Cobalt compounds

Quote: Originally posted by DraconicAcid

I don't think cobalt forms an aspirinate, but you can make potassium tricarbonatocobaltate(III) which is cool.

I prefer to make things i can pronounce easily lol, dosnt exactly trip off the tongue does it!! Nasty colour for a colbalt salt!

Thx for the link VV.

Slowly getting my pointless but colorful compound collection done.
I got 100 nice tubes with screw lids from China last week, only to trip over the step carrying them to the lab .

Might just be me being tight, but those tubes are costing more by the day!

WOW i could spend a fortune on that site!! Colbalt has some amazing colours.

[Edited on 28-11-2017 by NEMO-Chemistry]

Quote: Originally posted by NEMO-Chemistry

Nasty colour for a colbalt salt! .... Colbalt has some amazing colours.

Quote: Originally posted by DraconicAcid

Quote: Originally posted by NEMO-Chemistry   Nasty colour for a colbalt salt! .... Colbalt has some amazing colours. COBALT only has one L. And it might not be a nice colour (I think it's a nice, very dark green), but it is a useful starting material for cobalt(III) complexes. [Edited on 28-11-2017 by DraconicAcid]

My spelling is getting worse!

The salt i looked up was yellow ish, a nasty yellow ish. I better check i was looking at the right one. My new glasses will be here Friday .

Its the Blue colours i am mainly after, then the purples and pinks. None of this will make ANY sense until i complete the collection, but there is a method behind this madness.

Quote: Originally posted by DraconicAcid

Blue- tetrachlorocobaltate(II) ion. You probably want a large cation, such as choline or tetraalkylammonium.

Thanks alot, that has saved me alot of hunting around!.

I havnt worked with any COBALT salts before. They are a bit exotic price wise for me .

Quote: Originally posted by NEMO-Chemistry

Quote: Originally posted by DraconicAcid   Blue- tetrachlorocobaltate(II) ion. You probably want a large cation, such as choline or tetraalkylammonium. Thanks alot, that has saved me alot of hunting around!. I havnt worked with any COBALT salts before. They are a bit exotic price wise for me .

One can get CoCO3 here by the pound for a fairly good price. I also suggest that you try making Co Oxalate. It's a similar procedure to Ni or Fe Oxalate, and produces a nice salmon precipitate which, when decomposed, acts like the Ni and Fe salts.

Another good experiment is making the hydrates of CoCl₂!
You start out by neutralizing as much HCl with CoCO3 as you can, until you end up with a saturated solution. Some CoCl₂ * 6H₂O may crystallize if the solution is cooled even a bit. CoCl₂ * 6H₂O is a deep burgundy crystalline solid, and rather deliquescent. Heat this to obtain the purple dihydrate, or you can go all the way to the anhydrous, which is a light blue color. I did all three, and have a nice little collection. I also have Co Sulfate & Hypophosphite, both of which are a beautiful cherry color. Cobalt Silicate is very nice too, making a rich purple precipitate when a soluble silicate is added to a Co salt solution. When dried, it lightens up a bit. You can also make α-Co(OH)₂, which is a nice, bluish turquoise color by addition of ammonia to a Co salt solution, followed quickly by dilution with water. You can then precipitate it and store it. Picture below of α-Co Hydroxide. vvv

