Category Archives: Chemistry

ReactIR. Infrared spectroscopy revives in the age of NMR.

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We have a brand new Mettler-Toledo ReactIR 15 sitting in my lab. It is rather simple to use- just dip the probe in your reaction mixture. It needs a little LN2 to chill the detector. The software is reasonable, bearing some resemblance to iControl of the RC1 sitting a few meters away.

The instrument is used to follow the progress of a reaction by monitoring the growth or extinction of IR absorptions. What is interesting for the user is that it is not necessary to identify any of the peaks in the course of an experiment. The software can integrate absorptions and plot their change over time. The fingerprint region of the IR spectrum is put to good use in that it is a fruitful region for numerous absorptions to appear.

The thing is still new to us, so we’re early in the learning curve. The probe in use has a wave number range from 2500 to  about 650 reciprocal centimeters. It is possible to detect up to 3000 wave numbers with a different probe. The probe is connected to the interferometer by a fibre optic cable comprised of a silver bromide optical pathway.

The thing is the size of a coffee maker and costs as much as a used helicopter. The ATR probe tip is small enough to be immersed in experiments at the scale of a scintillation vial or a 5 liter flask.

What it brings to the table is the ability to follow the progress of reactions in real time for process optimization. Pulling samples and trudging over to the NMR for in-process checks is tiresome and time consuming.

One limitation is the electrical classification. As with other electrical devices you have pay attention to the NFPA classification of the space it sits in. The ReactIR 15 is class 1, but not division 1. If the instrument must be used in this space, there are ways to fashion an enclosure to get around this, according to Mettler. Have a look at your computer as well. If your computer throws sparks and coal cinders, you may want to keep it away from that pool of pet ether on the floor.

Blogopithocene Man Smelts Tin. Meh.

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The problem of the origin of Cu:Sn bronze has intrigued historians for many years. Bronze artifacts have been dated to 5000 BCE on the Iranian Plateau.  It is thought that the earliest bronzes were arsenical in nature. The presence of arsenic in copper metal or copper ore is not uncommon.

Copper can be found as the native metal but the smelting of copper ore appears to date back to ca 5000 BCE in southeastern Europe in what is now Serbia.

Most commonly today, the word bronze refers to a range of copper alloys comprising various proportions of copper (major, e.g., 88 %) and tin (minor, e.g., 12 %).  As the tin content increases, the resulting alloy changes properties and may have a unique purpose and name. For instance, a ratio of ca 2:1 :: Cu:Sn is called speculum and was prized for it’s ability to take a high polish for mirror applications.

Further down the composition range are varieties of pewter which are alloys comprised substantially of tin and a few percent of copper and antimony for hardening.  Many specalized compositions of pewter have been developed. Britanium or Britannia metal is an alloy comprised of 93 %Sn, 5 % Sb, and 2 % Cu. This alloy serves as the base metal Oscar Award Statue upon which gold is plated.  Pewters composed of Sn:Pb were commonly used as well.

Tin is not found in the metallic state in nature. It is oxophilic and occurs primarily as the tin (IV) oxide mineral, cassiterite. Tin ore was mined in Cornwall, England, for instance, for many centuries before recorded history.  Today, most of the worlds tin comes from Asia, South America, and Australia.

The jump to “engineered” bronze was a step change that involved the reduction of a tin mineral either in situ with copper or in isolation to produce discrete tin. It is thought that polymetallic copper ores were smelted, producing Cu:Sn bronze directly. Eventually, tin ore was identified as a source of smeltable metallic tin.  Why anyone would think to apply reduction conditions to a mineral as seemingly featureless and uninteresting as cassiterite is an intriguing question.

Below is a photo of the result of my first attempt at smelting a cassiterite simulant (SnO2, Aldrich). The SnO2 was treated with carbon black at 900 C for 4 hours in a covered porcelain crucible in a muffle furnace.  After a  failed attempt with a large excess of carbon, the ratio was reversed and heated for a longer period.  For the illustrated sample, the mass ratio of SnO2 to carbon black was ~2:1. All of the carbon black was consumed, leaving a white mass of needles on the granular solids.  Using a USB microscope I searched for evidence of reduction to the metallic state and found numerous examples of sub-millimeter sized pieces of metal.  The yield of metallic tin is estimated at < 1 %.

