines when it's time to excrete the stuff), and to the brain and nervous system. Cadmium compounds in general have also been confirmed as carcinogenic, should you survive the initial exposure.

After all this, if you still feel the urge to experience dimethylcadmium - stay out of my lab - you can make this fine compound quite easily from cadmium chloride, which I've no particular urge to handle, either, and methyllithium or methyl Grignard reagent. Purifying it away from the ethereal solvents after that route, though, looks like extremely tedious work, which allows you the rare experience of being bored silly by something that's trying to kill you. It is safe to assume that the compound will swiftly penetrate latex gloves, just like deadly and hideous dimethylmercury, so you'll want to devote some time to thinking about how you'll handle the fruits of your labor.

I'm saddened to report that the chemical literature contains descriptions of dimethylcadmium's smell. Whoever provided these reports was surely exposed to far more of the vapor than common sense would allow, because common sense would tell you to stay about a half mile upwind at all times. At any rate, its odor is variously described as "foul", "unpleasant", "metallic", "disagreeable", and (wait for it) "characteristic", which is an adjective that shows up often in the literature with regard to smells, and almost always makes a person want to punch whoever thought it was useful. We can assume that dimethylcadmium is not easily confused with beaujolais in the blindfolded sniff test, but not much more. So if you're working with organocadmium derivatives and smell something nasty, but nasty in a new, exciting way that you've never quite smelled before, then you can probably assume the worst.

Now, as opposed to some of the compounds on my list, you can find people who've handled dimethylcadmium, or even prepared it, worse luck, although it is an (expensive) article of commerce. As mentioned above, it used to be in all the textbooks as a reliable way to form methyl ketones from acid chlorides, but there are far less evil reagents that can do that for you now. It's still used (on a research scale) to make exotic photosensitive and semiconducting materials, but even those hardy folk would love to find an alternative. No, this compound appears to have no fan club whatsoever. Start one at your own risk.

Comments (53) + TrackBacks (0) | Category: Things I Won't Work With


COMMENTS

1. Hap on May 8, 2013 7:39 AM writes...

1) I think dimethylcadmium was another answer to a test problem in undergrad that the teachers could have used to remove me from the chemistry gene pool had they so desired by asking me to implement my answer.

2) I think The Merck Index (at least the 14th) has a quote very similar to the quote you included about dimethylcadmium's reactivity in water.

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2. PPedroso on May 8, 2013 8:05 AM writes...

I want an autograph of the 1st edition when you put this all in a book. Great read!

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3. Curious Wavefunction on May 8, 2013 8:08 AM writes...

The only time I had anything to do with cadmium was when we were asked to estimate it in sophomore chemistry lab as a sulfide. The whole flask filled up with a beautiful, unforgettable yellow color.

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4. PPedroso on May 8, 2013 8:16 AM writes...

I have a question. What is the use of Cadmium in nature? I mean if it is that toxic and with no known biological roles what is the reason for its appearance in the universe?

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5. Curious Wavefunction on May 8, 2013 8:24 AM writes...

#4: As you know there are a lot of elements in the universe with no known biological roles. But the formation of these elements was an essential part of nucleosynthesis in stars as nuclear reactions produced elements that were successively higher up in the periodic table. So even if these elements are not useful in biology, their formation is required by the laws of physics and they have been around since long before life made its appearance.

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6. Derek Lowe on May 8, 2013 8:38 AM writes...

Yep, Wavefunction's right. Cadmium exists because that number of protons in an atomic nucleus (plus the right number(s) of neutrons) can exist, and all the stable combinations are out there somewhere.

The elements all the way up to iron are made in stars under "normal" conditions - beyond that, it's an uphill process, energetically, so it stalls out. But the heavier ones are made in supernova explosions, which are energetic enough to do all kinds of funky nucleosynthesis.

If you're wearing a wedding band, the gold in it was formed during the incredibly violent explosion of a gigantic star: we don't know of any other way for the heavy elements to be made. (Well, in some cases, there's nuclear decay of even heavier radioactive ones, but *those* had to be made in turn by supernovae. . .)