Quote: Originally posted by Tetra

Quote: Originally posted by NEMO-Chemistry   Quote: Originally posted by DraconicAcid   Blue- tetrachlorocobaltate(II) ion. You probably want a large cation, such as choline or tetraalkylammonium. Thanks alot, that has saved me alot of hunting around!. I havnt worked with any COBALT salts before. They are a bit exotic price wise for me . One can get CoCO3 here by the pound for a fairly good price. I also suggest that you try making Co Oxalate. It's a similar procedure to Ni or Fe Oxalate, and produces a nice salmon precipitate which, when decomposed, acts like the Ni and Fe salts. Another good experiment is making the hydrates of CoCl2! You start out by neutralizing as much HCl with CoCO3 as you can, until you end up with a saturated solution. Some CoCl2 * 6H2O may crystallize if the solution is cooled even a bit. CoCl2 * 6H2O is a deep burgundy crystalline solid, and rather deliquescent. Heat this to obtain the purple dihydrate, or you can go all the way to the anhydrous, which is a light blue color. I did all three, and have a nice little collection. I also have Co Sulfate & Hypophosphite, both of which are a beautiful cherry color. Cobalt Silicate is very nice too, making a rich purple precipitate when a soluble silicate is added to a Co salt solution. When dried, it lightens up a bit. You can also make α-Co(OH)2, which is a nice, bluish turquoise color by addition of ammonia to a Co salt solution, followed quickly by dilution with water. You can then precipitate it and store it. Picture below of α-Co Hydroxide. vvv

I've messed about with a few cobalt compounds in the past. Here are a couple of pictures of cobalt complexes.



and of course then there is cobalt(III)en perchlorate (en=ethylene diamine).



Which goes -

Attachment: My Movie.mp4 (3.9MB)
This file has been downloaded 836 times

Speaking of nickle.. I cant find the post where someone mentioned a coin made from it. I think it was a polish coin but cant remember. Looking online nickel is really expensive. Actually most things have shot up in price!

Last year I got 25KG Potassium Chloride from a garden supplier. the cost was £29 delivered. I looked last night to get some more, same stuff from same place is now £62

I dont buy many in large amounts, but those that i so have really gone up in price, copper sulphate in 10kg size is pretty expensive... Anyway anyone know which coin was mainly nickel?

I am waiting for my cobalt to arrive, having overspent on equipment i need to try and save on chems

Quote: Originally posted by woelen

How did you make the green carbonato-complex? That definitely is something I would like to reproduce.

Quote: Originally posted by DraconicAcid

Quote: Originally posted by woelen   How did you make the green carbonato-complex? That definitely is something I would like to reproduce. DOI: 10.1021/ja01504a004 Cobalt chloride, sodium carbonate, and hydrogen peroxide.

Quote: Originally posted by Tetra

Quote: Originally posted by DraconicAcid   Quote: Originally posted by woelen   How did you make the green carbonato-complex? That definitely is something I would like to reproduce. DOI: 10.1021/ja01504a004 Cobalt chloride, sodium carbonate, and hydrogen peroxide. Amounts? Process? Order of addition?

I accidently seem to have made a cobalt compound that gives a lovely dark green solution with concentrated HCl - but what is it?

The idea was to see if cobalt iodate could be made by doing a double displacement reaction between solutions of sodium iodate and cobalt acetate. This failed as far as I can see but I ended up with something interesting: a light grey powder that gives a lovely green solution with concentrated hydrochloric acid. How this happened:
- 10g NaIO3 dissolved in 100ml hot water. This NaIO3 was some 9 months old (in a clear jar) and a slightly brown, so there was probably some free iodine. It dissolved quite easy and gave a very pale brown solution.
- 6.4g (CH3COO)2Co.4H2O was dissolved in 30ml water, giving a red solution
- The cobalt acetate was slowly poured into the sodium iodate while stirring
- A maroon-purple suspension formed.
- The solution was then brought to boil while stirring. The reason I did this was to try and get a anhydrous cobalt iodate to ppt out; it is said to have low solubility at 100C.
- Close to boiling the color became more brown and it started to offgas lots of I2! See photo below.


- I initially thought this may be free I2 from the NaIO3 and continued to keep it boiling. After some 10 minutes the color of the solution was a bit lighter brown but there was no sign of the I2 coming off reducing.
- There was visible suspension, so I switched off the heat and let the solution cool down slowly, and then stopped the stirring. This have a brown solution with a dark layer on top (looking like I2 in water) and a heavy grey-pale blue ppt - I say heavy because it settled out quickly.
- The supernatant solution was decanted, and the ppt washed with ethanol to dissolve remaining I2. It was then gravity filtered. In the filter, the remainder, a dark grey powder, was twice washed with acetone by which time the acetone ran through clear. See photo of the dark grey remainder below.