The purpose of this exercise (for me) is to try gain a better sense of what problems people might have faced smelting tin in antiquity.  Using basic principles, I strongly heated the SnO2 under reducing conditions until the carbon was consumed.  What I did not expect was the large amount of white crystalline material produced. It’s composition is as yet unknown to me.

Next I will make some charcoal or even wood shavings as a reductant for authenticity sake. Who knows, maybe some carbon monoxide generation might be helpful. The muffle furnace does not simulate a reverberatory furnace very well. It could be that gases from a reducing flame are important.

Smelting of Cassiterite Simulant

Mining Asteroids

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The founders of the Silicon Valley startup, Planetary Resources, have announced plans for mining asteroids for valuable metals. Peter Diamandis, Eric Anderson and investors including director James Cameron and Google CEO Larry Page are behind this venture.

I’m trying to be positive here. Perhaps these fellows should visit some earthly mines and see what it takes to break actual rock and extract the value from it.

Earth bound ore bodies near the surface are commonly the result of concentration by hydrothermal flows. In the absence of water-based geothermal concentration processes, or recrystallization of PGM’s in magma chambers, the reality of economically viable ore bodies in asteroids is an open question. A lot of survey work needs to be done to answer this question.

Oh, and one more thing. When you blast rock on a largish planet like earth, the fragments fall back to the ground. This won’t happen on an itty bitty asteroid.

The talk about recovering water from asteroids to subsequently crack and make propellant is a large challenge all by itself.

I predict that civilization will slump back to a 19th century Dickensian-style world of robber barons and sharecroppers before any hardware gets to an asteroid.  Children will ask “Momma, what’s an iPad?” as they walk from their rundown subdivision to a quonset where they strip insulation from wire for copper to barter for food. It’s all so clear now …

Early Adventures with Nitrates and Tartaric Acid

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It is a misconception that renaissance alchemists were only concerned with the philosophers stone. Hermetic alchemy was an overlap of alchemical practice within a mystical or spiritual framework. This branch of alchemy and its practitioners are perhaps better known in the popular literature than the alchemists who might be regarded as more pragmatic experimentalists.

Many alchemists over history were very practical and quite occupied with their trade in medicaments, tinctures, distillates, and elixirs or with metallurgical and compounding endeavors.  Paracelsus is regarded as an early practitioner of iatrochemical work, but within a hermetical framework.  Agricola and Biringuccio were 16th century chroniclers of metallurgy that had a basis in earlier alchemical progress.

Consider an entry from a translation of The Laboratory, or School of Arts; in which are faithfully exhibited and fully explain’d, I. A variety of curious and valuable experiments in refining … VI. A dissertation on the nature and growth of saltpeter; … Translated from the German, by Godfrey Smith, published 1738.  In this volume, available from ECCO, Eighteenth Century Collections Online, contains a passage under the heading of “To prepare Aurum Fulmina__s” (two letters obscured). I have retained the archaic character “f” in place of “s” for the reader to enjoy.

To prepare Aurum Fulmina__s

Take Gold that is refin’d with Antimony, beat it to thin Plates, put it into a Phial or Matrafs, pour Aqua Regis upon it, then fet the Phial or Mastrafs upon warm sand, till the Aqua regis is diffolv’d as much of the gold as it is able to contain, which you will knw when you fee the Ebullitions ceafe, pour your Solution by Inclination into another Glafs, and if you fee there remains any Gold in the Matrafs, dissolve it as before with a little frefh Aqua regis, mix your Diffolution, and pour to it five times as much common Water, afterwards drop into this Mixture, by Degrees, the Volatile Spirit of Sal Ammoniac, or Oil of Tartar, and you will see the Gold precipitate to the Bottom of the Glafs, let it reft a good while for the Gold to settle, then pour off the Water by Inclination, wafh your powder with warm Water, till grows infipid, dry it to the Substance of a Pafte, then form it in little round Corns, the Bignefs of a Hempfeed, dry them by the Sun, if you put one of them into a Fire, it will fly and difperfe with a terrible Noife, and beat about with great Violence. [Emphasis mine]

