Sciencemadness Discussion Board

Crystal Growing

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lacrima97 - 21-3-2006 at 06:42

I saw something about this a while ago, and I remember my dad helping me grow this blue crystal when I was little, but how does it work? How could you grow, maybe a CuSO4*H2O for example. How are they actually formed to look so pretty? Is it simply dissolving the substance in a solvent, and then evaporating the solvent?

kazaa81 - 21-3-2006 at 07:49

Copper Sulphate Pentahydrate
CuSO4 * 5 H2O
CAS #: 7758-99-8
Mol. 249.686 g/mol
Form: blue tricline crystals
M.P. 110°C decomposition
Density 2.286 g/cm^3
Soluble 22.0^25 g in 100ml H2O
Soluble in MeOH, slightly soluble in EtOH

(from CRC press, handbook of chemistry and physics, 85th edition)

Work out of this

DrP - 21-3-2006 at 07:58


How are they actually formed to look so pretty? Is it simply dissolving the substance in a solvent, and then evaporating the solvent?

This will give you lots of very tiny ones. To get a nice big pretty one you should select the biggest of your small ones to use as a seed. Hang this seed into a saturated solution of the CuSO4 by a piece of cotton and it will grow! (you can use a lolly stick to hang the cotton from over the top of a beaker). This may take some practice and some time to get nice big ones... :)

12AX7 - 21-3-2006 at 12:52

How do you get it without the string embedded? (What's that do to purity, strictly speaking? LOL)

I've had a few reasonable results with placing a seed crystal in the bottom of a container and evaporating slowly. However, you have to clean it off periodically as smaller crystals will settle into place and intersect, and any movement (of the solution) or contact with the crystal tends to upset growth.

Does anyone have a library of crystal habits? That would be as useful as chemical properties in identifying isolated substances.


lacrima97 - 21-3-2006 at 15:49

Ah, I see, so just have a crystal for the others to attach to...Hmm, I might give this a try sometime.

bereal511 - 21-3-2006 at 18:15

I found this site to be quite interesting and helpful in making large, single crystals.

NeutralIon - 21-3-2006 at 18:29

I did some crystal growing years ago when I was in high school -- kind of a extra credit chemistry project -- in fact my chem teacher gave me the chemicals to grow the crystals from.

DrP's comment about hanging a seed crystal on a string is correct -- that will give large, well shaped crystals. Basically you create a saturated solution in boiling water, then let the solution cool to become super-saturated. Then carefully lower the seed crystal into the solution and let everything set undisturbed. If it don't work out right press reset -- i.e. just boil again to get everything disolved and start over.

A very good substance to start with is alum, KAl(SO4)2.12H20. This is one of the easier to grow and makes beautiful, clear octahedral crystals. Chrome alum, KCr(SO4)2.12H20 is another good one -- it makes deep violet octrahedral crystals. I did both of these those many years ago.

For a really neat effect you can even grow a chrome alum crystal and use it as a seed to grow a clear alum crystal over it -- one of the few cases where a crystal will grow well on a substance other than itself. This leaves you with a perfect violet octahedron inbedded in the center of a clear one. I never got the chance to try that but I have seen pictures.

The_Davster - 21-3-2006 at 18:55

I too did some crystal growing in my time, by the same method mentioned above. I used potassium sodium tartrate. Attached is a picture of the crystal which I dug up out of the lab.

crystal.JPG - 24kB

Crystal growing

MadHatter - 22-3-2006 at 02:30

Lacrima97, check your U2U for FTP access. There is an article there by Peter G. Jones that
may help you.

kazaa81 - 22-3-2006 at 05:40

I think that melting the salt and then let it cool slowly is a good method to grow large crystals

12AX7 - 22-3-2006 at 07:13

Has to be pure though (impurities prevent the liquid phase from orienting to the crystal, or even nucleate other crystal growth), and done very carefully, since the melting point is sharp.

With some servos (for crystal pulling) and a temperature feedback system, I *might* be able to do something like that with my induction heater, when I get it up to power.


JustMe - 22-3-2006 at 19:17

Neat site, bereal511.

I've done some crystal growing a long time ago. Evaporation technique/cooling technique depending on the substance. Spent six months growing ammonium alum crystal. Grown Copper Sulphate hydrate, potassium dichromate.

Yes, the trick is to get a seed crystal, and then, for even growth, carefully turning them on a regular schedule so that all sides have equal access to the solution.

But when I was doing my old science fair project and growing crystals of transitional metal saccharin compounds I did something unusual. Most of the compounds were soluble in water, but sparingly so (except for copper) in acetone. For example, I would make a solution of Zinc Saccharin in water, add acetone until it just started to come out of solution, then warm the mixture enough so that it redissolved. Instant saturated solution. On slow cooling I got some pretty spectacular crystals (meaning up to a quarter inch).

The slow evaporation method worked well for most of the other compounds, but this was the only way I got good crystals for zinc saccharin.

By the way, I've had a salt crystal growing for more than 30 years! I was in Israel 30 years ago and got a sample of dead sea water and put it into a small jar. I noticed over the years that a crystal formed on the bottom and the volume decreased ever so little... obviously an imperfect seal. So I carefully shake it to turn it over every few years. Now it is like a ship in a bottle (small neck), but there is still plenty of solution left. I just checked, it is about an inch square, 1/4 inch thick and the bottle is about half empty (Probably held only about 3 oz when full.) 30+ years I've had that puppy, tempted to break the bottle to pull it out... nah, just let it go another few years.

hodges - 22-3-2006 at 19:47

Here is another interesting kind of crystal to grow:

unionised - 23-3-2006 at 12:29

"For a really neat effect you can even grow a chrome alum crystal and use it as a seed to grow a clear alum crystal over it -- one of the few cases where a crystal will grow well on a substance other than itself. This leaves you with a perfect violet octahedron inbedded in the center of a clear one. I never got the chance to try that but I have seen pictures. "
I have done it. Not only that but, if you use shallow trays of the solutions you can grow"rings" of crystals. Grow a small Crhome alum xtal, put it in a tray with staurated aulm and let that grow a layer round the seed. If you only use a shallow layer of solution the crystals grow wider but not a lot thicker. Then you can do the same thing with a dish of chrome alum and get a purple ring and so on.
You can also mix chrome alum with ordinary alum and get a range of colours from near black through violets and amathyst to white. Great fun as I recall.

Barium chloride

MadHatter - 24-3-2006 at 10:37

I made barium chloride with the carbonate and HCl and sat the mixture off to the side.
I had forgotten about because of other projects. The water evaporated in the course
of a month and made some beautiful crystals that looked like glass in the jar.

Magpie - 24-3-2006 at 11:35

I just finished making a batch of Ba(OH)2*8H2O crystals. They are nice looking glassine flakes which I dried to dampness using a Buchner funnel sealed to a source of purified air. I'm not going to try to get them any drier as I don't have the required dessicant or a vacuum dessicator.

