From: David Lauter (djlauter@hotmail.com)
Date: Sat May 31 2003 - 12:17:39 PDT
From: "David Lauter" <djlauter@hotmail.com> Subject: Re: urea and the N cycle Date: Sat, 31 May 2003 12:17:39 -0700 Message-ID: <Law15-F27hiNaJrHREK0001243e@hotmail.com>
Urea is commercially important as a fertilizer because of its high
percentage of nitrogen, higher than ammonium nitrate and ammonium sulfate.
Like in our liver, urea is commercially produced from ammonia and carbon
dioxide. Our students should know about how we get the ammonia, the Haber
Process, which is the production of ammonia from N2 and hydrogen. Developed
by Fritz Haber at the beginning of the last century, it saved our planet
from a dependence on nitrogen minerals. Up until then, the supply of
N-fertilizer was a huge limitation on food production. Basically we were
all fertilizing plants with other plants (organic farming) and minerals from
Chile. This practice was anything but sustainable.
The importance of the Haber process can't be underestimated. Prior to
Haber, the lack of food was well described in the writings of the great
european novelists. Our U.S. history was not immune from the lack of a
cheap N source. The expansion of the South and the settling of the West
were in large part a search for fertile ground. Today the Haber Process is
even indirectly responsible for the surplus in "organic" fertilizers, which
in turn allows the consumers of organic food to have the delusion that they
are promoting sustainable agriculture. Teach the N-cycle. You can't get
something from nothing (2nd law, but with N instead of energy).
David Lauter, with apologies for getting on my soap box
George Washington High
SF, CA
search>From: "Pinhole Listserv" <pinhole@exploratorium.edu>
>To: "Pinhole Listserv" <pinhole@exploratorium.edu>
>Subject: Pinhole Digest #1229 - 05/30/03
>Date: Fri, 30 May 2003 00:20:01 -0700
>
>Pinhole Digest #1229 - Friday, May 30, 2003
>
> Urea
> by <SFPhysics@aol.com>
> aurora alert
> by "Paul Doherty" <pauld@exploratorium.edu>
> Chemistry Job Opening
> by "Art Fortgang" <afortga@yahoo.com>
>
>
>----------------------------------------------------------------------
>
>Subject: Urea
>From: <SFPhysics@aol.com>
>Date: Thu, 29 May 2003 04:46:26 EDT
>
> >Subject: Urea
> >From: "Adam Singer" <adamsinger@earthlink.net>
> >Date: Tue, 27 May 2003 09:57:59 -0700 (PDT)
> >So my mother was going through my late father's belongings (he was a
>molecular biologist and an avid gardener) and she came across a supply of
>crystalized
>urea. Does anyone have any idea what this may have been used for or is
>there
>any possible classroom use for this?
> >Thanks!
> >-- Adam Singer
>
>Hi Adam:
>
>I see no one wanted to tackle urea. Urea (CO(NH2)2) is excreted in the
>urine
>of animals as a byproduct of metabolizing plant protein. It can be added
>to
>soil where it reacts with water to give CO2 and ammonia. The ammonia is
>usually formed into an ammonia salt which is either taken by some plants
>directly
>through their roots to become plant protein again or by bacteria which work
>on
>the ammonia to release the nitrogen and its compounds into the soil and
>air.
>It is a part of the Nitrogen Cycle. Clay soils that are highly acidic
>sometimes have urea powder added to balance them and provide nitrogen if
>memory
>serves me.
>
>As for what you might do with pure crystalline powdered urea in the
>classroom, I must admit ignorance and leave this to the chemistry and
>biology people.
>University types might do Hartree-Fock molecular crystal interaction
>studies
>but that likely doesn't translate well down into the grammar school
>curriculum.
> ;-)
>
>Hope that helps,
>
>Al Sefl
>Full of the usual hot air, of which 78% is Nitrogen...
>
>----------------------------------------------------------------------
>
>
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