I have thought long and hard about this and honestly I'm more then a little nervous about this decision, but I think it is the right one and one I hope that the community will support. For those that do not know a long long time member of the daily kos community by the name of Translator had a series called 'Pique the Geek'. I've not had the opportunity to read every one of them but it seems like he wrote about everything and any thing in science. What I would consider his most ambitious project was to write about every element in the Periodic; sadly Translator is no longer with us.
That brings us to me, back in September I wrote what was intended to be a set of 3 diaries on Stoichiometry. I never finished it and that mostly had to do with the depth of the material and my time constraints at the time. I had already intended to go back to writing about chemistry when I found out about Translator.
I have decided, in tribute to both Translator and what seems to me was his mission to share knowledge with the community to finish his work. As such I will continue where he stopped with Aluminium today. For now I intend to do one element every Sunday and one every Monday night at the very least with the possibility of another element during the week. Though that will depend on time constraints.
So please join me below as we look at Aluminium one of the few elements I know of with 2 distinct pronunciations and one of the more interesting metals.
Aluminium has only 1 stable isotope, Aluminium-27 and though Aluminium-26 has a large enough half life (7.166*10^5 years) that it could conceivably be found in nature it is not found in any abundance . Thus Aluminium-27 has an abundance of 99.99+% with Aluminium-26 making up the remaining percentage. Interestingly all other isotopes of aluminium are quick decaying isotopes with half lives ranging from a few minutes to nanoseconds. In terms of overall abundance aluminium is the third most abundant element found on the earth
Aluminium-26 is formed in the upper atmosphere by the collusion of cosmic rays with argon under a process called spallation. Spallation is just the process of forming elements using the energy of cosmic rays. The rays are energetic enough that they can stripe off electrons, neutrons, protons even whole parts of the atom (by alpha radiation). The resulting radiation is highly energetic and in turn collides with other atoms. Frankly the process is detailed enough to warrant it's own diary or more but the short of it is that these collisions allow for elements to become other elements. This actually is why ozone is so critical but more on that later.
The uniqueness of Aluminium-26's synthesis combined with it's lengthy half life actually makes it very useful as a method of historical dating. For example the ratio of Aluminium-26 to Beryllium-10 has been used to study soil transportation and erosion as well as burial and storage. Further because the synthesis can not take place naturally on earth it has also been to date when meteorites and other cosmic objects fell to earth. This in turn has lead to a number of discoveries about cosmic objects and the formation of our planet. It has also been used in number of other dating methods ranging from manganese nodules and glacial ice.
Aluminium-27 (which for convenience I will hence forth refer to as Al) is just as interesting. Despite it's overall abundance AL is so chemically reactive that it does not generally occur on its own. Instead AL is found combined with numerous other metals with the chief ore being Bauxite and in fact this is generally how Al is processed into a usable form using what is known as the Bayer Process. The process named after the man that invented it transformed the AL industry. Before the process Al was rare and expensive, in fact a bar of pure AL was more expensive then a bar of gold and in fact the Washington Monument was constructed at a time when 30 grams of Al would be equal to the average wages of a worker on the project. It has also been reported that monarchs of the day would in fact give their most distinguished guests utensils of pure Al while less distinguished guests would have 'to make do' with gold utensils.
Why exactly was Al so valuable? As is often the case it was a combination of difficulty of extracting it combined with high demand. Al salts had been used since Roman times as dyes and for the longest time any dye was extremely important(for those curious examine the history of royal purple). In point of fact Al is still used in paints today because of it's reflectivity. Further when Al was first isolated as a metal in the mid 19th century it was found to have many qualities that make it extremely important in building which only added to its value. For example Al can experience over a 20 fold increase in its yield strength (which as you may imagine is the point at which the material begins to deform) if not more depending on the alloy. This combined with the relative lightness of the metal, it's resistance to corrosion and its high malleability all make it very attractive as a building material. Now I know what you're thinking, how can a metal that is so reactive that it will react with just about anything be resistant to corrosion? Well in this case it is precisely that high level of reactivity that provides the resistance. Al, even 'pure' Al that you see today in aircraft or building use actually has a thin layer of Al oxide on the surface. How thin are we talking? Molecular thin and it is the strength of the bond between Al and oxygen in this layer that is what gives Al it's resistance.
All these factors (combined with the fact that as with any metal it's both thermally and electrically highly conductive) have lead Al to being one of the most widely used metals in our modern world. Thus it is fortunate that even with the high rate of use the known stocks of Al in the world are sufficient for centuries at current use and that Al is a 100% recyclable material (meaning that you can recycle it without any loss in it's native properties).
Oddly aluminium compounds seem to have no major role in biochemical systems despite it's abundance. At the same time though the data to date indicates that the toxicity of Al is extremely low though as with really any element there is eventually a point where the body is impacted. As to organometallic compounds there is really little known about them with the first organoaluminium compounds first being discover in the 1850s but it would be about 100 years later before anyone would discover a direct synthesis (organometallics is the study of carbon-metal complexes and is an area of intense research in general).
However one of the most important Al compounds is an inorganic compound commonly called LAH which stands for lithium aluminium hydride. LAH is a powerful reducing agent and in fact hydride indicates that the hydrogen is in it's anionic form which is not how hydrogen wants to be. LAH in its pure form will react violently with water even if it is just the water present in the atmosphere. The importance of LAH just can not be understated, there are numerous reactions that will either not occur quickly enough or at all without the presence of LAH.
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So I think in the interests of not going overboard that is more then sufficient introduction to Al. Unfortunately I work nights and as such this will post while I am sleeping but please leave feedback both on the overall series and this entry. I will respond to everyone as soon as I am up. I want to provide enough information to be interesting but I don't want to bore everyone.