Life, as you'll see, has nothing to do with any of this, which is a humbling thought.

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7. Fourtytwo on May 8, 2013 8:39 AM writes...

"One rather direct way is if someone is careless enough to floof fine powders of them around you."

I'm always amazed that when people spill chemical powders on their gloved hands or you point out their gloves are a bit dirty then often their first reaction is to start clapping their hands together to remove the powder. Then I start hitting my head off the nearest wall.

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8. BIff on May 8, 2013 8:54 AM writes...

@4 @5 @6 - Lane et al. Nature. 2005. 435:42

Key line: "Here we present the sequence and preliminary characterization of a protein that is a cadmium-containing carbonic anhydrase from the marine diatom Thalassiosira weissflogii."

http://www.nature.com/nature/journal/v435/n7038/full/435042a.html

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9. Anonymous on May 8, 2013 8:57 AM writes...

Derek: So.... Question from a non-chemist again: Just how much of a Bad Thing was accidentally blowing up a 7200mAh NiCd battery due to overcharging back in my youth, if Cadmium can be so nasty?

Fourtytwo: Wouldn't hitting the wall with your head be a bad idea too? I mean, there could be nasty dust on the wall too.....

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10. anonymous on May 8, 2013 9:09 AM writes...

A major application of cadmium, used for over 30 years and very quietly removed from commerce, is as a coating for screws, especially for wood deck work. As a grad student I worked as a framing carpenter and cannot emphasize how common it was for workers to hold a mouthful of screws as one laid in planking. A lot of occupational GI problems can directly be attributed to this use.

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11. BrokenChemist on May 8, 2013 9:24 AM writes...

@9 NiCd batteries contain cadmium as one of the electrode metals, and one of the side products of the battery discharge is cadmium hydroxide. While I doubt that blowing up one would be enough energy to pulverize the cadmium metal in the electrode to make it breathable, it's probably a safe bet that the cadmium hydroxide is not a particularly friendly compound and that would be much more likely to be turned into an aerosol in the explosion.

Nevermind the fact that blowing up a battery is in general a Bad Thing to do.

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12. Doctor Goldie on May 8, 2013 10:36 AM writes...

The mention of dimethylzinc and odours reminded me of this fantastic quote from Edward Frankland, a true pioneer of organometallic chemistry: "After making the reaction for the isolation of methyl by digesting methylic iodide with zinc and after discharging the gases, I cut off the upper part of the tube in order to try the action of water upon the solid residue. On pouring a few drops of water upon the residue, a green-blue flame, several feet long, shot out of the tube, causing great excitement among those present. Professor Bunsen, who had suffered from arsenical poisoning during his research on cacodyl, suggested that the spontaneously inflammable body, which diffused an abominable odor through the laboratory, was that terrible compound, which might have been formed by arsenic present as an impurity in the zinc used in the reaction, and that I might be already irrecoverably poisoned. These forebodings were, however, quelled in a few minutes by an examination of the black stain [which was zinc] left upon porcelain by the flame; nevertheless, I did afterward experience some symptoms of zinc poisoning.”

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13. anonymous on May 8, 2013 10:48 AM writes...

Dumb question. Why use Dimethyl Cadmium instead of cuprate chemistry to make ketones from acid chlorides? Does the cadmium route predate the development of cuprates?

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14. Paul on May 8, 2013 12:36 PM writes...

The elements all the way up to iron are made in stars under "normal" conditions - beyond that, it's an uphill process, energetically, so it stalls out. But the heavier ones are made in supernova explosions, which are energetic enough to do all kinds of funky nucleosynthesis.

Heavy elements are likely made in supernova explosions, but some are also made in large stars by something called the "S-process". Side reactions in these stars produce free neutrons, which get absorbed onto nuclei. When heavy nuclei absorb neutrons, they may become unstable to beta decay, turning the neutron into a proton. This ratchets the elements up the periodic table over periods of thousands of years.