[Edited on 24-3-2006 by Magpie]

[Edited on 24-3-2006 by Magpie]

Ashendale - 26-3-2006 at 05:57

I also tried to grow crystals, took 55 grams of CuSO4 * 5H2O and 100ml of water, heated until all CuSO4 had dissolved and then let it cool.
In the morning I found beautiful CuSO4 * 5H2O crystals on the bottom óf my beaker :)

I'll include some pictures (sorry for the quality)

EbC: --> Attachment reduced to allow inline viewing...

[Edited on 14-9-2006 by chemoleo]

PHTO0009.JPG - 58kB

Vol 2

Ashendale - 26-3-2006 at 05:58

(How do you add multiple files to one post? :S)

[Edited on 26-3-2006 by Ashendale]

EbC: As above.

[Edited on 14-9-2006 by chemoleo]

PHTO0010.JPG - 41kB

chemoleo - 26-3-2006 at 08:51

Ok, time to show off a little :D

The crystals below are CuSO4 of course, and I have four of them, weighing 1.3 kg each, roughly 20 cm long. They have been growing for 2 years, with the evaporation method. It was a fair bit of work, because the solution had to be filtered frequently (dust, mold), and topped up, while the growth vessel had to be cleaned out regularly. I grew them in a 10 l bucket (yes with 10 l of CuSO4 solution), because the smaller cups/pots I started off with became progressively too small. Currently they aren't growing, put I might pick it up at a later time. The 2nd/3rd crystal are a bit rough on the right edge, because the last time round it evaporated onto the crystal level, making it all mingy and producing this turquoise amorphous stuff. This is not a problem though, I will scrape it off with a knife, wash it with dH2O a bit, to regrow it in CuSO4 once more. Another problem was the nylon thread I used initially - it was too thin and too weak, so the weight eventually ripped it. The current nylon thread takes 9kg, so I still have some leeway. But if you plan big crystals, use the stronger thread from the start, because fixing it later onto a grown smooth crystal (such as the first one) is very difficult, in fact I had to saw into edges a little to fixate the thread. Again, no problem if it is cleaned nicely after that, and regrown. Sadly the quality of the crystal suffered a little from it. However, if you grow it long enough, the crystal layers become so dense you can't ever see the fault.
Other than that, they are the proudest pieces of my collection!

Mephisto upped those pictures on LambdaSyn, with more details given there (German).

Darkblade48 - 26-3-2006 at 12:17

:o 1.3 kg! Each!!!!

Those are pretty impressive chemoleo, though I don't think I have any plans for getting a 10 L bucket to grow crystals in just yet :)

garage chemist - 26-3-2006 at 15:18

Those crystals are truly enormous. I have never seen something like that produced by a non- commercial crystalgrower.

Research has really mastered the technique of crystal growing though... I once saw a picture of a 320kg crystal of potassium dihydrogen phosphate. They used a special apparatus, with continuous dissolving of fresh material and circulation of the solution, together with an elaborate system of heaters, coolers and pumps to constantly create a very slightly oversaturated solution in the tank.

Those are normally cut into thin slices and used for lasers, for shifting wavelengths.

With the interest in crystalgrowing here, I just started a small batch of CuSO4. 40g CuSO4 Pentahydrate in 50ml water, heated until dissolution and left to stand covered overnight. I'll see what has formed in there by tomorrow.

I'm interested in growing crystals with unusual materials.
I'll try to create single rhombic crystals of sulfur, by very slow cooling of a saturated solution of sulfur in hot toluene (the evaporation method is not appropriate here, because the solubility of sulfur in toluene at room temperature is too low).

Alternatively, I could use CS2 and the evaporation method (though that would have to be done outside due to toxicity).
The evaporation would have to be slowed down by a cover over the beaker, the CS2 would evaporate too fast otherwise.

I also poured some 45% NaClO3 solution (of which I have several liters) into a shallow plastic dish (evaporation method), because I read that NaClO3 can also be used for growing crystals.

A really cool thing would be to hydrothermally grow crystals of quartz.
SiO2 is quite soluble in water at temperatures around 300°C, and therefore crystals can be grown in an autoclave.

chemoleo - 26-3-2006 at 17:07

Well thank you. Very interesting what you mention on quartz crystals, I have one sitting right on top of my computer screen, and I always wondered under what conditions it might have formed. I alwyas thought it was formed by melting and cooling, but never could explain why it would, for instance, sit in those globular rock balls - which are cut apart and contain lots of quartz crystals. Now I know - who would have thought SiO2 is soluble in water at 300 deg C ?:o I gotta get one heavy duty autoclave! Do you have more information on SiO2 crystals, i.e. how they are made commerically?

As to the KH2PO4 crystals - I actually saved an article on this from the BBC website, published 15th Feb 2000:

Lab grows monster crystal

It measures 66 (cm) by 53 by 58.

If you ever struggled to grow copper sulphate crystals in a jam jar at school, look enviously at this monster.

The pyramid-shaped KDP (potassium dihydrogen phosphate) crystal is a record breaker. It weighs in at an astonishing 318 kilograms (701 lbs) - more than 20 kilos heavier than the previous record holder.

It was grown in just 52 days by researchers at the US Department of Energy's Lawrence Livermore National Laboratory, California.

The enormous crystal is to be sliced into plates for use in a giant laser now under construction at Lawrence Livermore. The crystal plates will convert the laser's infrared light beams to ultraviolet light just before the beams strike the laser target.

The new equipment will test the safety and reliability of America's nuclear weapons stockpile.

The growth technique builds on Russian methods.

Russian technique

To grow crystals this big, Lawrence Livermore built on a rapid-growth technique first developed in Russia.

A thumbnail-sized seed crystal is placed inside a two-metre-high tank filled with nearly a tonne of supersaturated KDP solution at 65 degrees Celsius (150 degrees Fahrenheit).

The temperature is gradually decreased to maintain supersaturation as the growing crystal extracts salt from the solution.

The record size of the latest crystal was achieved by giving the solution a transfusion of additional salt through a device called a continuous filtration system, which helps maintain crystal quality.

"This technique offers the possibility of producing even larger and higher quality crystals in the future," said Ruth Hawley-Fedder, group leader for the Livermore crystal growing team.

"Our newest record holder could have grown even larger, but we simply ran out of room in our growth tank."
Images by Jackie McBride and Bryan Quintard, Lawrence Livermore National Laboratory

What I don't quite understand about this technique is how they keep the crystal afloat, there doesn't appear to be a fat nylon cable suspending the crystal. I almost suspect they just place a nice seed crystal at the bottom of the vat, flat side down, and just let it grow. I don't know the crystal space group of KH2PO4, but possibly the bottom side of the crystal isn't what the natural crystal would look like.

