Henry Vest wrote:
> Er der nogen der ved noget nærmere om dette og kan forklare lidt om det?
> Eller evt. give nogle relevante links.
Artiklen:
http://www.sciencemag.org/cgi/content/full/306/5704/2013
8 Splish, Splash. After a century of intense scientific study, water still
gives researchers much to scratch their heads about. This year, a flurry of
papers on the structure and chemical behavior of this familiar substance
revealed results that, if they hold up, could reshape fields from chemistry
to atmospheric sciences.
First and most controversial, a team of researchers from the United States,
Germany, Sweden, and the Netherlands reported that the 100-year-old picture
of the structure of liquid water might be wrong. Theorists thought slight
charge differences between oxygen and hydrogen atoms pulled liquid water
into an extended network, with each water molecule bound to four others in
a tetrahedral pattern. But the team's synchrotron x-ray results suggest
that many water molecules are, in fact, bound to only two neighbors. Don't
rewrite the chemistry textbooks just yet: More-recent x-ray data back up
the original structure, and debate will likely rage through 2005.
Another dispute centers on where ions in a large body of water hang out. Do
they reside at the surface or get sucked into the interior? Conventional
wisdom says electrostatic forces at the water's surface repel ions that are
abundant in seawater, forcing them to go deep. But researchers tracking sea
salt particles in the air over Los Angeles say the particles are so rich in
halides (chemical relatives of fluorine) that those ions must be present on
the water's surface. This year, computer simulations supported the idea. If
true, atmospheric scientists may have to ponder new types of chemical
reactions occurring on the surface of aerosol particles.
New experimental techniques are solving other mysteries. In April, a team in
California reported that firing femtosecond bursts of electrons at water on
a silicon surface had revealed crystallite-like ice structures that help
bind water to the surface. And other groups used improved methods for
making and tracking water clusters to determine how electrons and protons
dissolve in water, providing new insights into aqueous chemistry. At this
rate, water researchers won't be swimming in circles 100 years hence.
--
Mvh. Carsten Svaneborg
http://www.softwarepatenter.dk