It's called the "S-process" because it's slow (vs. the R-process, for Rapid.) The nuclei have time to decay before absorbing another neutron, on average.

Early stars with very few seed nuclei on which the S process could operate ended up producing large amounts of lead (the end point of the S process, beyond which elements decay back to lead.) Very old so-called "lead stars" (unusually enriched in the element) have been detected.

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15. Derek Lowe on May 8, 2013 1:24 PM writes...

#14 Paul-

Here I am, a chemist and longtime amateur astronomer, and I didn't know the details of that. Thanks!

I see that there's one class of S-process stars that end up going supernova as well, so those must spew all kinds of metallic stuff at their demise.

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16. milkshake on May 8, 2013 3:21 PM writes...

A dimethylcadmium preparation done on massive scale (about 100g of Me2Cd in the flask) was one of my first assignments as undergrad. I made it in situ from MeMgI and CdCl2 (pre-dried with SOCl2) and we used it for transforming PhPCl2 to PhPClMe, all in one pot, according to a Houben-Weyl procedure. The funny thing, we worried more about the atrocious stink of the chlorophosphine product (which is almost as bad as infamous reek of PhPHMe) and de-complexing the Cd leftover crap from the product was pain because Cd sticks to phosphines and one has to use nonaqueous workup with chlorophosphines. I think we used POCl3+pyridine or something else atrocious like that to liberate our product and precipitate Cd away.

I never got to smell or distill our Me2Cd.

(This cadmium chemistry was soon followed by massive mercury preparation, where we had to isolate unstable bis-diazonium salt derived from optically active binaphtyl diamine as bis-iodomercurate and decompose it in carefully dried form, to avoid racemization during Sandmeyer. )

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17. Anonymous on May 8, 2013 4:49 PM writes...

milkshake please write a book before you die

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18. DCRogers on May 8, 2013 6:30 PM writes...

@12

Ah, cacodyl (As2(CH3)4)... first organometallic ever made, as part of the evocatively-named "Cadet's Fuming Liquid".

Bunsen had a great description of the experience:

"The smell of this body produces instantaneous tingling of the hands and feet, and even giddiness and insensibility...It is remarkable that when one is exposed to the smell of these compounds the tongue becomes covered with a black coating, even when no further evil effects are noticeable."

I am assuming the evil effects were only noticed later, as the symptoms of systemic arsenic poisoning manifest.

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19. Rhenium on May 8, 2013 6:42 PM writes...

Milkshake is the bomb, he's done crazier chemistry that one could ever possibly imagine. :)

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20. Rhodium on May 8, 2013 6:44 PM writes...

After reading this, I had a radiation safety committee meeting, where I realized that no matter how bad a molecule is, we can make it worse with a little radioactivity. So, if dimethyl cadmium is something you can work with, how about the tritiated derivative, or the C-14 version, or even one of the many cadmium isotopes. Has anyone made dioxygen difluoride with F-18 (I hope not)? About the only thing I can think of that this trick will not work with is ozone or some of the nitrogen oxides.

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21. Schlake on May 8, 2013 7:14 PM writes...

Years ago I lent some D&D dice to a guy named Evan. He was a chemist; the scary kind who liked to make things he shouldn't. One game we often played at his house was to rub the kitchen table with a wire and then flame test it to find out what color it was that day. When he returned the dice, in a bucket, I put them on the gaming table for public use. We joked for years, YEARS, about them, telling new gamers never to put the dice in their mouth, or touch their face, and to wash their hands after they had touched them, simply because Evan had once borrowed them. It was a funny joke.

In all those years no one every really looked at the bucket he had returned the dice in. One day, another chemist, picked the bucket up, and looked at, and in a loud and startled voice said "WOODS METAL?!"

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22. gippgig on May 8, 2013 8:00 PM writes...

So... what does dimethylcadmium look like?

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23. Anonymous BMS Researcher on May 8, 2013 8:23 PM writes...

In some countries, cadmium yellow pigment is currently banned from any plastics that might end up being used to make toys for children.

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24. Anonymous BMS Researcher on May 8, 2013 8:28 PM writes...