[Edited on 27-3-2006 by chemoleo]

lacrima97 - 28-3-2006 at 06:01

Very Very nice chemoleo, thank you for the inspiration, I will most definately be attempting this project myself, :D

unionised - 28-3-2006 at 12:22

Not as big as some natural crystals but very impressive, and the clarity...
NaClO3 IIRC forms crystals that are chiral (there are left and right handed versions).
Crystals of NaNO3 act like iceland spar and split an image in two.

garage chemist - 28-3-2006 at 13:53

Here is a nice description of the hydrothermal growth process for quartz crystals.

Note how the "Low Pressure Process" uses "only" 700- 1000 bar. :o

My attempt at growing large sulfur crystals failed.
At first, only monoclinic crystals were formed, very long and very thin needles.
I read up and it found that at temperatures of about 95°C, only the monoclinic form of sulfur is stable.
So I added more toluene (a total of 65ml for 6g sulfur) to lower the temperature at which sulfur begins to crystallise, and also 1ml of CS2 (I know that slow evaporation of a CS2 solution of sulfur makes rhombic crystals, so I thought that a small amount of CS2 could favor rhombic shape).
I used a water bath to heat the hermetically sealed vessel, and let it cool down in the covered water bath (the water bath serves as thermal ballast to slow down the cooling).

It actually makes rhombic crystals now, but they are small and there are a lot of them. They also have this very strange behavior to grow into needles with the rhombic crystals on them like a string of pearls.
The individual crystals are very good though, a pure yellow and absolutely clear. They also redissolve very slowly, even when the toluene is hot enough to allow complete dissolution.

The crystalline sulfur would look great as an element sample, much nicer than the powder one always sees.

Sandmeyer - 22-4-2006 at 17:45

Good work chemoleo, that's really hell of a crystall!

mrjeffy321 - 23-4-2006 at 10:10

chemoleo's crystals are quite impressive. At first, I didnt notice the coin, once I did, WOW.

Copper (II) Chloride works pretty well for growing crystals too.
I made some CuCl2 once and left it in a pan to dry. I forgot about it for a month and when I came back, it had formed into green and blue (Hydrated I assume) crystals on the sides and bottom of the container.
Had I been trying to make crystals and put a seed in there to start, I probably could have gotton something pretty good.

CuCl2_Crystals.jpg - 63kB

12AX7 - 23-4-2006 at 10:59

CuCl2 sucks for crystallization, it makes those acicular mats of crystals :rolleyes:

[How come we *still* don't have a rolleyes smiley?]

That's an interesting bed of crystals though :)

I've got a salt that makes large crystals easily, I have no idea what it is, it seperated from my failed urea fermentation experiement. When I grow a big crystal I'll take a picture...


DrP - 25-4-2006 at 05:22

OK, I've got some CuCl and was going to try crystal growing with it but probably wont bother now - may still try anway.

12AX7 - check out the smilies they have available at

there are some funny ones.

12AX7 - 27-8-2006 at 11:47

Speaking of CuCl2-- I think I've discovered that a strong HCl solution (enough for a burning odor, probably 10-20%) grows crystals better than impurities having anything to do with it.

Might I hazard a guess that the common ion effect reduces solubility, allowing crystals to organize better?


Bromine - 7-9-2006 at 12:28

What about copper(II) acetate, it is ok for makign large crystals?

woelen - 7-9-2006 at 13:31

Originally posted by 12AX7
Speaking of CuCl2-- I think I've discovered that a strong HCl solution (enough for a burning odor, probably 10-20%) grows crystals better than impurities having anything to do with it.

Might I hazard a guess that the common ion effect reduces solubility, allowing crystals to organize better?


No, CuCl2 actually dissolves better in very concentrated HCl than it water. This is due to complex formation. A yellow/brown complex is formed, most likely CuCl4(2-), but probably also HCuCl4(-) and H2CuCl4. The crystals, obtained by crystallization from HCl contain a lot of acid, and they also have a different color than pure CuCl2.2H2O. The pure salt is cyan/blue, the stuff, obtained from HCl to my experience is much more green with a yellow tinge. Below follows a picture of CuCl2.2H2O.

[Edited on 7-9-06 by woelen]

12AX7 - 7-9-2006 at 14:09

Ya, about the same as my stuff (see my copper salts page).

The stuff I get is certainly green when moist, but I always attributed that to solution, which is certainly going to stick well (capillary action) given the nature of the hairy crystal blooms.

Well I crystallized some more just today, check it out for yourself.

(Second is sideways and upside-down view of same.)

Most of the liquor has been poured off, which means there's plenty still stuck inside the growth, which has to be broken up and squeezed in filter paper (vacuum would be better!). The liquor is definetly thick deep green, with only a tinge of yellowness. It looks yellower on soaked paper towel, but I would like to think that's due to stuff in the paper oxidizing (copper shouldn't affect cellulose much in that way, though).

Your product may be a bit bluer than mine, lemme see... eh the contents of this jar (now much more than just the little bottle shown on my site) is definetly not as dramatically blue as yours. On opening it smells strongly acidic, not of any particular odor (except the odor that wasn't well cleaned from the jar before I got it). Maybe I'll dry it out a bit more...


[Edited on 9-7-2006 by 12AX7]

12AX7 - 13-9-2006 at 17:21

I'm growing (recrystallizing I should say) some ammonium sulfate lately. This is one byproduct of the first urea fermentation thing, that didn't do anything; as the urea hydrolyzed I added sulfuric and hydrochloric acids to neutralize pH.

When I dissolved the stuff in tap water, nothing happened. I filtered the solution and evaporated it down until it started crystallizing. After stirring, causing a hard mat of fine crystals to precipitate, I filtered and redissolved the material. This left a small amount of small transparent acicular crystals, approximately several mm in length and evidently low solubility.

Yep... you know it, calcium strikes again!

Just an FYI, and I suppose the possibility of growing gypsum var. selenite crystals, small ones at least, at home.

(Oh and as for the (NH4)2SO4, I have some blocky, misshapen, clear to milky, colorless crystals on hand, soon to be more.)


Giant gypsum crystals the size of trees!

chemoleo - 11-4-2007 at 15:17

Now I just wish I had some of these! Look at the size of the person!

They just recently worked out how such big crystals could form naturally. Check,1518,476553, for the Germans here.

In a nutshell, this is 300 m below ground, found through mining, in a grotto in Mexico, the Chihuahua desert (Naica).
Up to millions of years, 54 deg hot water filled this grotto, depositing CaSO4*2H2O, and the temp must have been extremely stable otherwise the crystals couldnt have grown (i.e. the anhydride ones would have formed instead). The crystals are now in the dry becuase groundwater is pumped away for mining. As soon as the pumps stop, the crystals will start growing again!
For reference, the biggest such crystal made in a lab measures 2 cm in length! If one of these crystals is 10 m long, and say that it takes 1 cm/year for growth (which is likely an overestimate), then they would have been growing at least 10000 years!