- The filter paper with the remainder was put aside to be dried in the sun the next day.

I started to clean up. The reaction beaker had a difficult to remove layer of the grey ppt on the bottom. I added a bit of concentrated HCl to see if that would dissolve it...expecting the usual blue solution of anhydrous CoCl2. The grey layer dissolved in an instant...but gave a lovely green solution! See photo.


I started to look online mainly on Atomistry and Wikipedia to try to understand how cobalt wth HCl can give a green solution. What I did learn was that Cobalt makes many complex oxides, and in some circumstances iodine play a part in this. The oxides / oxide hydrates can have many colors, including grey.

The next day the power had lightened in color and after trying for some hours in the sun under a steel dish it appeared bone dry and light grey with just a hint of blue to the naked eye. See photo. Recovery was 3.4g


I tested the dry light grey powder with concentrated HCl, and again got a deep green solution. This time I stoppered the test tube with the green solution and put it aside to see if it remains green over time.


What is the grey powder that gives a green solution with HCl, and what is the solution? Did I accidentally make a complex?

Quote: Originally posted by Bedlasky

Lion850: Blue Co solution in conc. HCl isn't anhydrous CoCl2 but [CoCl4]2-.

Second attempt at cobalt iodate:

I had another go at making cobalt iodate, basically trying the same double displacement reaction but at lower temperature. And I filtered the sodium iodate solution before using.
- 5g NaIO3 in 30ml water, slight heat until all dissolved into a slightly brown colored solution.
- Filter the solution which cleared it up. Some dark specs as remainder; I don't know what this contaminant is, it does not appear to be free iodine.
- Dissolve 2.2g cobalt acetate in 12ml water, giving a red solution.
- Mixed the solutions as approximately 40C while stirring. The solution went through color changes as it cooled to room temp, see photos below. No I2 gassing off this time which was good!




- Vacuum filter, wash once with cold water in funnel, and keep sucking air through to dry it more. Color of this still moist product as below; bit of a mix of colors.


- Leave out exposed to air in the shed to dry; after some 3 days (when I again remembered to look at it!) the color was as below, which to me is lavender.

2.5g dry product recovered. I did 2 tests on the product which I think confirms it to be cobalt iodate:
- At high heat (on the center of the hotplate so should be around 300C) it decomposes. I2 fumes are seen and a black looking residue remains, probably a cobalt oxide.
- It dissolves readily in concentrated hydrochloric acid, releasing bubbles that smells like Cl2 gas and forming a green solution.

Report on making cobalt chloride CoCl2 anhydrous. My cobalt source is cobalt acetate - only because I got a reasonable quantity cheap! Seems that one advantage of using cobalt acetate is that when acetic acid is a side product this is easy to boil out of solution. Cobalt chloride was made as follows:

(CH3COO)2Co.4H2O + 2HCl = CoCl2 + 2CH3COOH + 4H2O

- 31g concentrated HCl added to a small beaker
- Slowly add cobalt acetate with stirring until a total of 30g added. This should have placed the HCl is excess.
- Leave stirring for a few hours. Very dark blue solution. Stop for evening, cover beaker with watch glass.
* Next day *
- Transfer very dark blue crystals and supernatant liquid to crucible and onto sand bath. Vinegar smell.
- Heat up on sand bath. Start to boil for while, with very strong vinegar fumes...had to open another door to get more draft through the shed. Boiling at around 115C.
- Once getting near dry break up with nickel spatula while still being heated to prevent hard layers forming, easy to break up.
- Initially a dark blue mass. Now seems to be only steam coming off, vinegar smell much less.
- Color becoming lighter as it dries. See photo below showing the mix of some crystals still hydrated (the darker) and most already the final sky blue color.