@18 DCRogers

Amazingly enough, Bunsen lived till 1899, he was 88 years old when he died.

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25. Hap on May 8, 2013 9:16 PM writes...

Alas, Milkshake's story gets even better...

http://pipeline.corante.com/archives/2007/02/01/how_not_to_do_it_ruining_stuff.php#183447

22: Apparently (Merck Index 14, #3266), Me2Cd is a liquid (doesn't say what color), bp 105C. I'm guessing clear, but it doesn't say, and I don't know.

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26. milkshake on May 8, 2013 10:03 PM writes...

Bunsen had no stereovision because he blinded himself in one eye in explosion, during one attempted Me2AsCN preparation. The some compound later nearly fatally poisoned him, twice, but he recovered from semi-unconscious state and went back to work. Since they did not have fume hoods in these days and he realized the very high acute toxicity of this volatile compound posed a little problem, he resumed the research project later by doing experiments while inhaling and exhaling through a long glass pipe that was stuck through a window...

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27. free on May 8, 2013 11:57 PM writes...

Familiar as you are with the grave toxicity of many metals, and their multitude of detrimental effects on nearly every biologic system and activity, and given your familiarity with disease research, what is your opinion on why more attention is not given to these class of toxins and other environmental toxins, for that matter, in the Etiology of so many "mystery" diseases (i.e. ALS, chronic fatigue, lupus, Alzheimer's, autism....)?

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28. Jon on May 9, 2013 12:41 AM writes...

@ #10 Anon: Just as a sidebar, cadmium-plated hardware was (for awhile) popular in automotive fasteners as well, where it's now a nasty little contaminant in car recycling.

J.

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29. Carl 'SAI' Mitchell on May 9, 2013 3:31 AM writes...

The most common use of cadmium for a very long time was in yellow pigment. My mother is an artist, she has cadmium yellow and red (sulfide and selenide, respectively) oil paints (though she's quite careful with them and doesn't use them often.)

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30. Falanx on May 9, 2013 5:50 AM writes...

Further to previous uses for cadmium;

Cadmium metal is still used as a plating on a limited number of aerospace parts as the argument goes its unique tribological properties are not matched by any other element or plated alloy. The veracity of this argument is open to debate, but when FAA, EASA and CAA safety mandates require a certain level of performance, they're loath to certify new technologies until they really aren't new anymore.

The EU also mandates cadmium pigments for safety-critical signage. No other red (with the exception of lead chromate molybdate) or yellow (with the exception of lead sulphate chromate) matches the level of UV permanence.

With regard to those external-use woodscrews from way back, they were cadmium plated, then chromate conversion caoted, a double whammy of carcinogenic toxins. However, the chromate conversion coating in cadmium has a solubility product of ten to the fourty-something in saliva, and is self-healing, so I wouldn't worry too much.

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31. Jordan on May 9, 2013 9:48 AM writes...

Cadmium acetate is a good catalyst for making oxazolines out of amino alcohols and nitriles. Did a bit of that in grad school.

Also note that much of the "quantum dot" world works with CdS and CdSe or sometimes the Pb equivalents.

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32. Bruce Hamiton on May 9, 2013 12:14 PM writes...

Cadmium and selenium ceramic glazes give the brightest and most durable colors. There are now limits for extraction ability when used on cooking and food ware, but they are still used for art ware. Cadmium and lead salts were used in early plastics before being banned due to high levels of leaching in contact with foods in the 1960s and 1970s.

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33. lelldar on May 9, 2013 1:58 PM writes...

Dimethylcadmium can be used in growrth of CdS/CdSe/CdTe thin films with gas phase techniques (at least atomic layer deposition). Most likely other nanomaterials from Cd-chalcogenides too, which are important materials in e.g. solar cell applications and nanodots as Jordan pointed out.

For liquid phase techniques there must be other alternatives though in materials chemistry but in gas phase the toxicity isn't too bad and there are quite many toxic (and very many pyrophoric and otherwise nasty) chemicals used. Of course the exhaust gases have to be treated carefully (at least when making CdTe, H2Te is nasty too... LC50 is 2 ppm/1h).

