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Stewart Robert Hinsley wrote:
> I
>
>>
>
> This sort of thing has been investigated. Look for, for example,
> articles on double chlorides and solid solutions. In the particular
> cases of LiCl/NaCL and NaCl/KCl is appears that you don't get a
> crystal with more than trace quantities of a second alkali metal.
> Instead you would get separate crystals of the two chlorides. Or at
> least that's what the abstract at
>
> http://cat.inist.fr/?aModele=afficheN&cpsidt=16102068
>
> seems to imply.
>
> There are cases where two ions can be freely substituted in a crystal.
> An example that comes to mind is olivine, which is a solid solution of
> Mg2SiO4 and Fe2Si04. Although I seem to recall mention of ordered
> phases in solid solutions I expect that here the Magnesium and Iron
> ions are disordered. However olivine is orthorhombic, not cubic.
>
> A solid solution is favoured if the substituting ions are of similar
> charge and size. Li+, Na+ and K+ differ significantly in size.
>
> A classic cases of double salts are the alums, which are double
> sulphates of a singly charged ion (Na+, K+, Cs+, Rb+, NH4+) and a
> triply charged ion (Al+++, Cr+++).
I was looking for a system in a cubic or tetrahedral group (preferably
cubic as
it would be able simulate it with software fairly easy).
Maybe HCl ( not strictly ionic!) and LiCl would over come the
size difference problem. HCl abducts are well known in salt crystals.
As I remember Alums are pretty crystals and fairly common.
http://chemistry.about.com/cs/howtos/ht/alumcrystal.htm
http://chemistry.about.com/od/growingcrystals/ht/purplecystal.htm
http://scripts.iucr.org/cgi-bin/paper?S0021889875010588
"Sodium-chromium `anhydrous alum', NaCr(SO_4 )_2 is monoclinic, space
group /C/2//m/."
Monoclinc ( C2h is probably the point group of the unit cell?)
Low symmetry like this even in crystals is not a very promising
structure for fractal dimension experiments.
It looks like maybe a thought experiment and simulation would be ahead
of physical analogs.
At least until further research on models. Tetragonal systems with a
C4 axis and some other system
might work better ( works better with cubes!).
Trigonal crystal systems that are C3v might also be
worth while.
Transition metal substitutions like Cr, Mg and Fe do over come the size
problem, but also
are very close in attraction potential as well.
What is needed is a higher symmetry crystal with relative interchange of
ions.
One that can be adapted to some sort of Menger sponge simulation in a
random
A system like LiBr and KCl has four variables instead of just two but
might work better
for sizes.
Another thing is "cheapness" of the materials, so it can be duplicated
by many people ( like the bath tub and cleanser experiment for
sedimentation).
Full a tub with medium hot water , take a bath.
Before you pull the plug, take a lot of cleanser and salt it in the water.
Let it drain relatively slowly. ( probaly im****tant: as a rapid draining
doesn't allow the cleanser to
fall out as the water drains.)
Observe the patterns in the cleanser that sediments out.
This is essentually like sand in rivers and lakes.
Roger Bagula
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Stewart Robert Hinsley wrote:
<blockquote cite="midJIEl6cI1gb0GFwzF@[EMAIL PROTECTED]
" type="cite">I
<blockquote type="cite"><br>
</blockquote>
<br>
This sort of thing has been investigated. Look for, for example,
articles on double chlorides and solid solutions. In the particular
cases of LiCl/NaCL and NaCl/KCl is appears that you don't get a crystal
with more than trace quantities of a second alkali metal. Instead you
would get separate crystals of the two chlorides. Or at least that's
what the abstract at
<br>
<br>
<a class="moz-txt-link-freetext"
href="http://cat.inist.fr/?aModele=afficheN&cpsidt=16102068">http://cat.inist.fr/?aModele=afficheN&cpsidt=16102068</a>
<br>
<br>
seems to imply.
<br>
<br>
There are cases where two ions can be freely substituted in a crystal.
An example that comes to mind is olivine, which is a solid solution of
Mg2SiO4 and Fe2Si04. Although I seem to recall mention of ordered
phases in solid solutions I expect that here the Magnesium and Iron
ions are disordered. However olivine is orthorhombic, not cubic.
<br>
<br>
A solid solution is favoured if the substituting ions are of similar
charge and size. Li+, Na+ and K+ differ significantly in size.
<br>
<br>
A classic cases of double salts are the alums, which are double
sulphates of a singly charged ion (Na+, K+, Cs+, Rb+, NH4+) and a
triply charged ion (Al+++, Cr+++).
<br>
</blockquote>
I was looking for a system in a cubic or tetrahedral group (preferably
cubic as <br>
it would be able simulate it with software fairly easy).<br>
Maybe HCl ( not strictly ionic!) and LiCl would over come the
<br>
size difference problem. HCl abducts are well known in salt crystals.<br>
<br>
As I remember Alums are pretty crystals and fairly common.<br>
<a class="moz-txt-link-freetext"
href="http://chemistry.about.com/cs/howtos/ht/alumcrystal.htm">http://chemistry.about.com/cs/howtos/ht/alumcrystal.htm</a><br>
<a class="moz-txt-link-freetext"
href="http://chemistry.about.com/od/growingcrystals/ht/purplecystal.htm">http://chemistry.about.com/od/growingcrystals/ht/purplecystal.htm</a><br>
<a class="moz-txt-link-freetext"
href="http://scripts.iucr.org/cgi-bin/paper?S0021889875010588">http://scripts.iucr.org/cgi-bin/paper?S0021889875010588</a><br>
"Sodium-chromium `anhydrous alum', NaCr(SO<span
class="inf"><sub>4</sub></span>)<span
class="inf"><sub>2</sub></span> is monoclinic, space group <span
class="it"><i>C</i></span>2/<span class="it"><i>m</i></span>."<br>
Monoclinc ( C2h is probably the point group of the unit cell?)<br>
Low symmetry like this even in crystals is not a very promising
structure for fractal dimension experiments.<br>
<br>
It looks like maybe a thought experiment and simulation would be ahead
of physical analogs.<br>
At least until further research on models. Tetragonal systems
with a
C4 axis and some other system <br>
might work better ( works better with cubes!).<br>
Trigonal crystal systems that are C3v might also be <br>
worth while.<br>
Transition metal substitutions like Cr, Mg and Fe do over come the size
problem, but also <br>
are very close in attraction potential as well.<br>
<br>
What is needed is a higher symmetry crystal with relative interchange
of ions.<br>
One that can be adapted to some sort of Menger sponge simulation in a
random<br>
A system like LiBr and KCl has four variables instead of just two but
might work better<br>
for sizes.<br>
<br>
Another thing is "cheapness" of the materials, so it can be duplicated<br>
by many people ( like the bath tub and cleanser experiment for
sedimentation).<br>
Full a tub with medium hot water , take a bath.<br>
Before you pull the plug, take a lot of cleanser and salt it in the
water.<br>
Let it drain relatively slowly. ( probaly im****tant: as a rapid
draining doesn't allow the cleanser to <br>
fall out as the water drains.)<br>
Observe the patterns in the cleanser that sediments out.<br>
This is essentually like sand in rivers and lakes.<br>
Roger Bagula<br>
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