Growing large silver crystals

[peter i]

Running .900 silver in your electrolytic refining cell will quickly contaminate your electrolyte as I understand the process.

Thats what I was afraid of. Well then I'll have to go the nitric acid route and use the electrochem to purify. further

Welcome to the forum.... but when you post something that is not related to a thread, please do it in a separate thread.

This one is about growing large silver crystals, NOT about basic electrolytic refining of 90% silver alloy.
:|
(Please do not add more "noise" with an apology. You are a new man, and I have forgiven you)


I'm about to terminate the present experiment. It involved using a 6cm exposed wire for crystallisation rather than the previous 5mm (all other parameters equal)
The result is nice but small crystals.... and it ended up growing an "arm" from the cluster to the dissolving lump.

Looks fun, I'll take a picture before harvesting it.

 

[shelly88813]

Wonderful post...

 

[HAuCl4]

Nice, beautiful crystals!.

Have you tried having just one crystal from the beginning and actively trimming all the rest?. It works for vines to make the plant stem stronger!. If there is only one, there is only one!.

I believe the key is slow growth and frequent mechanical pruning (more frequent pruning at the beginning). Try very low voltage 0.25-0.5 V, low concentration of nitrate in distilled water, and cut off mechanically any "branches" that grow from the center crystal as soon at they start.

You'll have to nurture that baby, especially at the beginning when it's weak and small!. :shock:

 

[peter i]

The problem is, that new crystals happily nucleate on the faces of the already formed crystals. Pruning could have some effect, but will not solve the basic question of which parameters will cause limited nucleation and thus growth of large crystals.

My latest experiment has been with 0.6V, saturated AgNO3, low temperature (5-10 °C) quite a bit of copper in the solution and a limited available area of the donor ingot.
....... in general it caused a lot of nucleation an a "rippled" growth.



next experiment will be with the highest possible purity. (and low voltage, large donor area)



And on a side note:
Sorry for having been absent. I've been overworked due to new job functions (But I'm alive and hope to appear some more in the time to come).

 

[chefjosh77]

A Bit off topic...

If you like Crystals, google "how to make Bismuth Crystals" They are very cool.

 

[metatp]

I am really enjoy my silver cell (thanks Lazersteve). This is the a crystal I made yesterday. I even made one that looked like a horse :lol: .

 

[peter i]

Yup, I've had a lot of crystals growing exactly like that.

They start out with a (often quite long) needle shaped crystal in the middle, and then there is a cubic growth on the sides.

Some examples (sorry for the crappy picture. I only had a webcam handy )
(squares are 5X5mm)

I'd like the crystal to either continue growing like a needle or a cube. The little game they play about sprouting new crystals is what really annoys me!

 

[metatp]

Nice cryatals peteri. I don't know about you, but I always see different imagine from the crystal. I am sure that if you can get one that looks like Mary crying, you could make a fortune. I see you already made a kangaroo (or is that a dinosaur?).

I tried something new this time and got mostly needles. I went to a 2000ml beaker, but I raised the cathode (SS) to about 3 inches from the anode. That left a 2-3 inch gap under the cathode. To my surprise, the crytal started growing a normal, but tipped over and started growing upside down. I already processed about 900g of cemented silver from that batch of electrolyte before I tried this. The electrolyte was already quite blue.

Regards,
Tom

 

[HAuCl4]

Dunno if this will help, but it's a cool video:

http://www.youtube.com/watch?v=l_USYub3djY

 

[peter i]

@ HTPatch: Yes, it is like a crystallographic Rorschach-test. It's hard not to see shapes and pictures in the crystals.
And the crystal growth seems to have a will of it's own (I guess that is what makes it challenging).

@HAuCl4: That is a very cool video! I have considered slowly rotating the acceptor during the growth, but there are some practical challenges that needs addressing to do that. (The synchronous motor from an "Electric Lamp and Appliance Timer" is my prime candidate, and then some kind of brush to make the electrical connection)

 

[METLMASHER]

Fascinating thread, nice work.
It might be a dumb question but have you used evaporation instead of current on the silver nitrate or does that not occur with that solution?
Time and ambient evaporation (if possible) will give a slow growth but might be just as dendritic as before.
Maybe a semi - conductive as a buffer before (or AS) the cathode will drop the current enough to make a 2 pound :shock: crystal. :lol: WOOHOOO :lol:
Let me know, I'd like to try some of these experiments soon as I have a better equipped lab. (Less clutter )
METLMASHER

 

[Harold_V]

Fascinating thread, nice work.
It might be a dumb question but have you used evaporation instead of current on the silver nitrate or does that not occur with that solution?

Evaporation will yield silver nitrate crystals, which are not difficult to grow in the least. What these people are discussing are elemental (electrolytic) silver crystals, which grow under their own terms. I am not aware that evaporation would be useful----it would be no different from raising the amount of silver in solution by other means.

Harold

 

[NewBullion]

Hi. I grew my first silver crystals this week. I used an anode cast from silver I cemented using copper. I harvested 150g initially, for no particular reason besides curiosity. Very white looking bobbly and spindly crystals. Most broke up upon harvesting.Then I allowed the cell to run non stop until the anode had gone, only to change the filter cloths 3/4 of the way through. Only because there was in my opinion, there was alot of sludge, so just to be sure I made the change. I used 8 layers of polypropylene cloth and no sludge was seen on the underside of the cloths. It took approx 48 hours to run 450g+. Cathode was 304 s/steel sheet. Spacing of electrodes was approx 3.75". 2 litre cell with 200g 999 to make the nitrate. 240ml of Nitric and 240ml of H20 to dissolve the pure 200g and filled the rest with H20 until 2l. The second batch had more "fluffy" looking crystals but not as shiney or white as the first batch. More grey in areas than silver and coral looking. I kept the voltage between 3.1v and 3.7v at all times adjusting but most of the time, voltage was set at 3.5v. Current never exceeded 6A, and averaged 0.4A per sq inch of anode area that faces the cathode. Got down to 0.3A running through the cell by the end. Any ideas as to the colour or fuzziness?