- Keep drying, check weight occasionally. Once all sky blue and weight seems constant (and close to the expected) dry for another 30 minutes and stop.
- Break into pieces small enough to go into the bottle and bottle while still very hot - compliments to whoever made these bottles, it did not crack!
- Final recovery was 15g, just half a gram or so less than the theoretical.

The leftover smears in the crucible quickly turned pink-red as it cooled down and started absorbing water. In the near future I want to try and make the red hydrate.

Pictures of the hydrated salt below.

Quote: Originally posted by teodor

CoCl2, CoCl2 * 9 H2O which is violet with red tint

Cobalt tungstate report: This was done in 2 stages:
2NaOH + H2WO4 = Na2WO4 + 2H2O
Na2WO4 + (CH3COO)2Co.4H2O = CoWO4 + 2CH3COONa + 4H2O

- 3.1g NaOH dissolved in 10g water. Clear solution.
- 9.8g H2WO4 was added in small quantities, waiting between additions until the yellow powder dissolved into the clear solution.
- The last H2WO4 added took some time to disappear, and the final solution had a very pale yellow tinge. See photo below.


- 9.4g cobalt acetate dissolved in 30g water, very dark red solution. See photo below.


- Add the sodium tungstate solution slowly to the cobalt acetate solution while stirring. Light purple colored suspension formed, photo below. Stir for 10 minutes.


- Attempt to go a gravity filtration - very slow! Ran out of patience and transfer to vacuum filter.
- Purple remainder and light red filtrate, see photo below. Seems the cobalt acetate was in slight excess. Wash with water in filter twice, clear run-through.


- Dry on steam bath. As the product dried the color lightened a bit (more distinct to the naked eye than on the photos).
- 11.8g of light purple of presumably cobalt tungstate recovered. Photo of final product below.


I searched online for the color of cobalt tungstate and various colors are mentioned, like red. However there are some photos that shows a similar color to what I achieved, for example:
https://www.reddit.com/r/chemistry/comments/big18p/insoluble...

Report on making cobalt formate Co(HCO2)2

Cobalt formate was made by reacting formic acid (90% AR grade) with cobalt carbonate (from a ceramic supplier):

2CH2O2 + CoCO3 = Co(HCO2)2 + CO2 + H2O (although the final product was most likely the dihydrate).

- 9g of 90% formic acid in small beaker
- 10.7g of cobalt carbonate measured out, add 2 small portions.
- Not much of a reaction. Add 15ml water and gentle heat on hotplate.
- Reaction start when warm (beaker can still be held by fingers) with bubbling. As expected when reacting a carbonate and acid, but not as vigorous as the common strong acids.
- Add all remaining CoCO3, stir and gentle heat. Solution color slowly changes to red.
- After the reaction seemed to have stopped add another 2g formic acid to ensure acid in slight excess.
- Keep stirring another 30 minutes, no more bubbles.
- Seems still to be some unreacted purple powder - cobalt carbonate? Transfer to bigger beaker, in 250ml water, bring to boil. Nearly all solids dissolved into red solution.
- Gravity filter hot. Red filtrate, a very small amount of purple-ish remainder.
- Steam down solution slowly, crystals started to appear around 100ml point.
- Switch off hot plate and leave to cool down slowly overnight.
- Next day: lots of crystals in the cold solution (morning ambient in the shed around 18C). Decant the supernatant red liquid (this will be the second crop) and transfer the red/maroon crystals to some paper towel and then a watch glass to dry. Crystals looks like little plates.
- Seems completely dry after a few hours. Picture of the dry product below.


- 9g recovered, 2nd crop still to be added.


When steaming down the beaker with the second crop, I got tied up and when I went back it was completely dry and it was turning a more purple color. I did not know whether the purple was the anhydrous salt or whether it started to decompose; as the decomposition temp of cobalt formate is said to be around 140C. I added 50ml water to the purple/red mix and all dissolved back into a red solution again, so it would seem the purple is the color of the anhydrous salt or a lower hydrate.

So far this is the prettiest cobalt salt I have made.

