Twospoons
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Growing a CuSO4 crystal using a "hydrothermal" process
I thought I'd have a crack at growing a copper sulfate crystal using a setup based on hydrothermal crystal growing methods. Obviously I don't need
high pressures or temperatures for CuSO4, so I built a simple setup using a 2000ml measuring cylinder and a cheap Chinese coffee cup warmer (~20W).
This is really just a proof of concept - no attempt has been made to optimize the process.
Initial setup:
1: A 2000ml measuring cylinder, with its plastic base removed, is placed on a heating plate (coffee cup warmer). I used a lab stand for extra
stability as I have a kitten whose middle name is "trouble".
2: 1800ml of saturated CuSO4 solution @50C is added, along with 200g of solid CuSO4.
3: The bottom 1/4 of the cylinder is wrapped in insulation, a cover is added, and the heater is turned on.
4: The system is left to equilibriate for several days.
5: A small seed crystal is suspended in the top 1/4 of the cylinder.
My initial seed was about 9mm long. After 3 days it is already significantly bigger. I don't want to disturb the process by pull it out and measuring
it so I'm trying to take pics through the cylinder.
At any rate, it looks like the process is working. It has a couple of nice advantages: Its sealed so there's no water loss, so no need to top up. And
condensation at the top is continually washing the glass so there's no crust growing up the sides.
The photos are of the initial seed, then 3 days later. The last photo shows my setup (with the insulation pulled aside to show the heater and solid
CuSO4)
  
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Ubya
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very intresting
a few weeks ago i was thinking to use the same process to make sulphur crystals from a saturated solution of toluene and sulphur, if it worked with
CuSO4 i will definitely give it a shot
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Twospoons
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The crystal is now ~40mm long. I'd post a pic, but unfortunately my phone turned into a brick yesterday.
I don't see why this wouldn't work with toluene - and it has the added bonus of no toluene vapor to get rid of.
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elementcollector1
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Now if only there was a low-pressure hydrothermal method of growing quartz... I'd be all over that.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Twospoons
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Yesterday I turned off the heater, as prep for terminating the experiment. This was a mistake - the crystal grew fast overnight, and at some point the
suspension broke and it landed in the solid mess at the bottom. Result was not pretty. It did weigh 90g though - this is after 19 days growth.
I had noticed a missing corner on the crystal earlier - I think this was due to a less than perfect seed. Going to try again with a better seed. This
is definitely a fairly quick way to grow large crystals.
My phone died last week, so no pic of the result sorry.
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Ubya
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Quote: Originally posted by Twospoons  | | at some point the suspension broke and it landed in the solid mess at the bottom. Result was not pretty. It did weigh 90g though - this is after 19
days growth. |
that's unfortunate
anyway, wow 90g!
i need to find a coffee mug heater and try it, bad news is that in italy they are not something common to find so probably i need to go to my trusty
ebay and wait 1 month for a shipment from china...
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Twospoons
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I got my heater from china - on Aliexpress. I've bought quite a lot of stuff that way, and only encountered issues a couple of times.
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Twospoons
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Second attempt. This took about a week and a half to grow to this size. It has unfortunately sprouted a twin on one side.
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Ubya
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| Quote: Originally posted by Twospoons | Second attempt. This took about a week and a half to grow to this size. It has unfortunately sprouted a twin on one side.
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pretty damn fast.
what is the temperature in the hot and cold sides?
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Twospoons
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At the top, and in fact most of the way down, its 34C. Right at the bottom, on top of the bulk CuSO4, its 42C.
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blogfast25
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I'm trying to set up a similar experiment.
How did you measure the temperature of the hot zone?
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Twospoons
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I just stuck a thermocouple into cylinder, briefly.
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blogfast25
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I've water-proofed a thermocouple but I'm getting low temperatures (< 30 C) at the bottom. Need more patience, I guess...
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Twospoons
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As I recall it took a while for the temperature profile to establish and stabilise, by which I mean many hours. Insulation around the bottom helps,
as does having a stable room temperature.
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blogfast25
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I'm using a 1 litre measuring cylinder with the base stands cut off and the bottom quarter insulated with expandec LDPE. I use an old hot plate on a
very low setting.
I'm getting about 45 C at the bottom, so great, right? Trouble is that the top temperature is only 2 - 3 degrees lower...
Looks like I need myself some cooling fins! 
[Edited on 16-3-2023 by blogfast25]
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Twospoons
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I honestly dont know how much delta T is needed for this to work - probably depends a lot on the solubility vs T curve. And will be limited by how far
you can go into super-saturation before stuff just spontaneously crystalizes.
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Fulmen
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Your approach is a bit one-sided. Yes, for rapid crystal growth you want a large dT, but this also increases the risk of defects. The slower you grow
the crystals the better it will be. So the real answer is "it depends on your setup" and requires some patience on your behalf.
Although measurements are useful the most important thing here will be repeatability and stability. The setup should be well defined and done in a
temperature controlled environment. The heat source can be any stable (resistive) load like a heating element or light bulb. I would avoid regulated
heat sources (at least initially) as they could induce switching fluctuations.
We're not banging rocks together here. We know how to put a man back together.
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blogfast25
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| Quote: Originally posted by Fulmen | Your approach is a bit one-sided. Yes, for rapid crystal growth you want a large dT, but this also increases the risk of defects. The slower you grow
the crystals the better it will be. So the real answer is "it depends on your setup" and requires some patience on your behalf.
Although measurements are useful the most important thing here will be repeatability and stability. The setup should be well defined and done in a
temperature controlled environment. The heat source can be any stable (resistive) load like a heating element or light bulb. I would avoid regulated
heat sources (at least initially) as they could induce switching fluctuations. |
Agreed with everything, especially your openiing sentence.
But "I would avoid regulated heat sources [...]" probably isn't a measurable effect because of the thermal inertia of the solution column.
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Texium
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Thread Moved
30-11-2023 at 10:55 |
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