Darn I'd love to have one of these in my house!

The original article from the journal 'Geology' is here


Title: Formation of natural gypsum megacrystals in Naica, Mexico
Abstract:Exploration in the Naica mine (Chihuahua, Mexico) recently unveiled several caves containing giant, faceted, and transparent single crystals of gypsum (CaSO4•2H2O) as long as 11 m. These large crystals form at very low supersaturation. The problem is to explain how proper geochemical conditions can be sustained for a long time without large fluctuations that would trigger substantial nucleation. Fluid inclusion analyses show that the crystals grew from low-salinity solutions at a temperature of ∼54 °C, slightly below the one at which the solubility of anhydrite equals that of gypsum. Sulfur and oxygen isotopic compositions of gypsum crystals are compatible with growth from solutions resulting from dissolution of anhydrite previously precipitated during late hydrothermal mineralization, suggesting that these megacrystals formed by a self-feeding mechanism driven by a solution-mediated, anhydrite-gypsum phase transition. Nucleation kinetics calculations based on laboratory data show that this mechanism can account for the formation of these giant crystals, yet only when operating within the very narrow range of temperature identified by our fluid inclusion study. These singular conditions create a mineral wonderland, a site of scientific interest, and an extraordinary phenomenon worthy of preservation.

[Edited on 11-4-2007 by chemoleo]

unionised - 14-4-2007 at 08:27

I may be getting cynical in my old age but that's the April issue of that journal and I have never seen a cave that well lit. I suspect shotoshop.

chemoleo - 14-4-2007 at 09:35

Nono... lol what are you on about?. Obviously they put big lights in there, for the photoshots. You can see certainly crystal faces in the dark spots being bright, indicating a specific light source.

The_Davster - 14-4-2007 at 22:25

Those are amazing! I bet its closed and no tours though:(. I would love to see them in person.

I can't imagine they wouldent use as much fancy lighting as possible for something like that!

unionised - 16-4-2007 at 10:15

OK, I admit I was being paranoid; there are enough references on the web to thoses mines that I believe them.
On the other hand I have taken photographs in caves and it's difficult. I'm doubly impressed.

YT2095 - 17-4-2007 at 01:02

here`s some Copper Chloride I made a while back, it looks more like Woelens than the other Green/yellow sorts?

all I used was Copper Carbonate in HCl (20%).

not_important - 17-4-2007 at 01:21

Originally posted by YT2095
here`s some Copper Chloride I made a while back, it looks more like Woelens than the other Green/yellow sorts?

It comes back to having excess HCl or not, which forms the yello-green complex, and having it good and dry, as strong solutions of CuCl2 are brown-green so a thin film of moisture hides the blue colour.

YT2095 - 17-4-2007 at 01:43

Originally posted by Bromine
What about copper(II) acetate, it is ok for makign large crystals?

it`s not bad at all actually, here`s some pics of the copper acetate I made a while back.

being such a Dark crystal it`s hard to do them justice in a photo using a cheap cam, but if you notice the odd shiny bit, that`s a crystal face reflecting window light, the crystals are Beautiful up close too.

12AX7 - 17-4-2007 at 08:33

Izzat kinda like KMnO4 (dark-ass colored), but blue instead?


Bromine - 17-4-2007 at 08:35

I tried to do some before, i got crystals like on your picture. They look nice to me.

YT2095 - 17-4-2007 at 10:24

Originally posted by 12AX7
Izzat kinda like KMnO4 (dark-ass colored), but blue instead?


naah, these are more a Mega deep Emerald green towards Black.
powdered or scratched they`re Emerald green, whole they`re Black to look at.
and potassium Permanganate when In large crystals would be a good analogy, they too can look almost black when perfect :)

dedalus - 19-4-2007 at 16:17

For ease of growing, you can't beat sodium potassium tartrate.

Once, I got a huge bag, cause it was contaminated w/ NH3 and useless for making the ammonia analysis buffer they used it for. I'm just messing around, not serious at all. I poured it in some tap water, mixed it well, poured the saturated sol'n off the excess. Then, I took a bit of that and made a seed crystal, tied a thread around it...etc. I covered the whole thing with cheesecloth, forgot about it.

I go back to check it a few weeks later, and...OH MY GOD! I'd grown a crystal about the size of a golf ball.

Crystal Growing

ssdd - 22-6-2007 at 02:50

I found a interesting site last night on crystal growing.

It is

I am trying some of the ones he has listed on there now, I'll post my results.

I have also done some work with rapid/slow cooling of Potassium Nitrate saturated solutions.

Also last night I tried rapid cooling of a saturated salt solution with some neat effects.

Anyone else done any work with this kind of stuff?


DrP - 22-6-2007 at 05:11

Yea - check this out! Particularly chemoleo's copper sulphate!

Chemophiliac - 26-6-2007 at 06:07

Has anyone here grown any crystals of more unusual compounds? I'm really interested in crystal growing and although I haven't mastered it exactly, I'm interested in what other people are doing. Personally, I would do anything for a large, perfectly formed crystal of UO2(NO3)2*nH2O (I'm not sure of the hydration number). I also understand that rare earth sulfates and chlorides make for very good crystal growing compounds.

The_Davster - 26-6-2007 at 15:30

At work I accidently grew a crystal 1cm x 1cm x 5mm of bromoadamantane. Thats what I get for leaving my waste in a beaker evaporating because I was too lazy to empty the full organic waste bucket:P.

I will post a pic tomorrow, it adopts a form similar to how bismuth crystallizes, but colorless.

Favorite Crystal Growing Chemicals

Ioxoi - 18-2-2008 at 16:56

Hi everyone,

I was just wondering what everyone's favorite crystal growing chemical was. Some people like the alums; others like monoammonium phosphate, copper sulfate or even sugars.

I'm posting this because I've got a new favorite: triethanolamine hydrochloride! I'm not a "pro crystal grower" (if that title even exists) by any means, but I think some of the really good ones out there should experiment with this chem and see what kinds of results they can get. I've pulled out some absolutely fantastic crystals out of some waste solution growing in one of my mom's plates that put crystals of other chemicals I've purposely tried to grow to shame.

As far as I've been able to tell, the most basic crystal shape (single crystal) is like the right angle prisms found in binoculars. I have one flawless crystal (it has a small internal striation, though) and when you look at it up close, it's unbelievable how perfectly smooth it's shape is. It actually looks like an acrylic prism from a precision optical device, except shrunk down to a couple mm on a side! I've also gotten some bigger clusters, but again they were growing in a dish unintentionally so I'm sure other guy out there could get much better results.