[file]83372[/file]

Quote: Originally posted by Bedlasky

Quote: Originally posted by teodor   CoCl2, CoCl2 * 9 H2O which is violet with red tint Are you sure about that? I never heard about nonahydrate. Just about hexahydrate (red solid which crystallize out from CoCl2 solutions at room temperature), dihydrate (violet solid, observable intermmediate during dehydratation of hexahydrate) and anhydrous (blue solid). [Edited on 18-9-2020 by Bedlasky]

Probably you are right. So, I've made probably CoCl2 * 2H2O from CoCl2 * 6H2O by this method. I didn't check the water contents, it was just an experiment to check how the alcohol acts on the hexahydrate (in some old children book I have an experiment of destroying CoCl2 * 6H2O by acetone, so I just was experimenting with this approach). Here are the photos:







[Edited on 23-9-2020 by teodor]

Atomistry says “Cobalt iodide is most readily obtained in solution by warming the finely divided metal with water and iodine” and this was my preferred route….but I did not have cobalt powder. So I made cobalt powder by reducing cobalt sulphate with sodium borohydride:

CoSO4.7H2O + 2NaBH4 = Co + H2 + B2H6 + Na2SO4 + 7H2O

- 17.9g cobalt sulphate hydrate dissolved in 110g water
- 10g NaBH4 was added in VERY small portions, each time waiting for the fierce bubbling to die down before adding the next (mainly H2 coming off as far as I know; looks good then set alight in the beaker). This is more or less double the stoichiometric amount, as seems to be recommended when I was reading up on reducing metal compounds to the metal.
- The final solution was black and was vacuum filtered. The remainder was a dark grey / black powder which was rinsed in the funnel with lots of water.
- The still-wet remainder was tested with concentrated hydrochloric acid. It very quickly dissolved with some bubbling into a light blue solution, which turned maroon-ish when water was added. All the powder dissolved with nothing left over. So it seems it was mostly cobalt powder.
** I later saw that a very small amount of black ppt settled out of the filtrate once it cooled, and this black ppt did not seem to react with HCl. I don’t know if this was maybe a boron compound.
- My aim was to react 10g of iodine to form cobalt iodide. The reduction of the cobalt sulphate should have yielded 4g metallic cobalt, which was way in excess to react with 10g iodine.
- The rest of the wet powder was added to a beaker with 100g water, and 5 gram iodine crystals. After some time of stirring the iodine was gone and the solution a dark red. 5 more grams of iodine was then added, giving a total of 10g.
- The iodine again seemed to react in some 10 minutes but the stirring was continued for another 2 hours (I got called away). The solution was then gravity filtered to remove the excess cobalt.
- The filtrate was a red solution, see photo below.


- A few drops of this red solution was added to a lead nitrate solution, giving a bright yellow ppt of most likely lead iodide. See photo.


- The solution was boiled down. No I2 fumes were observed at boil which was seen to indicate there was not free iodine in the solution. Once the volume was less than 50ml it was transferred hot to the desiccator, the still warm solution boiled a bit more as vacuum was applied.
- After some 24 hours there was a dark red-ish mass in the desiccator. Photo below.


- But when I looked again a few hours later it turned black/very dark green! Photo below.


- After a further 48 hours (total 72) in the desiccator the contents appeared solid from the outside and it was taken out. But it was still wet under a crust, and once in air it started to fume gently and turned to green where it was thinly layered. Photo below, although it did not really capture the fuming.


Atomistry do mention a black form of CoI2 that slowly turns green on exposure to air but it does not mention any fuming in air. The fumes don’t ready have a smell, could be a hint of a smell similar to H2S.
- I then put it on a steam bath. It seemed to first melt to a black liquid and then form a crust on top which prevented further drying. Once this crust was broken it fumed again.
- I decided that it cannot be easily dried in air. Online reading said cobalt iodide was soluble in acetone. I added acetone and got a dark green solution.


