"Søren Astrup" skriver:
> Hvordan ophoper tungmetaller sig i deporte i naturen??? Hvordan kan man
> grave i jorden og finde en masse bly?? Og hvordan er jernen kommet i
> jernmalm??? Når der på et tidspunkt er så mange tungmetaller og andet skidt
> i naturen hvordan får vi det så samlet igen???
>
> Håber der er nogle der gider at svare! :)
>
> Med venlig hilsen Aske Astrup
Giver spørgsmålet mening? (Samlet af Bruce Hamilton):
1. Hawley's Condensed Chemical Dictionary - 10th Ed (1981)
Heavy Metal - A metal of atomic weight greater than sodium (22.9)
that forms soaps on reaction with fatty acids. e.g., aluminum,
lead cobalt.
Light Metal - in engineering terminology, a metal of specific
gravity less than three that is strong enough for construction
use ( aluminium, magnesium, beryllium ).
- Wow!, Aluminium is both light and heavy. maybe a later edition
corrects that?.
2. Concise Encyclopedia of Biochemistry - 2nd Ed (1988)
Heavy metal - All metals with a density greater than 5.
- Does not define " light metal, and tabulates heavy metal
biomolecules of Fe, Co, Cu, Mn, Mo, V and Zn. It notes
that Vanadium is essential for some life forms. That would
suggest that definitions involving biological toxicity could
be rather messy....
3. International Encyclopedia of Chemical Science (1964)
Heavy Metal - A metal having a specific gravity greater than 4.
Light Metal - A metallic element of small density, commonly one
with a density below 4.
4. Technology of Light Metals (1949)
" As the term "light metals" connotes, their outstanding
characteristic is their light weight or low specific gravity.
There is at the present time, no standard value of this property
recognised as a qualification for the title "light metal".
The upper limit to qualify for inclusion in the light class
lies in the range of specific gravity 3 to 5. Regelsberger's
figure of 3.8, or say 4, can be taken as a reasonable upper
limit of specific gravity for the light class, since there is
no commercially important aluminium- or magnesium-base alloy
with a higher specific gravity than 4..."
5. Webster's Third New International Dictionary (1971)
Heavy Metal - Metal with a specific gravity of 5 or over.
Light Metal - Metal with low density. e.g., Al, Mg, Ti, Be.
Ligesom der er forskellige nyere overvejelser.
http://www.osha.gov/SLTC/metalsheavy/
http://www.iupac.org/publications/ci/2001/november/heavymetals.html
Jeppe