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qdung92ct
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[*] posted on 16-3-2012 at 22:39
Crystallization


Hi

I'm going to do a gift for my friend and I got an idea
I wanna make something that is formed from the recrystallization of solutions (may be Copper II Sulfate or the Zinc ionic)

So can I control the recrystallization with form that I want ?

For example, the crystal flower

Thanks
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Hexavalent
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[*] posted on 17-3-2012 at 01:04


Possibly; look into using different containers and cooling patterns.

Cooling a hot solution quickly produces very small crystals, yet cooling very slowly, maybe even by putting the beaker in a thermos, will produce larger ones.

The best crystals, of course, will come from allowing a RT solution to crystallize very slowly on its own.

Read up a bit on it, there are plenty of YouTube videos and instructions explaining questions just like this.




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blogfast25
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[*] posted on 17-3-2012 at 06:29


Growing crystals that are worthy of a gift is a business of patience. In essence the slower you grow them, the more 'perfect' they tend to be. Also: purer materials tend to give more perfect crystals, so a quick recrystallisation of your starting material can pay off handsomely later on.

Popular crystal growing materials, often found in commercial crystal growing kits, are alum (potassium aluminium sulphate dodecahydrate) and ammonium dihydrogenphosphate, both of which are fairly OTC. There are clear (white) but can be coloured with food dyes for special effects: green alum looks a bit like emeralds, for instance.

As Hexavalent said: search the web and Utoob for manuals.


[Edited on 17-3-2012 by blogfast25]




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dann2
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[*] posted on 17-3-2012 at 07:26


Not exactly crystal growing but..........
A great way to create impressive looking art pieces is to 'grow' metal 'trees' from solutions of the metal salts using electricity.
I did this years ago using Copper Sulphate and some Copper wire as the Anode and the Cathode (+ & -).
You can get exquisit looking Copper trees growing from the wires if you use some diodes and resistors as per the diagram (as far as I can remember). The trees care extreamly dendritic and complex and will look very pretty if left in the original growing solution.
Dann2



[Edited on 17-3-2012 by dann2]

Cu_dendrites.bmp - 34kB
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Bot0nist
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[*] posted on 17-3-2012 at 10:45


Not a DC current source dann2?



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MrTechGuy1995
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[*] posted on 17-3-2012 at 12:08


Quote: Originally posted by Bot0nist  
Not a DC current source dann2?


It converts to DC through AC.
One line is Live, and the other is "Ground".
The symbol that looks like a "Play next to a box" Is a diode. Put 2 of them together and you get a Bridge Rectifier.
Basically a Single Direction Current that has a wave of:



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[*] posted on 17-3-2012 at 12:24


Thank you Mrtechguy! Electricity is definitely not my strong suit. It time I started to read up

[Edited on 17-3-2012 by Bot0nist]




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Arthur Dent
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[*] posted on 17-3-2012 at 14:42


Please note that many "large" crystals may look beautiful but they often have a fatal flaw...
they are brittle as hell and break apart quite easily.

I tried with Manganese Chloride and Copper Sulfate and even after a good drying, they tend to fracture very easily so don't think you'll make something as hard as a Topaz or Quartz crystal cluster unfortunately.

Maybe there are other chemicals that produce more sturdy crystals... plain old NaCl might be the trick.

Robert




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[*] posted on 17-3-2012 at 15:15


Quote: Originally posted by dann2  
...
You can get exquisit looking Copper trees growing from the wires if you use some diodes and resistors as per the diagram (as far as I can remember).[Edited on 17-3-2012 by dann2]


Your circuit will produce an AC current, though with diode-drop votage offsets near zero crossing. Full-wave rectification with two diodes is accomplished with a centre-tapped transformer; lacking that you need four diodes connected in a bridge configuration.

To get the pulsed-DC waveform you show, simply remove one of the diodes.

-Boby
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[*] posted on 17-3-2012 at 16:33


The silver tree is a classic demonstration of metal growing:

http://www.unitednuclear.com/silvertree.htm

Maybe if drained and washed with alcohol it could be backfilled with acrylic and preserved.

Another interesting metal 'tree' that I grew involved tin rods. I had large bars of tin used for solder and I tried to dissolve a whole bar in hydrochloric acid. Over the days it dissolved and then strangely started to plate back out on the bar in the form of needles, less at the top, more at the bottom until it did start to resemble a tree. It was very pretty, turns out the tin had 2% silver in it to help it flow. I am assuming this was again silver crystals.

As Hexavalent stated above, allowing a solution to grow crystals slowly is a must for nice well formed crystals. It took the better part of 8 months for a large (2L) solution of copper sulfate to evaporate entirely at room temp but I ended up with some crystals that would look nice in jewelery and could be cut and polished if desired.




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[*] posted on 17-3-2012 at 17:54



The circuit I give above was from a dry-cell-battery-rejuvenator circuit.
I was messing around with it years ago and (cannot remember quite why) then started to mess around with solutions of Copper Sulphate and Copper electrodes.
The circuit gives a small amount of current reversal (depending on size of resistors) during each cycle (visualize small humps under the line in MyTechGuy1995 diagram). This seemed (I thought) to give more dendritic 'trees' than a straight DC. Perhaps DC is just as good at giving lots of dendrites/branches. Using one diode in my circuit will give you DC, or use a bridge retifier or just a plain old purchased DC power supply.

Crystals and Copper trees or Silver trees always seem to look better when in solution. When you take them out they often loose some of their beauty. DANN2
D
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[*] posted on 18-3-2012 at 17:33


BromicAcid: I saw a journal article the other day mentioning the recrystallization of tin from hydrochloric acid solutions but I cannot for the life of me re-find the said article. It mentioned that alloyed tin worked better, and that it was a result of some equilibrium between the tin metal and the tin (II) chloride produced upon the action of acid.
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[*] posted on 19-3-2012 at 06:19


Quote: Originally posted by BromicAcid  
The silver tree is a classic demonstration of metal growing:

http://www.unitednuclear.com/silvertree.htm

Maybe if drained and washed with alcohol it could be backfilled with acrylic and preserved.


I've done this demo a few times, and the tree is extremely fragile. The crystals are just so tiny and they don't adhere very well to the copper wire, so they tend to fall off at the slightest bump. I agree it would be very beautiful encased in acrylic, I just don't think the tree would survive the process.
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