- This solution was filtered, and there was no remainder. Dripping this solution into a lead nitrate solution again gave the bright yellow ppt of lead iodide. The dark green filtrate was bottled and labelled “cobalt iodide in acetone”. See photos below.


Getting solid CoI2 out of a water solution probably needs working in an inert atmosphere?

As a side note, the cobalt remainder that was left when the iodine solution was filtered off has been exposed to air for some days now and is turning olive green, see below. I don’t know which compound is forming?

Cobalt monosulphide CoS

A double displacement reaction was performed between sodium sulphide solution and cobalt sulphate solution. A black ppt was immediately obtained. After some 30 minutes of stirring the solution was vacuum filtered, and the remainder washed with water in the funnel. During all of this there was only the occasional hint of H2S smell. Photo of the wet remainder below.


The remainder was dried on a steam bath, the dry product is more brown. Photo below. There was no smell while it dried.


The product does not readily dissolved in hydrochloric acid, but it does dissolved in dilute nitric acid. However, there is hardly any bubbles when it dissolves in nitric acid and no smell of H2S.

Textbook of inorganic chemistry vol 9-1 says that CoS does not always react with HCl but does dissolves in HNO3; and colors can be black or brown. So I think there is a reasonable chance I ended up with CoS (or another sulphide) but I'm not 100% sure.

Cobalt sulphate & cobalt iso-butyrate

As a beginner in the cobalt chemistry I've made just some cobalt sulphate. I put a piece of cobalt metal in diluted H2SO4 and found this after 3 days.



I had attempt to crystallise cobalt iso-butyrate but it doesn't want to crystallise at all. But I must confess my starting compounds were not pure.

[Edited on 2-11-2020 by teodor]

Quote: Originally posted by teodor

As a beginner in the cobalt chemistry I've made just some cobalt sulphate. I put a piece of cobalt metal in diluted H2SO4 and found this after 3 days. I had attempt to crystallise cobalt iso-butyrate but it doesn't want to crystallise at all. But I must confess my starting compounds were not pure. [Edited on 2-11-2020 by teodor]

Quote: Originally posted by MidLifeChemist

Quote: Originally posted by teodor   As a beginner in the cobalt chemistry I've made just some cobalt sulphate. I put a piece of cobalt metal in diluted H2SO4 and found this after 3 days. [Edited on 2-11-2020 by teodor] Very nice, the Cobalt Sulfate looks beautiful. Simple experiments are sometimes the best.

Quote: Originally posted by Bedlasky

Just mix some ordinary cobalt salt (chloride, sulfate, nitrate) with ligand. Ligand exchange in cobalt complexes is usually quick (unlike trivalent chromium where ligand exchange is slow, this is reason why Cr(III) complexes are often make from Cr(II) or Cr(VI) compounds).

Quote: Originally posted by teodor

Edit: this relation is really strange for me, as for a beginner, because Co behaviour towards nitric acid is really unusual - HNO3 usually oxidises a metal to higher valency, but it seams there is no Co(NO3)3 exists (with H2O ligands) but [Co(NH3)6](NO3)3 does exist.

Quote: Originally posted by Bedlasky

These ligands like ammonia, edta, cyanide etc. stabilise Co(III) but I don't know why. Hexacyanocobaltate(II) is even oxidized by water to hexacyanocobaltate(III).

Quote: Originally posted by Lion850

** I later saw that a very small amount of black ppt settled out of the filtrate once it cooled, and this black ppt did not seem to react with HCl. I don’t know if this was maybe a boron compound.

Cobalt phosphate:

I first tried to dissolve cobalt carbonate in phosphoric acid (which worked so well with copper carbonate) but it became a sticky mess. I then tried a double displacement reaction. The only soluble phosphate salt I had was potassium dihydrogen phosphate, KH2PO4.

- 15.7g of KH2PO4 dissolved in 70ml water, with some heat and magnetic stirring soon gave a clear solution.
- 14g cobalt acetate Co(CH3COO)2.4H2O dissolved in 40ml water, all dissolved into a dark red-purple solution.
- Add the cobalt acetate solution slowly to the potassium dihydrogen phosphate while stirring. Immediately got a lavender solution. Continued to stir for 15 minutes. Photo below.


