Pique the Geek 20120624: Lithium, Primal and Essential

Lithium, the element with the atomic number (Z) of three, is as old as the universe.  It, along with hydrogen and helium, were formed at the time of the Big Bang, making it primal indeed, although much of the lithium that we encounter was synthesized in stars.

Lithium is much less common in the cosmos than it should be, and that is in part due to the fact that the two stable isotopes, ⁶Li and ⁷Li, are much less stable than many other light nuclei.  This might sound contradictory, but there is a property of atomic nuclei called binding energy per nucleon that measures the stability of nuclei.  Both stable isotopes of lithium have binding energies per nucleon lower than any other nuclei except for deuterium, tritium (which is radioactive), ³He, and of course hydrogen which has a zero binding energy because there are no neutrons to require binding.

This makes both stable isotopes of lithium easy to convert to other elements, notably the reaction betwixt a proton and a ⁷Li nucleus which transforms them to two helium nuclei at relatively low temperature.  There was not very much ⁶Li formed in the first place, because it is an odd/odd nucleus and those are particularly unstable for the most part.  Elements with an odd Z tend to be less stable than ones with an even Z, and elements with both an odd Z and an odd number of neutrons are particularly unstable.

In addition, there are not many common processes that form lithium, the most common one being the comparatively rare interaction betwixt a ³H and ⁴He that forms ⁷Li.  The point is that lithium should be much more common than it is.  That is not good for us.

Lithium is the second metal in the periodic table, hydrogen being the first.  Well, hydrogen is thought to exist in the metallic form in the gas giant planets, like Jupiter, because of the enormous pressures required to force its atoms close enough together for the metallic state to form.  Lithium is the least dense terrestrial metal, and is the first member of the alkali metals.  Its density is just a little over half that of water, and it reacts vigorously with water to form lithium hydroxide and hydrogen gas.

I have a personal affinity for lithium.  It was first discovered by Johan August Arfwedson, who at the time was what we would now call a graduate student or a postdoctoral fellow working for the great Swedish chemist Jöns Jakob Berzelius.  My own Ph.D. genealogy can be traced back to Berzelius.  I need to get with my major professor and see if I can get the entire thing.  If I do, I shall post it.  It was Berzelius that first used the name “lithium” for this element, in 1817.

However, the free metal was not isolated until William Thomas Brande used electrolysis to win the free metal in 1821, a technique pioneered by the brilliant British chemist Sir Humphrey Davy.  Once it was isolated, it was found to be chemically similar to the other alkali metals like sodium and potassium, but less reactive in most cases.

So, why do we use lithium?  There are scores of uses for it, in many diverse areas from nuclear technology to lubrication to medical ones.  Perhaps the first major use of lithium was for lubricating greases that could withstand high temperatures and pressures for aircraft lubrication during World War II.  Those are actually soaps made with lithium instead of sodium, with oily additives to increase lubricity.  Because lithium is a very small, hard ion (the positive one charge is distributed in a very small volume), lithium soaps melt at higher temperatures than sodium ones (most bath soap is a sodium salt of animal or vegetable fat).  Potassium soaps are often liquid at room temperature.  The high melting points of lithium soaps are important to keep the greases solid enough not to be thrown off of fast moving parts at high temperatures.  For those of you who pack your own wheel bearings on your automobiles, you will note that for axles with disc brakes lithium grease is recommended.  Disc brakes generate more heat, everything else equal, than drum brakes, so the wheel bearings need a higher temperature grease.

Once by far the major use for lithium, greases still consume around 12% of the lithium supply.  Unfortunately, lithium uses in lubricants is consumes it and almost none can be recovered and recycled.  The importance of this will become apparent later.

Lithium is also used to make glass.  It has several properties that improve glass, including making it have a lower melting range.  This is important from an energy conservation standpoint.  It also helps to reduce breakage due to thermal expansion effects.  Interestingly, another element, boron (Z = 4) also reduces thermal expansion effects and is a key ingredient of real Pyrex glass.  (New US glass bakeware is NOT borosilicate glass, but 30 years ago it was.  Corning licensed the term Pyrex to other companies for bakeware that does not contain boron).  Interestingly, boron is another element that is less common than it should be.  Over a quarter of the lithium produced goes into glass, and most of it is not recoverable nor recyclable either.  Glass use accounts for about 29% of the lithium produced, so when combined with grease that means that we essentially throw away around 42% of the lithium produced.

The second largest use of lithium is for rechargeable and nonrechargeable batteries.  Lithium is uniquely suited for batteries because of its low mass and very high electrochemical potential.  A lithium battery can produce lots more power than conventional batteries, and many of them have long lives and can be recharged quickly.  This application consumes around 27% of the lithium produced, and the lithium is fairly easily recovered and recycled.  I expect that that fraction will increase rapidly in future, and that is a good thing since most all of the lithium can be recovered.

That is IF people would take their spent batteries to a recycling center.  I think that a costly deposit should be imposed on lithium batteries, both single use and rechargeable, as a function of the mass of the lithium in them.  It makes no sense at all just to throw them out with the baby diapers.  By the way, when we were raising infants, the former Mrs. Translator and I used cotton diapers except when traveling.