The main reason I like them better than others is
1. They're perfectly clear and
2. They're really stable. They don't dehydrate and turn opaque and they don't liquefy in humid air as far as I've been able to tell. I don't think they even form a hydrate at all.

You can make it in mass by buying a gallon of TEA from the and then adding a big excess of muriatic acid. You can filter and dry the crystals (careful, heat makes solution outgas HCl) or just dilute the slurry down until it dissolves and use that as a crystal solution.

Anyone got any other favorites?

Nick F - 19-2-2008 at 05:10

I haven't tried it yet, but I'm going to try putting a sat. cobalt chloride solution into a vacuum desiccator. I hope that this will speed up crystal formation, while still making it slow enough for nice crystals to form. I just really love the colour of that compound! Then I'll probably seal it in something to keep it stable (maybe even cast it in some crystal-clear acrylic resin that I have to make a nice paperweight!).
Large potassium dichromate crystals are beautiful too, but apparenly they're not very easy to grow. And some lanthanide sulphates have nice colours.

12AX7 - 19-2-2008 at 08:46

Incidentially, sodium bromate hydrate (monohydrate I believe) typically forms platelike crystals, reminiscient of BaCl2.2H2O and mica. Unfortunately they are air sensitive (turning white in this dry winter air).

It also forms thin crystals, probably the same habit but finer, when a boiling-hot solution is cooled with few nucleation sites. I had hot filtered a solution, half a day later discovering that it had congealed into a radiant suspension. Fortunately, such a suspension is easy to break up, because sodium bromate appears to have a relatively small solubility difference with temperature (indeed, a saturated solution at 15C is quite concentrated).


Magpie - 16-4-2008 at 12:23

Earlier in this thread YT2095 shows nice pictures of copper acetate he made. I presume this is cupric acetate.

I am attempting to make same, but I think my synthesis is going bad and I'm getting Cu(OH)2 instead. Here's what I did:

I reacted stoichiometric amounts of of Ca(OH)2 and white vinegar (5% HOAc) to form Ca(OAc)2 in lots of water. Then I added a stoichiometric amount of CuSO4*5H2O.

Ca(OAc)2 + CuSO4*5H2O --> Cu(OAc)2 + CaSO4*2H20 +3H2O

The gypsum was then removed by filtration, which is not hard when using a little diatomaceous earth added and a Buchner funnel.

Then I placed this navy blue translucent solution, which I assume to be aqueous Cu(OAc)2, on a hotplate-stirrer to evaporate off the water. But, it turned into a light blue slurry upon heating and vapors smell strongly of acetic acid. Hence my assumption that I'm forming a Cu(OH)2 slurry out of my dilute Cu(OAc)2. Right?

Now my question for YT2095: How please did you make your nice dark green crystals? :o

And, if anyone else can offer a method for making the Cu(OAc)2 please do. I searched but could not find one.

UnintentionalChaos - 16-4-2008 at 14:21

Why even bother with the messy calcium step? Use dilute NaOH and make Cu(OH)2 (carbonate, bicarbonate (some carbonato complex will exist solvated no matter what so don't expect the liquid to go colorless) or even very slow careful addition of ammonia, stopping when the ppt. begins redissolving as dark blue tetraamminecopper (II) ions) from your CuSO4, filter out and wash the ppt. then dissolve in HOAc. Boil down, with an excess of acetic acid until the solution is intensely dark blue and chill down as much as possible without freezing and keep it there for a few hours (It doesn't mind hanging out supersaturated while crystals slowly form), collect crystals, then boil down again (I found a little more than halving the remaining solution worked out well.

Your slurry is likely calcium sulfate which has a nasty habit of easily forming supersaturated solutions and slowly crystallizing out (happened when I did an analagous procedure using CuSO4 and CaCl2). The boiling probably agitated it enough to force at least some of it to crystallize out.

garage chemist - 16-4-2008 at 14:45

Or even better, use CuO for reaction with the acetic acid- it's way easier to filter than Cu(OH)2 and has a stochiometric composition and no water of hydration.
Just heat the Cu(OH)2 suspension from CuSO4 and NaOH until completely black and the CuO begins to settle.

I thought you had some pure acetic acid by now, Magpie? Why are you using vinegar?

Magpie - 16-4-2008 at 14:57

GC, that method looks very straight forward.


I thought you had some pure acetic acid by now, Magpie? Why are you using vinegar?

Because I am a skinflint. :D

And thanks Un. Chaos for the insight on the CaSO4 formation. I guess that batch is toast. :(

Maybe not toast. I turned off heat, let it cool, then turned off stirrer. White solids (CaSO4) quickly settled out leaving a dark blue translucent supernate with no apparent Cu(OH)2 ppt gel. pH is slightly acid. So maybe some Cu(OAc)2 is recoverable here. I will filter again and go from there.

[Edited on 16-4-2008 by Magpie]

[Edited on 16-4-2008 by Magpie]

[Edited on 16-4-2008 by Magpie]

chemoleo - 16-4-2008 at 16:28

I'm posting this because I've got a new favorite: triethanolamine hydrochloride! I'm not a "pro crystal grower" (if that title even exists) by any means, but I think some of the really good ones out there should experiment with this chem and see what kinds of results they can get. I've pulled out some absolutely fantastic crystals out of some waste solution growing in one of my mom's plates that put crystals of other chemicals I've purposely tried to grow to shame.

Just now I wanted to write, triethylamine HCl doesn't crystallise well (as I've found that it forms needles which are very hygroscopic) and dang, there it is, you are writing on triETHANOLamine HCl :(
Where did you get the triethanolamine from?

On the matter of CuAc2 - I've made liters of the stuff using this very method, with CaSO4 - CaCO3 was dissolved in 25% HAc until it would dissolve no more, and to this the calculated amount of CuSO4 was added. This was filtered, rinsed more with cold H2O until the CaSO4 on the filter went pale green blue. The supersaturated solution started crystallising finest CuAc2 in no time, as glittering dark green crystals, which were so small that it was essentially a powder that could be filtered off and dried. It keeps well for several years. The CuAc2 at the time was used to produce lead acetate with Pb metal.
Anyway, I'd perhaps omit the boiling step, and work right away with highly concentrated solution. THat should allow you to filter off a significant amount of beautiful pure CuAc2.

DJF90 - 16-4-2008 at 17:37

Potassium triethanedioxatoferrate (III) crystals are bright green, and looked spectacular. I can remember making some at school when we were learning about transition metals, shame I didnt take any pictures :( Anyway heres the equation if anyone wants it:

FeCl3 + 3K2(C2O4) => K3[Fe(C2O4)3] + 3KCl

Basically we made weighed out stoichiometric amounts of the Iron (III) chloride and the Potassium oxalate. The FeCl3 was dissolved in half of the amount of water as the Potassium oxalate, and the two resulting solutions were mixed in a small beaker and covered. Unfortunately I have a feeling that the compound may be light sensitive, as the textbook has made the note "leave a sample exposed to sunlight or powerful light".