- Vacuum filter. Filtrate a very pale red. Rinse in funnel with 2 portions of water. Remainder a mix of lavender and darker purple, photo below.


- Leave on bench overnight. The next day the weight had reduced by 3g and the color was more uniform. Photo below.


- Dry on steam bath for many hours until weight stopped reducing: from 52g to final weight of 12.1g.
- Powdered in mortar, difficult as the product is quite hard.
- 11.8g dry lavender powder bottled.


Question: What is the correct equation for this reaction? Is it

2KH2PO4 + Co(CH3COO)2.4H2O = 2KCH3COO + Co(H2PO4)2 + 4H2O

but does Co(H2PO4)2 even exist?

Once other observation: cleaning the equipment afterwards showed the product dissolved easily in concentrated HCl giving a lovely blue solution, most probably CoCl2.



-

Cobalt gluconate.

- 10g calcium gluconate was dissolved in 100g water. Once near boiling the salt completely dissolved giving a clear solution.
- 6.6g cobalt sulphate heptahydrate was dissolved in 30g water, this gave a dark red solution.
- The hot cobalt sulphate solution was added to the hot calcium gluconate solution, and stirred for 40 minutes while keeping it very hot.
- Stirring was stopped and a heavy white ppt quickly settled, presumably calcium sulphate. The solution was then filtered and a wine-red remainder obtained.


- The beaker with the remainder was placed in a bigger beaker of boiling water. After some hours all that was left was a sticky maroon coloured layer.
** The last time I tried this experiment, a month or so ago, I obtained the same sticky stuff. I then put it on a sand bath at around 200C but it decomposed into a mess. So I know to try something different.
- Add 150ml methanol to the beaker and boil, topping up with methanol from time to time. This worked recently when I made copper gluconate, but it had little effect on the cobalt: it remained a sticky blob.
- I then added xylene to get a higher boiling temperature. After boiling for 30 minutes or so it became a swollen mass!. Photo below.


- This mass was no longer sticky. I broke it into smaller pieces so the stirring could work, and stirred it for another 10 minutes or so in near-boiling xylene. The result was a coarse powder.
- Most of the xylene was decanted off, and the rest filtered off. The remainder was a coarse powder, still wet with xylene as shown below.


- The product was then dried on a steam bath. The xylene evaporated quickly, after 1 hour the weight was steady.
- Final recovery was spot on 10g of a dry free-flowing powder. Colour is probably maroon, anyway a somewhere between red-pink and purple.


10g represents a yield percentage of 95 which is almost to good to be true. This powder is very fluffy; it occupies a larger volume when one considers the weight is only 10g.

Cleaning the beaker with concentrated HCl immediately have the lovely blue colour of cobalt chloride.

Anhydrous CoCl2

Today I prepared anhydrous CoCl2 by reaction of cobalt acetate 4 hydrate with acetyl chloride in benzene. The procedure is from Brauer, p. 1515.

Co(AcO)2 * 4H2O + 6 AcCl = CoCl2 + 2 Ac2O + 4AcOH + 4HCl

I didn't notice the evolution of HCl, probably it was fully absorbed by the liquid.
The colour change sequence during this reaction is very beautiful, unfortunately I've made a photo only of the start and finish state.



Some notes about preparation of the cobalt acetate 4 hydrate powder. I made it by a reaction of cobalt carbonate and acetic acid, but crystallisation without seed crystals is a challenge. I've got the seed crystals by evaporating water solution with acetic acid to the syrupy state and adding ethanol to this.
I did 2 washing of Co(AcO)2 * 4H2O - first with water, and after that the mass became very dense and second with ethanol which converts crystals to a very fine and diffuse uniform powder.



[Edited on 11-7-2021 by teodor]

Oh, sorry, I don't know why I read acetic anhydride instead of acetyl chloride .