As I've previously indicated on this blog, I am primarily an AQUEOUS inorganic chemist. As such, I've prepared a wide variety of aquated metal complexes over the years, but I've never paid much attention to solid hydrate chemistry. And that's a shame, since there is a lot of good chemistry in that area, some of which I'm dealing with right now.
A few months ago, we decorated our ceilings with crown molding. Unfortunately, the original builders of our house placed the water pipes too close to the ceiling, which meant that two months after the crown molding was added, the FOUR nails which had punctured the pipes rusted and caused the pipes to leak. The resulting repair left a hole in the ceiling which was my job to fix. The material of choice for this type of repair is drywall (sometimes called sheetrock). Drywall is prepared by mixing CaSO4 · 1/2H2O with water to form CaSO4 · 2H2O, a hydrate with enough strength to be used to construct walls. Considering the fact that the added water forms no bonds other than hydrogen bonds, it's a little surprising that the resulting hydrate is so stable.
Of course, the strength of CaSO4 · 2H2O is nothing compared to that of another well-known hydrate. Cement begins as a mixture of CaO and SiO2 in various proportions, which is then reacted with water to form a calcium silicate hydrate.
2 Ca3SiO5 + 7 H2O —> 3 CaO · 2 SiO2 · 4 H2O +3 Ca(OH)2
Actually there is an entire series of hydration reactions which occur during the hardening of cement, with reaction times ranging from hours to weeks. Again, the strength generated by the formation of a hydrate is simply amazing.
Another hydrate with interesting chemistry is methane hydrate. Containing 5-6 molecules of water for every molecule of methane, this material can be found in huge quantities along the ocean floor. Wiki link here. It has been described as both a huge, untapped energy reserve and a major source of greenhouse gas. The latter description has become more significant as the temperature of the oceans continues to rise, since methane hydrate is only stable at low temperatures. It's also been used to explain the disappearance of ships in the Bermuda Triangle. What more could you ask from a simple compound?
Anyway, the ceiling is fixed.
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4 comments:
Hydrates are definitely interesting and important, and of course cement/concrete is one of the most important substances in human civilization.
One small error fix, in your last paragraph you say "Containing 5-6 moles of water for every molecule of methane,"
*WOW* that's a lot of water!!!! :)
Anyway, it would be interesting to harvest these hydrates from undersea hydrate beds, somehow keep it solid in bringing it to the surface, and make syngas out of it in an IGCC power plant, or whatever else you want to do with methane or syngas. It's an untapped source of hydrocarbons.
There are several comments that I would like to add regarding these undersea clatherate beds ==
First is the source of Methane. Anything that has grown, from yard clippings to a decaying body, produces methane as it decomposes. Methane from permafrost is a decay product. Methane from the deep ocean (methane hydrate) is totally different. Methane from oil wells is yet a different composition. These must be recognized as such and understood as to their manner of existence, production, and/or release.
Deep sea Methane appears to be the waste product of a bacterial process, and therefore, is a renewable resource!!! It is a relative clean product of our environment. It has recently been produced in commercial quantities by Japanese scientists in Canada.
Oil well Methane is a very dirty gas -- it is methane with huge amounts of sulfur and other noxious gases mixed with it.
The Methane sometimes reported as "Bubbling up from Undersea Permafrost" is a decay product.
Our biggest concern is with CO2 in the atmosphere if you believe the current crop of media pundits. Actually however, it is the deep sea methane that bubbles up continually, and has for the past eons. It disassociates into CO2 shortly after reaching the surface.
What really concerns modern scientists and their political friends is the Drastic Global Climate Change that has taken place at least five different times during the last 400,000 years. Our present cycle is the only one during which man has been a factor!
The methane gas that bubbles up continuously from the deep ocean sources (which in turn disassociates into CO2) is the true source of the "Greenhouse Gas" that has operated in the previous five interglacial cycles -- all of which have been extinction cycles.
These are NOT man made effects, and it IS TOO LATE to change our present cycle, We can only learn to adapt!
JCSpilman, Huntsville, AL a.k.a.Shamus12017
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REFERENCES
There are several prime references associated with the material that I have covered, if ever so briefly.
(1) Earth’s Changing Climate. Lecture Series by Dr. Richard Wolfson, the Benjamin F. Wissler Professor of Physics at Middlebury College. This is a six hour lecture series (12 segments of 30 minutes each) on two DVDs produced by The Teaching Company of Chantilly VA 20151-1232.
www.TEACH12.com.
This series covers in-depth detail of the science and methodology of climate change. It is not an advocacy program. Interestingly, Dr. Wolfson does not even mention Methane-Clatherate in this lecture series -- knowledge on that subject is almost too new to have been included.
(2) Fire in the Ice. Quarterly Journal , U.S.Department of Energy, Office of Fossil Energy, National Energy Technology Laboratory. Also known as Methane Hydrate Newsletter. Recommended reading is all issues to current issue from about 2000 forward. This is the best of several technical journals devoted to the science of Methane Clatherates.
http://www.netl.doe.gov/about/index.html
(3) HIGH TIDE by Mark Lynas. Picador, 175 Fifth Avenue, New York, NY. 10010. ISBN 0-312-30365-3. This well written book clarifies the problems of Global Warming “… The American People have been subjected to one of the most pervasive misinformation campaigns ever undertaken …”
www.picadorusa.com
JCSpilman
Shamus, thanks for the references.
markmier, thanks for pointing out the typo.
I represent a large developer in Florida with some of the bad Chinese drywall. We need a chemist experienced with drywall to test it. Any suggestions?
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