UnintentionalChaos - 16-4-2008 at 21:25

The above compound would be more easily understandable if named as potassium trisoxalatoferrate (III). Here's something that popped up on google about photosensetivity...

DJF90 - 16-4-2008 at 23:21

Sorry theres a typo... It's potassium triethanedioatoferrate (III), not triethanedioXatoferrate (III). It is equally understandable, its just that instead of naming it using the traditional name (oxalate), its named using the IUPAC accepted name (ethanedioate). Sorry for any confusion caused by my typo.

Magpie - 17-4-2008 at 09:52

re: Cu(OAc)2 from vinegar, Ca(OH)2, and CuSO4*5H2O

I filtered off the second crop of CaSO4 then placed the filtrate in 2 shallow dishes appropriated from the kitchen, w/permission. This morning there were hundreds of very small dark crystals forming evenly all over the bottom of the dishes.

This procedure does have its drawbacks in dealing with the CaSO4 ppt. The best removal of this most likely would be done when the suspension is near boiling due to CaSO4*2H2O retro solubility with temperature.

[Edited on 17-4-2008 by Magpie]

YT2095 - 18-4-2008 at 01:10

Originally posted by Magpie

Now my question for YT2095: How please did you make your nice dark green crystals? :o

I made a vinegar soln with GAA and tap water (roughly a 10% soln).
I then simply dissolved copper carbonate into it until all the Fizing stopped and some carbonate was left unreacted.
this was then filtered into a beaker and left to evaporate on a warm power transformer.
it took about a week to be be completely crystalised in the way you see in the pictures I posted.

Magpie - 18-4-2008 at 10:29

Thanks YT2095 for the method on your large crystals.

Mine have been growing for about 2 days now. I have two shallow dishes sitting in a window (eastern exposure) to warm in the morning sun as shown.

cupric acetate.jpg - 63kB

Magpie - 19-4-2008 at 21:15

My cupric acetate is nearly finshed crystalizing. Upon examination I find quite a bit of contaminating crystals that formed right at the end. They are clear needles and I assume that they are calcium acetate. There is also a gummy material mixed in with the crystals. I suppose this is the sugars/misc organics that come in with the vinegar as mentioned in another thread. So I can't really recommend this method. Next time I will use the method recommended by garage chemist, especially with regard to using GAA instead of vinegar.

16MillionEyes - 20-4-2008 at 21:05

I tried making Cu(AcO)2 the stupid way ( NaAcO + CuSO*5H2O) and although I did get very few dark colored crystals they seem to be more a matter of odd luck than an actual process. What I do get in relatively copious amount though, is some light turquoise solid that is just slightly less soluble than the CuSO4 or the NaSO4 so that it forms a thin layer on the bottom of the beaker. I don't know what it is although I suspected it to be Cu(AcO)2 before seeing actual pictures (some sites described it as what I have so I felt confident). Hopefully someone can tell me.

[Edited on 21-4-2008 by __________]

12AX7 - 21-4-2008 at 00:46

Could it be a I,II compound salt perhaps?

Crystallizing ternary mixtures like that can be a bitch. Instead of fractional crystallization, you're probably better off precipitating the important stuff (e.g., NaOH giving Cu(OH)2 and NaOAc and Na2SO4 in solution) and starting over. Outside chance you could seperate one or two phases from the dried, ground product with another solvent.


16MillionEyes - 21-4-2008 at 05:59

I took a picture of it, for a while I did consider it being a Cu(I) salt but I have no way of confirming it. One thing I did notice though, the solution smells strongly of acetic acid and I can't see why it should.

Any ideas?

YT2095 - 21-4-2008 at 08:13

that Almost looks like the copper carbonate I start with :P

woelen - 21-4-2008 at 08:33

This green stuff is a basic acetate, or a mix of basic acetate and basic sulfate.

NaOAc partly hydrolyses, because HOAc is a weak acid:

Dissolving: NaOAc --> Na(+) + OAc(-)
Hydrolysis: OAc(-) + H2O <---> HOAc + OH(-)

The hydroxide ions, formed in this hydrolysis reaction, precipitate with the copper(II) ions. No true Cu(OH)2 is formed, but a mixed Cu(OH)(OAc) salt, or a mix with sulfate ions as well. The remaining solution most likely is quite acidic and smells of vinegar.

16MillionEyes - 22-4-2008 at 06:23

I see, thanks. I did imagine the acetate was deprotonating the water and thus forming the hydroxide, the problem was I couldn't picture where the hydroxide would go so I didn't know exactly how to explain the vinegar smell. Now that you mention the possibility of a basic acetate it makes sense. :D
Anyhow, is this stuff good for anything useful/interesting?

chemoleo - 11-5-2008 at 08:11

For the record, here's a picture of triethylamine hydrochloride...not a good target for growing nice crystals :(

[Edited on 13-5-2008 by chemoleo]

triethylamine-HCl.jpg - 72kB

12AX7 - 11-5-2008 at 09:31

Nice picture of what looks like awful crystals! Pointy and thin, like urea. Man, I'm recrystallizing urea, my fingers keep getting poked when I stir around in the solution!


The_Davster - 11-5-2008 at 10:42

Also has remarkable resemblance to the crystals of phenol which grow under the cap by sublimation.

12AX7 - 11-5-2008 at 19:23

Ah, indeed! Only, those are fucking impossible to scrape off the sides! ARGH! :P


Magpie - 3-6-2008 at 10:46

I have been seeing what copper(II) compounds I can make with root killer CuSO4*5H2O. I have made Cu(OH)2, CuO, Cu(OH)2*CuCO3, and Cu(OAc)2*H2O.

The Cu(OAc)2*H2O was made from my homemade cupric hydroxide using 10% acetic acid made up from GAA. Below is a picture of a few crystals, which have a very dark color and smooth faces. They are prismatic and 3-4 mm wide. The end of the pestle shows the color of the crystals when ground. In the bottle is the basic cupric carbonate.

What has got me puzzled is the blue color of the carbonate and the acetate. I was expecting green for both. Brauer calls the carbonate "green copper carbonate", or "malachite." YT2095's acetate crystals were dark green in accordance with my CRC handbook.

(However, I have an abstract of a 1940's Russian journal article that says the acetate crystals will be dark blue.)

So, does anyone have an explanation for these apparent color discrepancies? What have been your experiences?

[Edited on 3-6-2008 by Magpie]

cupric acetate monohydrate.jpg - 50kB

woelen - 3-6-2008 at 11:25

This is exactly what I would expect for cupric acetate. I made cupric acetate as well and what I made is a very dark green/blue crystal mass, which on grinding becomes exactly as what you show.