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34. Anonymous on May 9, 2013 5:45 PM writes...

Dimethyl cadmium is also one of the references for Cd-113 nmr, according to Bruker's nmr periodic table. Neat dimethyl mercury is the reference for Hg-199 nmr. I'm assuming this is done for historical reasons, but suppose the tube broke in the magnet, fell into the probe and shattered. Or broke anywhere for that matter....

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35. eyesoars on May 9, 2013 10:56 PM writes...

In Kelly Johnson's memoir, IIRC, he mentioned a few issues with the titanium sheets used to fabricate the SR-71. One was that things built during the summer failed their tests. It turned out they used city water to wash the fresh sheets, which had trace amounts of a mercuric compound as an algicide that caused the sheets to decompose oxidatively. After this discovery, they switched to deionized water for washing.

The other was that engineers would mark the sheets with pencils for bends, usually mechanical pencils, and the sheets would later fail along the folds. This was due to cadmium plating of the pencils, which had a similar effect, again causing the titanium scratched by a mechanical pencil to oxidize to failure.

This led to the banning of all plated tools from the skunk works.

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36. newnickname on May 10, 2013 6:40 AM writes...

Following up on refs to Bunsen and other heroes of 19th Century chemistry, I quote from Max Gergel: "[...] he would let me make the compound which he really wanted, alpha-bromo-beta-methoxypropionaldehyde dimethylacetal, a really long name for a chemical. I told him that, as I
recalled, this had been produced by the celebrated German sugar chemist, Emil Fisher, sixty years ago. I recalled that Fisher advised (in German) that one should operate "im lustige wind" which translates to "in a strong wind". It is to be presumed that there were no good bench hoods in those days. There was no good hood at Columbia Organic Chemicals either. [...]"

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37. Joe on May 10, 2013 11:24 AM writes...

I seem to recall that cadmium was used in teh plating of the grated shelves in refrigerators. This led to a problem when people used the grates from defunct refrigerators as impromptu racks for bar-be-que.

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38. Derek Lowe on May 10, 2013 12:44 PM writes...

#37 Joe

Here you go!

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1929634/

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39. PedroDaGr8 on May 11, 2013 1:29 PM writes...

As someone who has made grams of CdSe/CdS/ZnS quantum dots,I am very very familiar with cadmium. It's interesting to read a lot of the literature on QD from the 90s because they almost invariably used Me2Cd. IIRC it wasn't until somewhere around the turn of the millenium when Xiaogang Peng at Univ. of Arkansas showed a method for making QDot's which used TOPO and CdO instead of the much more joyful Me2Cd. That being said, in the above synthesis it puts several great compounds: CdO powder, cadmium salts of steric, oleic or myristic acid, diethyl zinc, and some really fun volatile sulfur compounds; my boss spilled ~3mL in the fume hood (which are certified every 3 months for proper air flow) and evacuated the whole building because they thought it was a gas leak.

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40. Baltic on May 15, 2013 7:44 AM writes...

Doing high-temp reactions in Wood's metal bath is as close as I've been to cadmium, apart from analytic chem lab assignments in university (CdS is one of the prettiest compounds I've seen there). I don't think the metal bath produced enough cadmium vapour to be of concern, and it was always placed as far inside fume hood as possible - this was done due to the fact that reaction I was running was a dehydrogenation/aromatization which used elemental sulfur, and therefore produced more-than-pleasant amounts of hydrogen sulfide.

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41. Sili on May 20, 2013 7:21 PM writes...

Amazingly enough, Bunsen lived till 1899, he was 88 years old when he died.
Presumably no infectious agent could survive inside him. Permalink to Comment

42. Anonymous on May 24, 2013 11:11 AM writes...

Uses of Cd
I remember a conference where a speaker argued that Cd could potentially be used in gun barrels as a lubricant for the ammo. It turns liquid under the high pressure occuring during shooting, yielding a formidable, temporary tribofilm reducing wear of the barrel. Especially in the really big ones, like artillery.
I guess if you shoot those things you don't really care about health but rather the exact opposite.