Thanks in advance

 

[goldsilverpro]

Ideally, the crystal should be whiter, shinier, and harder. In a perfectly balanced system, which is almost impossible to achieve, you will dissolve about 4 grams/amp-hr at the anode and deposit 4 grams/amp-hr at the cathode. That way, you would have the same amount of silver in the solution at the end that you had at the beginning.

I need more info to make a final judgment, but it seems like the anode was less efficient than the cathode and you therefore removed all or most of the silver from the solution. That could be why the amps tapered off at the end. 8 layers of cloth could be too much and could reduce the anode efficiency.

Please note that this is designed to be a continuous system and not a batch system.

Questions:
(1) What was the average amperage over the time period the cell was operating.
(2) After rinsing and drying all the crystal produced, weigh it. This will give you an idea of how much remains in the solution. There is also probably a little in the sludge but it would be hard to determine how much. I wouldn't worry about that.

I would reduce the amperage to about .25 amps/sq.in. (about 35A/ft²) of anode area (only calculate the area of the side of the anode facing the cathode). Since you didn't add any copper to start with and there wasn't much in the bar, this could be a reason for fluffy crystal. Were it me, I would add about 8g/l to start. That's about 1 tr.oz./gal. I would also reduce the layers of cloth.

 

[Harold_V]

Since you didn't add any copper to start with and there wasn't much in the bar, this could be a reason for fluffy crystal.

I must (respectfully) strongly disagree. I have years of experience processing silver without the addition of copper to the electrolyte. Never, ever, when starting the cell with fresh electrolyte, did I manage to grow anything but robust, hard crystals, the sole exception being when a hard film of silver would develop. That condition was short lived, easing up as copper accumulated. The resulting crystals were hard, but softened as the copper content increased. Towards the end, when the solution was saturated beyond acceptable limits, only then did I grow soft filaments of silver. This entire sequence was predictable and repeated routinely. I'm convinced, beyond a shadow of a doubt, that a small percentage of copper is used to prevent the formation of hard crystals that rigidly attach themselves to the cathode, so I dismiss the notion that the problem was caused by the lack of copper. I have never found a shred of evidence to support the idea.

I would also reduce the layers of cloth.

With that I am likely to agree. My first filter was a very heavy, fine weave of cotton, measuring an honest 3/32" in thickness. It was so heavy and tight that I experienced depletion of the electrolyte.

Harold

 

[wct0415]

Here are some pictures of my latest silver cell crystal growth with experimentation lower voltage and current. The pictures of the crystals were grown in a 24 hour period at .8vdc and current draw was at 1.1 amp average. Unfortunately. when I came home from work the structure had collapsed from the weight of the growth.

I am going to start a new batch of electrolyte with some crystals from this batch since this one has some copper in solution and to what extent I am not sure. One thing I did notice was when this was complete that my cathode was heavily crystallized and and the crystals were somewhat tannish in color . It was so heavily coated that the only way to remove them was to reverse the polarity of the anode and cathode with out the filter and grew more crystals off the anode bar. I likewise only used one layer of polypropylene cloth as my filter. Maybe this is why my cathode has discolored.

Anyway here are my pictures

 

[stihl88]

Very nice solid crystals their WCT!

 

[wct0415]

Very nice solid crystals their WCT!

Thanks! In my current cell I have another quite large crystal of about 3" long with many other 1.5 - 2" off shoots and are getting quite dense. Will post pictures when harvested.

 

[stihl88]

Keep them coming, you could probably have a go at selling them as is on Ebay with a good margin. I'm willing to bet people would snap them up for their elemental collections etc...

Your cell looks like similar dimensions to mine. I'm going to try and grow some of these fat boys myself, just got to resist turning the voltage up so high :twisted:
I'll probably have to play around with my cathode dimensions also.

 

[peter i]

Sorry for having been gone for a while, but I've been playing too!

I had almost given up and had started depleting the cell.

The start concentration was 280g silver/litre.
I cut that in half (took out half the electrolyte and refilled with distilled water), reduced with copper, cast a bar and refined it in the cell.
The voltage was 1.2V and nothing special happened (and the bar tested 99.999 in XRF)
I cut it again (it must be around 70g / litre now), and once the bottom of the cell had been covered, this little darling grew out of the mass:



It is my largest crystal so far, and now I have lot of variables to consider:
- The summer has ended here, and the workshop is approx 15 degrees centigrade (lower temperature should decrease nucleation)
- The concentration is decreased, meaning lower electrical conductivity, and thus lower depositing in the receiving end
- lower depositing also means lower supersaturation, and thus less nucleation
- the crystal grew from a large lawn of crystals, and the silver was donated from a relatively small bar. This makes it slower too.
- there is quite a bit of copper in the electrolyte, wonder what that does?

I've restarted with a rod of silver sinking into the basket (rather than a massive bar), 1.2V and the same electrolyte.
I'm exited to see what will happen!