This is a very common effect. When dark material is ground, then its appearance becomes lighter. A similar thing I noticed with anhydrous CuCl2. This is dark chocolate brown when in the form of somewhat larger crystals, but when it is finely powdered, it becomes more like mustard/yellow.

12AX7 - 3-6-2008 at 11:25

Hmm, azurite is blue carbonate. Maybe it wasn't hot enough? I recall azurite decomposes to malachite over time (which is why some blue colors look green on old murals, frescoes, etc.). Heat, I should think, should produce the thermodynamically favored product.


Magpie - 3-6-2008 at 12:34

Woelen says:

I made cupric acetate as well and what I made is a very dark green/blue crystal mass, which on grinding becomes exactly as what you show.

Well, thank you, this makes me feel better. I would like to hear from YT2095 to see what color his ground acetate crystals are.

Actually I made an error in the post above. I grew my crystals from homemade Cu(OH)2 instead of the basic carbonate.

I also have a batch growing using the basic carbonate and 10% acetic acid as per YT2095. I will have to wait to see what crystals I get.

I am also now firing some basic carbonate at 650C in my muffle furnace to get some pure CuO. Then I will try to grow acetate crystals from that, also using 10% acetic acid.

12AX7, I also thought I had made azurite but I don't think this will happen unless you use CO2 at a few atmospheres (per Brauer). If you add too much Na2CO3 I think it just washes out during the filtration/washing step for making the malachite.

I even tried to way undershoot the carbonate to make sure I had malachite. But in this case I think you just wash out the excess CuSO4 during the filtration/washing step. So, either way you get Cu(OH)2*CuCO3. As I suspected the product in the undershoot experiment was the same robin-egg blue.

I fired some of my basic carbonate at 650C and then weighed it. Comparing it to its original weight I calculated a carbonate/hydroxide ratio of 1.08.

[Edited on 3-6-2008 by Magpie]

YT2095 - 4-6-2008 at 01:48

certainly, here you go:

the far left is the crystaline copper acetate, in the middle is the same but ground up, and the far right is my copper carbonate as Azurite.
with the carbonate, if I`m going to have the lid off for any length of time, I fill the jar with CO2 when I`m finished and put it back on the shelf, it keeps nicely that way.

Magpie - 4-6-2008 at 08:08

Yes! Thank you very much YT2095! Although it seems your crystals distinctly have a green tint, when ground the light blue color is the same as mine and Woelen's.

Did you buy or make your azurite? If you bought it was it called "azurite" by the seller?

YT2095 - 5-6-2008 at 00:34

I made it myself from scrap copper that I save.
when I get enough I dissolve the lot in nitric acid, filter, and then react with K2CO3 soln to make the carbonate.
it`s worth pointing out that you must keep this mixture stirring all the time you add the K2CO3 soln, eventualy you reach a point where the color of the ppt will change you can end up with either the Azurite blue or the malachite green depending how much you add.
I stopped at the Blue.

Magpie - 5-6-2008 at 13:13

That's very interesting YT2095. I made my basic cupric carbonate per Brauer using root killer CuSO4*5H2O and washing soda Na2CO3. I haven't tried making any copper nitrate or using it as a precursor. Now I'm tempted to do that.

I have had some unexpected things happen while working from the CuSO4*5H2O. Several procedures I have seen specify heating cupric hydroxide to 60C or even 70C. I have found that if I get anywhere near 60C any cupric hydroxide I have will turn to the black CuO. So I stay away from any heating.

Another thing I have learned is that (for me at least) it is not all that easy to make cupric acetate in nice large crystals. So far the only success I have had is with Cu(OH)2 as precursor (in turn made from CuSO4*5H2O). With the other tries I just get the hundreds of tiny blue dots like I showed earlier in this thread.

My original goal was to find the most efficient way to make nice big crystals of cupric acetate monohydrate using root killer CuSO4*5H2O as the precursor. I selected this precursor as it is reasonably cheap and I just happened to have about 1kg on hand.

YT2095 - 6-6-2008 at 00:09

copper sulphate and washing soda will work just as well as my method, the only reason I do it the way I do is because nitric will dissolve copper metal in minutes without any fuss (and I have plenty of it), and I use K2CO2 because if I used the carbonate in any pyro mixture I wouldn`t want Any sodium ions to contaminate the color.
you still have to wash it very well after making it though.

as for the acetate you`l probably have to make a larger and more concentrated amount, and rather than crystalise this in a shallow dish try something a little taller and evaporate more slowly, it should give you larger crystals.

here`s another nice copper salt, perfectly clear blue, but lighter than copper sulphate.

it`s Copper Malate, simply made buy adding copper carbonate to malic acid soln and crystalising, it`s a little more difficult than some salts as it tends to get very viscous as it evaporates and can form a skin on the top, a bit like making sugar crystals.
the color is quite nice though.

Magpie - 6-6-2008 at 12:00


as for the acetate you`l probably have to make a larger and more concentrated amount, and rather than crystalise this in a shallow dish try something a little taller and evaporate more slowly, it should give you larger crystals.

Yes, I have been using evaporating dishes lately instead of the kitchenware shown in my first post. As you say this gives a slower evaporation rate. It seems patience (several days) is a virtue needed for growing copper acetate.

My attempt at growing the acetate crystals from copper carbonate was a failure. But my attempt using fired CuO seems to be progressing well. I placed a crystal from earlier growing in the dish as a seed crystal. It is growing! When it has finished I'll post a picture.

Magpie - 8-6-2008 at 16:01

Here's a picture of the big crystal of cupric acetate monohydrate grown from a seed crystal. Next to it are the normal sized crystals that started on their own.

These were grown from unfired CuO rather than fired CuO as I reported earlier. I couldn't get the fired CuO to dissolve.

Also shown is the blue homemade basic cupric carbonate compared to the green pottery grade of basic cupric carbonate. This color difference really puzzles me.

big crystal.jpg - 52kB

bereal511 - 8-6-2008 at 18:02

Just a conjecture, but perhaps your homemade basic cupric carbonate contains a larger portion of cupric carbonate than cupric hydroxide, rather than the 1:1 of your pottery grade (Is pottery grade malachite? I'm not sure). The powder has a more blue hue akin to YT2095's azurite than the greener malachite. How did you make it?

[Edited on 8-6-2008 by bereal511]

chemoleo - 8-6-2008 at 18:15

I'm impressed about the CuAc2 crystal. Can you manage to get a better shot, with better colour accuracy? Or is it really that dark?? Is it transparent to light at all?

UnintentionalChaos - 8-6-2008 at 18:30

Chemeleo- having grown CuOAc2 myself, I can tell you that it is intensely dark colored. A bright light behind it will illuminate the thinnest edges, while the rest remains dark. I have also tried to photograph them....they are black with a tinge of dark blue-green and shiny smooth crystal faces.