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43. Ignatios Souvatzis on May 27, 2013 3:15 AM writes...

Re: [20] radioactive version of FOOF ?

A Tall Tale by Charles Stross is a (fictional) story about combining FOOF with (I think, given the details, fictional) Dimethyl-(radiocative Mercury) as an extra exergonic rocket propellant.

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44. A PhD student on June 3, 2013 12:24 PM writes...

I see cadmium and raise you thallium for toxicity. from personal experience it can have horrific effects on the human body.

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45. Ed on June 13, 2013 6:00 PM writes...

When I worked as a gas turbine test engineer (until Dr Lowe's blog I thought using boiling wide cut in a test was really bad...), we never use cadmium plated fasteners, as Cd caused embrittlement.

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46. Anonymous on June 21, 2013 11:03 AM writes...

I don't read the news. I read this blog.

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47. WizardOfBoz on July 3, 2013 8:02 AM writes...

Cadmium is an excellent, cheap protective plating for metal. It's toxicity makes its use unwise for almost any practical application.

Beryllium is another bad actor. Look up beryllosis. Machinists working with the metal (which has some cool, useful properties) would inhale dust from grinding beryllium and would get the disease later in life.

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48. earfluffy on July 13, 2013 5:54 PM writes...

Strangely the only thing I could think about while reading this was: 'My god, what could Lex Luthor do with this stuff?'

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49. TJ on August 11, 2013 4:34 PM writes...

Derek,

Sometimes I think that writing about things that scare the sh*t out of you brings out the most creative and colorful side of your writing. I seriously think, as someone else here suggested, that you should put together a small book or booklet of some kind that collects the entire Things I Won't Work With series. Even if it were just like a small booklet you put together yourself and made available online. The series is entertaining for non-chemists as well and communicates something about the hazards which synthetic chemists must be cognizant of.

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50. Hasufin on August 15, 2013 11:05 AM writes...

When I worked at a paint store, one of the pigments we used was "Cadmium yellow". As far as I know, that pigment is still in use. However, I do not know that actual chemistry of that pigment - no idea what compound it has in it, or even if it's simply a name retained well after the formulation has changed.

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51. TessC on August 17, 2013 3:40 PM writes...

OH, how I wish you wrote textbooks! I barely made it through high school chemistry, but I read through this entire category on your blog. I laughed out loud at least three times an entry. Even more, I understood the science and gained info that will help me understand less diverting chemical reports. Thank you! And I'm serious about the text book suggestion. Many many classes of students would give you undying gratitude for saving them from acute boredom.

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52. Ken on January 11, 2014 10:17 PM writes...

Man, those guys are tame. They went for dimethyl cadmium, but didn't take a trip down through the rare earth metals? For shame. They should give dimethyl plutonium a run through the lab.

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53. Autolykos on April 8, 2014 7:17 AM writes...

@Ignatios Souvatzis:
Actually, Dimethylmercury was once thrown around as an idea to increase the thrust of rocket engines at the start.

In flight, you want your exhaust as light as possible to make the individual molecules faster at the same temperature, to maximize specific impulse.
But at the start you couldn't care less about the specific impulse of your fuel (you won't carry it for long anyway) but want to maximize thrust instead. And for this, heavy exhaust is generally what you want.
Now, optimizing both specific impulse and thrust with the same engine is hard, and using two engines is a lot of dead weight, so one idea was to put a heavy additive into the fuel used at the start, and someone (it should be illegal to hire morons for space programs...) thought it might be smart to use Dimethylmercury (because, what could possibly go wrong?).
One can assume that the idea was buried after that someone tried to order a few tons of the stuff and received a less than polite answer from the chemical supplier of his choice...

But making the mercury radioactive (the heavier the isotope, the better...) and using FOOF as oxidizer (rocket fuel can never be too energetic or too hypergolic, right?) is just gratuitous. I sure hope that story is fictional.

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