It seems likely that the worker is trying to refine the gold by dissolution of the Sb/Au blend by complete dissolution in aqua regia, followed by what we would now regard as a reduction of the gold solution. Quenching the aqua regia would be expected to cause the gold to reduce and fall out as the native metal. But gold chemistry is not what is interesting in this account.

The Spirit of Sal Ammoniac, meaning either ammonia itself or ammonium chloride, would do as follows: the ammonium would ion pair with nitrate and, upon drying, leave a residue of ammonium nitrate, which is an explosive. Simple open burning of  small kernels material enriched in ammonium nitrate might be expected to deflagrate or pop, as indicated in the end of the description.

The Oil of Tartar, however, might have an altogether different fate when dissolved in aqua regia. Oil of Tartar is a concentrated aqueous solution of potassium (or Na) tartrate.  In solution with aqua regia, one would reasonably expect the two hydroxy groups of tartaric acid to form the dinitro ester if appropriate nitrating species are present. A nitrate ester group is a common explosophore and consists of O2N-O-C comprising an oxygen linkage between NO2 and carbon. This linkage is sensitive to low levels of stimulus, making compounds with such linkages susceptible to rapid or explosive decomposition. The nitrite ester is listed as an explosophore as well.

The nitration of tartaric acid is described in US patent 1,506,728. This patent teaches the use of the standard H2SO4 catalyzed HNO3 nitration of the tartaric acid diol functionality to form a dinitro ester via the standard nitronium ion formation. In the case of aqua regia, the presence of NO2(+) is questionable. Aqua regia is known to produce nitrosyl chloride, ClNO which dissociates to Cl2 and NO.  Literature on the nitration of alcohols to nitro esters in aqua regia is non-existant in Chemical Abstracts. There are a few citations describing aromatic nitration by aqua regia, but no clear description of nitro ester formation.  Indeed, there are many descriptions of direct extraction of gold from aqua regia using isoamyl alcohol with no warnings of explosive or nitro formation.

There are, however, reports of the use of ClNO to produce organonitrites when reacted with a monohydroxy alcohol (Journal of the American Pharmaceutical Association (1912-1977) (1932), 21, 125-8). It is possible that a tartaric nitrite was formed which may be energetic to some extent.

But perhaps the application of Occams Razor is needed. Potassium or sodium tartrate would be mildly basic and upon addition to a mineral acid solution, it would neutralize the acid in sufficient quantities, affording potassium or sodium nitrate (saltpeter). On evaporation of water, the saltpeter residues would be comingled with tartaric acid, comprising a fuel/oxidizer mixture.

Small quantities of crude nitrate esters, nitrite esters, or nitrate salts could have been present in the dried paste, giving the pyrotechnic effect described. The formation of energetic materials was not the primary purpose of the procedure, although the observed behavior of the residues was apparently compelling enough to document.

Spectrum, Spectra, Spectre

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I’m not feeling especially peevish just now, truly, but I will say that a linguistic habit I’m running into more frequently is beginning to rub me the wrong way. That habit is the misuse of the word “spectra”.

I hear many people using the word “spectra” as the singular form rather than the word “spectrum”.  Spectra is the plural form of the word spectrum.

The spectre of spectra as spectrum shines like a specular glare from a speculum mirror in the corner of my consciousness.

Thorium power. Will the US get on board?

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Everybody knows by now that China is flush with rare earth elements (REE’s), or at least to the uppermost extent that any country can be. And, everybody knows the market hijinks that China has planned with REE’s, namely, buy all the REE’s you want from them, as long it is in a value-added manufactured good.