As for the discussion on malachite/azurite, I have left blue copper carbonate in a funnel over a flask that was slowly generating some CO2 and thought nothing of it, but the next morning, the blue copper carbonate (still wet) had turned green in the little round patch over the neck of the funnel. Maybe something like this can be useful in an intentional synthesis of malachite.

Magpie - 8-6-2008 at 19:59

from UnintentionalChaos:

Chemeleo- having grown CuOAc2 myself, I can tell you that it is intensely dark colored. A bright light behind it will illuminate the thinnest edges, while the rest remains dark. I have also tried to photograph them....they are black with a tinge of dark blue-green and shiny smooth crystal faces.

I couldn't say it better myself. When I look at my crystals in the picture above I can almost say I see a very dark green hint. But when looking at a thin edge in good light I see a gleam of blue.

Bereal I also thought that the green material just had less CuCO3 vs the blue. This is the conclusion I got when comparing the procedures in Brauer.

But when I fired samples of the two grades, then reweighed, my results supported an opposite conclusion. The ratio of CuCO3/Cu(OH)2 in my blue product is 1.08, in the green pottery product it is 1.24!

The first method in Brauer, p. 1024, (Green Cupric Carbonate), in the forum library, is what I used to make my blue carbonate. Starting material was CuSO4*5H2O.

Now the experience of UnintentionalChaos with CO2 applied to wet blue carbonate also supports the conclusion that the more carbonate the more green. Again, this is opposite to Brauer.

When you see the green patina of copper exposed to the elements as in a copper roof or work of art it is usually green. This would also indicate an exposure to CO2. An example can be seen in the picture below which is of a piece of copper sheet metal on a very old wind chime in my backyard.

[Edited on 8-6-2008 by Magpie]

wind chime.jpg - 104kB

woelen - 9-6-2008 at 22:35

As a side-walk, I tried to make copper propionate from basic copper carbonate. I mixed 1 ml of propionic acid with 2 ml of water and added some basic copper carbonate. The problem I am running into is that the material hardly dissolves. It only produces CO2 very slowly, even when heated to near boiling. The solution, however, gets a beautiful deep green/blue color, even when only a small fraction of all basic copper carbonate dissolves. It is interesting to investigate the differences between acetate and propionate.

I'll leave the solution for a few days, maybe the basic copper carbonate does dissolve, but very slowly. I have the impression that the color of the propionate resembles that of the acetate, but more intense and somewhat more green. If I get any crystals of this compound, then I'll post pictures in this thread.

Magpie - 10-6-2008 at 07:47

That's an interesting project Woelen and I look forward to your picture. I wonder if it will form the same type of structure, which is quite remarkable, as you show on your website for the acetate.

When I was collecting procedures for cupric acetate I noticed that those that did specify an acid concentration specified 8-10%. Maybe that would help in your dissolution process. (Acetic acid being a weak organic acid has higher ionization in the lower concentrations - maybe this helps.)

woelen - 12-6-2008 at 12:10

The propionate now is drying, it looks quite a lot like the acetate.

I now prepared the following salts (fine crystal mass):

1) copper acetate
2) copper monochloroacetate
3) copper trichloroacetate
4) copper propionate

I did a nice observation. In solution, only copper acetate and copper propionate seem to be heavily coordinated. The solution is darker than e.g. a copper sulfate solution of similar copper concentration, and the color is more greenish.

Copper monochloroacetate is not greenish at all in solution, it is more like a concentrated solution of copper sulfate. The picture below shows a solution of copper acetate and copper monoacetate.

A solution of copper trichloroacetate looks the same as a solution of copper monochloroacetate, plain blue copper ions

When the solid is made, then, however, the monochloroacetate becomes a coordination complex, the solid looks more like plain copper acetate. The trichloroacetate, also in solid form is not like the plain acetate anymore. It is bright blue like copper sulfate or copper nitrate. The picture below shows from left to right the plain acetate, the monochloroacetate and the trichloroacetate.

So, it seems as if the chlorine on the acetate ion makes coordination with the copper ion weaker (more labile). The monochloroacetate still is coordinated in the solid, but in solution the complex dissociates and a plain blue aqua complex is formed. The trichloroacetate is not coordinated at all, the solid also seems to contain a simple hydrated copper ion.

All three copper acetates are non-hygroscopic. They can easily be dried and form a nice dry non-sticky powder.

The solution of the propionate resembles a solution of a plain acetate.

When I have the dry solid copper propionate, then I'll make a nice write-up in a web page, but here you already have a few pics.

[Edited on 12-6-08 by woelen]

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[Edited on 7.1.14 by bfesser]

Magpie - 12-6-2008 at 13:04

Very interesting woelen. It seems that the Cl atom(s) are disrupting the resonance at the carbonyl end of the molecule. Or perhaps it could be a steric hindrance effect.

12AX7 - 12-6-2008 at 19:26

Should be the inductive effect at work. Roughly it should be as many times a weaker ligand as it is a stronger acid.


woelen - 17-6-2008 at 12:50

Here is the webpage about all the different compound I made. I also added lactate and formiae. The inductive effect, as described by 12AX7 indeed can explain all the observations.

Also have a look at the nice crystal I obtained with the formiate. There is a link inside the copper acetates page.

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: fixed external link(s)]

[Edited on 7.1.14 by bfesser]

indigofuzzy - 9-7-2008 at 17:48

Some patiently grown (took almost a month) Copper Acetate crystals:



The grid squares are 0.10 inches (2.54 mm)

Magpie - 9-7-2008 at 19:53

Vera nice. ;) What were your starting materials? What color are they? I.e., more blue than green, more green than blue, or blue-green, etc. (I'm thinking the camera may distort this color somewhat.)

YT2095 - 10-7-2008 at 00:43

wow, those are Beautiful specimens, Well Done! ;)

whilst on the subject of crystals, has anyone ever seen crystals growing on Top of the liquid layer?
I have some sodium oxalate that I`v made for use later, and am now letting it crystalise.
it has formed a "raft" like island on the top of the liquid layer and on this "Island" crystals are growing Upwards on it like little mountains.
I`v seen a skin form of certain solns before, but I`v never seen this happen.

[Edited on 10-7-2008 by YT2095]

chemoleo - 10-7-2008 at 03:42

That happens all the time in my long as you allow evaporation long enough (i.e. weeks)!
Usually the 'rafts' sink once they are to heavy, just make sure they don't fall onto your dangling seed crystals below otherwise you'll have the raft growing into the seed crystals!

I'm impressed about the CuAc2 crystals! How about you break of one crystal of the crystal mass, and grow that individually? Would love to see the 'space group' of it, and a bigger version!

[Edited on 10-7-2008 by chemoleo]

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