If you are using a laptop to read this piece, the chances are almost 100% that the battery in it is a lithium ion battery.  In these batteries, the carriers of the positively charged current inside the battery are lithium ions, where in most all (there are some exceptions) other batteries the positive currents carriers are protons, aka hydrogen ions.  Most people think that in a lithium ion battery metallic lithium is ionized during discharge and redeposited during recharge, but that is not the case.  The lithium really does not enter into the electrochemical reactions per se, but rather just carries the current produced by some transition metal, such as cobalt.  During charging, Co³⁺ is oxidized to Co⁴⁺, and that requires electrons (thus the charger).  The lithium ions are transported from the cathode (positive electrode) to balance the extra negative charge on the Co⁴⁺.  During discharge, the reverse happens and the lithium ions are transported to the anode (negative electrode) to maintain charge balance.

Interestingly, a new design of battery is being developed that uses potassium ions instead of lithium ions.  It may well be that in 20 years (or even less time) that lithium ion batteries are as obsolete as nickel cadmium batteries are now.  Note that lithium ion batteries have only been on the market since 1991.  Battery technology is rapidly advancing.

There is another family of lithium batteries, but they are not rechargeable.  The most common type uses metallic lithium as the anode and manganese dioxide as the cathode.  In these batteries, the metallic lithium reacts by giving up an electron, just like in the carbon/zinc battery the zinc releases electrons.  These batteries are sort of dangerous, and they will react violently with water if opened.

This brings me to a completely different use of lithium, and that is in organic chemistry as a reducing agent.  Lithium “likes” to donate electrons, and many extremely useful reagents can be made by reacting metallic lithium with alkyl halides to form organolithium reagents.  These compounds are used as extremely strong organic bases or to couple with other organic molecules to make bigger molecules.  Because lithium is a powerful reducing agent, it is also used in a couple of illicit synthetic schemes to make methamphetamine from ephedrine or pseudoephedrine.

This presents a problem for the legal purchase of lithium batteries.  Some states have limited the number of lithium batteries that a person can purchase at a time, just like almost all states have limited the amount of pseudoephedrine that can be purchased at a time.  The old joke about being able to get everything that you need to make methamphetamine at Wal-Mart is literally true.  I am not giving away any restricted information because the meth cooks already know what I just said and much, more that I have chosen not to repeat.

A former very large use for lithium was in nuclear weapons technology.  It turns out that both stable isotopes form tritium when bombarded by neutrons, and the heavier isotope actually returns the neutron!  The lighter isotope is more important for thermonuclear reactions, and the fuel for fusion is the binary compound ⁶Li deuteride, or LiD.  When compressed and irradiated with neutrons from a fission reaction, the lithium is transmuted into tritium and the extreme temperatures and pressures cause the tritium to fuse with the deuterium, creating ⁴He, a neutron, and an enormous amount of energy.  This is a very clever was to produce tritium, because tritium itself is radioactive with a half life of only 12.32 years and would have to be replaced constantly.  By forming it from a stable isotope of lithium, it is made only when needed, giving such an arrangement an essentially infinite life.

It turns out that the big stockpile of ⁷Li that the government had was a  product of the nuclear weapons race during the Cold War.  The heavier isotope was removed, leaving the lighter one for nuclear devices.  This was stockpiled and after the arms race the government began selling it off, depressing prices just like happened for helium as explained last week.  Now that the stockpile is essentially depleted, new lithium has to be found.  The US was once the largest producer (for the arms race), but has comparatively little.  Fortunately, most of the largest producers are friendly with the US.

There are many other uses for lithium, but I shall close with the medical ones.  It is primarily used to treat bipolar disorder and also some other psychiatric conditions.  The mechanism of action for lithium in these disorders is still speculative, but from many years of clinical use it is known to be effective in many people, in particular for controlling the manic phase of bipolar disorder.  People taking lithium need to have serum lithium levels checked frequently, because the toxic dose is uncomfortably close the the therapeutic dose.  Lithium can cause dehydration, and that starts a dangerous feedback loop because dehydration further concentrates lithium levels.

Until 1950 the soft drink 7 Up had lithium citrate in it.  That was removed when concerns about high lithium intake were realized.  The original name for it was Bib-Label Lithiated Lemon-Lime Soda when it was introduced in 1929.  The origin for the name 7 Up is unclear.  Some say it is because of the seven main flavor ingredients, but I shall proffer my hypothesis that it is from ⁷Li, the more common isotope.

Unlike helium, lithium is quite recyclable in many cases, in particular batteries.  Since this promises to be the largest use for lithium for the foreseeable future, prospects for stretching the lithium supply are better than for helium.  However, it is a finite resource and should not be wasted.

Well, you have done it again!  You have wasted many more einsteins of perfectly good photons reading this light piece.  And even though Issa realizes that he is just plain wrong on his witchhunt when he reads me say it, I always learn much more than I could possibly hope to teach in writing this series, so please keep those questions, comments, corrections, and other feedback coming.  Tips and recs are also appreciated.

I shall stick around for comments as long as the volume warrants tonight, but with this caveat.  There is a very good chance that I may visit someone this evening, and if that be the case it might be late before I can answer.  In any event, I shall return tomorrow evening for Review Time.  Wish me luck in not being around to comment until late, please!

Warmest regards,

Doc, aka Dr. David W. Smith

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