What most folks are probably not aware of is that the ore bodies that carry the REE’s (Sc, Y, and the Lanthanides) are usually enriched in thorium and/or uranium.  So much so that no little amount of skill and equipment is needed to separate Th & U from the REE’s. The US and USSR developed much of this separations technology post WWII and for decades thereafter. Much of this art is in the US patent literature. The rest of it is buried in dusty, obscure volumes on library shelves.

The art of REE separation is arcane and somewhat isolated from the rest of inorganic chemistry owing to its specialized nature. Most of the separations art relies on leaching and elaborate solvent exchange schemes.  Ion exchange technology is also highly represented in this domain.  Few chemistry students are exposed to this science and most of the cold war era practitioners are retired, ailing, or deceased.

Chemistry students rarely see this art for another reason. It is generally practiced by engineers and metallurgists who seem to be in a perpetual phase separation from the standard chemistry curriculum. I would argue that this distinction is mainly cultural.

Back to the Chinese. While Americans have been busy yammering about drill-baby-drill, or following the escapades of reality show imbeciles or a thousand other idiotic distractions, we have failed to focus pressure on our government to consider technologies like thorium power or molten salt reactor technology.

While a gullible and frankly, cognitively impaired, vocal minority in the US accept that we have a right to $<3.00/gal gasoline, we are being distracted into the warm feather bed of self-congratulation and delusion about our supposed exceptionalism. I sense that our culture is beginning to show a type of exceptionalism that is not very admirable.

While American voters are being spun up into a frenzy again about commodity oil prices, China has been promulgating its national industrial policies. American industrial policy seems to be about lining the citizens up for accelerating consumption. China’s industrial policy emphasis seems to be about putting infrastructure and capacity in place for exports as well as anticipated internal consumption.

China has a substantial presence in mineral rich Africa. China imports copper ore from Peru and Chile. Not finished copper- but copper ore. China keeps the value added steps for its own coffers. Most distressingly, China is busily working on copper mining in Afganistan while our kids fight and die there in an intractable cultural shooting war. Did you get that?

China is mining in Afganistan and Americans are paying to die there.

While the US pays to make the world safe for commerce, China is spreading out over the world looking for scarce resources like copper under the umbrella of stability.  While China mines copper in Afganistan, the USA consumes copper in Afganistan in the form of brass bullet casings ejected over the landscape. Brass is an alloy of copper and zinc.

Is this a diatribe against all things Chinese? Absolutely not. If anything, China has skillfully mastered it’s range of control and made purposeful, long term plans to reach its goals. Like its plans for Thorium-based molten salt reactors. Thorium power is undergoing a bit more examination now, as described in this Forbes article.

Here is a point I’d like to get across. The present boom in REE exploration and mining is in a good place for thorium extraction. If thorium were to be part of the extracted value rather than a costly sidestream in need of segregation and remediation, then the subsequently improved economics of REE extraction and greater availability might translate to lower REE costs for users of rare earth metal technology.

There is a crucial synergy here that the US would do well to exploit. But it requires vision, long term planning, and regulatory flexibility in the handling, accumulation, and processing of thorium.  These attributes the US now lacks. The current lead pipe doctrines of American politics represents a critical systems failure of our culture. We cannot continue to regard middle-ground compromise as total forfeiture.

Chemistry Lab Accidents Reports from the Chemical Safety Board.

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Here is a link to a US Chemical Safety Board video summarizing several recent lab accidents.  If you have never visited or heard of the CSB, here is a link to their web site. Have a look around.

This link is to the case CSB case Study of the Texas Tech explosion with nickel hydrazine perchlorate. It has a nice illustration of the Swiss Cheese Model of safety. This model was devised by British Psychologist James T. Reason at the University of Manchester in 1990.

The degree symbol- Do we really need to keep using it?

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I had an evil thought just now as I attempt to write 2 reports simultaneously. Why do we keep using that superscripted circle in front of C (i.e., ºC) that designates “degree”?

What the hell? We don’t use it for the Kelvin temperature scale. And, who knows if the engineers use it for Rankine? The thing is useless like an appendix or a titular chairman. Get rid of it!

What do you think?