Report on making metal sorbates

60g potassium sorbate was dissolved in 120g water. The salt dissolved quite easy once stirred, heating was on but it gave a clear solution long before it was hot. The purpose of this solution (total weight now 180g) was to use 30g portions, each containing 10g potassium sorbate, and perform double displacement reactions with metal salts and see what happens.

Copper:
- 8.3g CuSO4.5H2O was dissolved in 30g hot water.
- Add 30g of the potassium sorbate solution while stirring.
- A thick blue emulation formed that would not stir. 150ml water was added and the solution then stirred for 5 minutes. This was the result.


- Gravity filter. The filtration went quite fast, which was good. The filtrate was clear and there was a blue remainder.


- The remainder was washed in the funnel and then left out on the bench overnight to see how it dried. But the next morning the weight was almost the same.
- It was then dried on a steam bath. Some 5 hours drying was needed before the weight loss reduced to near zero. The result was this light blue powder; there was almost no colour change between the wet and dry product.


- 9.5g of product was recovered. It seems very light, as it filled up my little vial completely: this is unusual for something with a weight of under 10g.


Afterwards I poured concentrated HCl into the evaporation dish that still contained a bit of product expecting to get a green copper chloride solution. But after an hour it seemed that very little of the copper sorbate reacted with the acid; the crystals did turn a bit green in colour but not the acid.

Cobalt will probably be next.

Cobalt:
- 9.4g cobalt sulphate CoSO4.7H2O was dissolved in 30ml water giving a dark red solution
- Add 30g solution containing 10g potassium sorbate
- A light purple suspension formed.


- Gravity filter and rinse with water in funnel. The filtrate and wash water run through was red meaning either the cobalt sulphate was in excess or the product is soluble.


- The remainder looked more purple once it dried in the evaporating dish overnight.


- During drying on the steam bath a darker crust formed on top with more or less the same lighter purple underneath.
- Only 3.5g was recovered while much closer to 10g was expected (like the copper). Thus, I am not sure what actually formed.


Similarly to the copper salt described above, this cobalt salt is also not reactive with concentrated HCl. HCl was poured into the evaporating dish once the product was scraped out, but the remaining smears of product did not seem to have dissolved in the acid, not even 24 hours later.

Chromium:
- 8.7g chromium nitrate Cr(NO3)3.9H2O was dissolved in 30g water giving a black solution.
- 30g of the potassium sorbate solution, thus 10g of potassium sorbate, was added and stirred
- The solution immediately turned grey but with a hint of green or even blue depending on the light and who was looking!


- The solution was gravity filtered. Like the previous 2, filtering these compounds is easy thus quick. The filtrate was still a bit grey, and it was observed that this product is so fine some goes through the filter paper.
- The product was washed in the funnel with water, scraped into an evaporating dish and this is what is looked like after standing on the bench 48 hours.


- It was then placed on the steam bath. It takes more than 2 hours for the beaker I boil the water in to run out so I usually set an alarm for 2 hours and then go back to the shed. But when I walked past the shed an hour later I smelled a sweet smell, saw smoke, and on closer inspection observed that the product was decomposing with pops and small flames around the edge of the evaporating dish (where the temp must have been higher than the centre). I switched off the hot plate and squired in water.


This is the aftermath.


So was it purely the product that formed that had a low decomposition temperature of was there some nitrate present from the reaction that then reacted with the product due to the steam bath heat? I suppose one way to find out is to repeat the experiment but start with chromium sulphate instead of chromium nitrate.

Quote: Originally posted by Lion850

60g potassium sorbate was dissolved in 120g water. The salt dissolved quite easy once stirred, heating was on but it gave a clear solution long before it was hot. The purpose of this solution (total weight now 180g) was to use 30g portions, each containing 10g potassium sorbate, and perform double displacement reactions with metal salts and see what happens. Copper: - 8.3g CuSO4.5H2O was dissolved in 30g hot water. - Add 30g of the potassium sorbate solution while stirring. - A thick blue emulation formed that would not stir. 150ml water was added and the solution then stirred for 5 minutes. This was the result. - Gravity filter. The filtration went quite fast, which was good. The filtrate was clear and there was a blue remainder. - The remainder was washed in the funnel and then left out on the bench overnight to see how it dried. But the next morning the weight was almost the same. - It was then dried on a steam bath. Some 5 hours drying was needed before the weight loss reduced to near zero. The result was this light blue powder; there was almost no colour change between the wet and dry product. - 9.5g of product was recovered. It seems very light, as it filled up my little vial completely: this is unusual for something with a weight of under 10g. Afterwards I poured concentrated HCl into the evaporation dish that still contained a bit of product expecting to get a green copper chloride solution. But after an hour it seemed that very little of the copper sorbate reacted with the acid; the crystals did turn a bit green in colour but not the acid. Cobalt will probably be next.

I had some potassium sorbate on hand so I decided to try this. The manganese salt came out a butter yellow, not what I was expecting at all!



the potassium sorbate was in the form of small beads or prills; when they were poured into water to dissolve, they zipped around the beaker almost like tadpoles. It was very odd to see, and I'm having trouble imagining a mechanism

[Edited on 16-5-2021 by mayko]

Quote: Originally posted by mayko

I had some potassium sorbate on hand so I decided to try this. The manganese salt came out a butter yellow, not what I was expecting at all! the potassium sorbate was in the form of small beads or prills; when they were poured into water to dissolve, they zipped around the beaker almost like tadpoles. It was very odd to see, and I'm having trouble imagining a mechanism [Edited on 16-5-2021 by mayko]

I made manganese sorbate but it turned out a cream color - with a very slight hint of yellow to the eye but this is not picked up on photos.

- 5.8g MnSO4.H2O was dissolved in 50ml water. This gave a very pale pink solution.
- Add a solution containing 10g potassium sorbate under stirring, all reagents at room temp thus around 25C.
- A creamy suspension immediately formed.


- Stir for another 10 minutes.
- Gravity filter. Wash in funnel. The filtrate was clean and the remainder as shown here:


- Leave on bench for 24 hours, but the weight loss was minimal. Dry on steam bath until weight loss rate was near zero.
- Final product was 8.7g of light, fluffy soft powder. Drying did not change the color, still like cream with a very slight tinge of yellow, and just a hint of pink at some angles.


Mayko I don't know why the color of the products we got are so different. Which manganese compound did you use and what was the weights of the manganese compound and the potassium sorbate?

I could not find a description of manganese sorbate online.

Iron sorbate:

Iron (ii) sulphate monohydrate was dissolved in water. It dissolved with difficulty at room temperature but much easier when the water is near boiling. However by the time it was all dissolved the solution was not green-ish but as shown below; maybe I ended up with iron (iii) after the boiling and stirring?


A solution of potassium sorbate was added to the still very hot iron sulphate solution. A honey coloured suspension formed over a few minutes:


The solution was filtered. The filtrate was still coloured; maybe the iron sulphate was in excess. The remainder was rinsed in the funnel a few times and then dried on a steam bath. This was the appearance half way through the drying:


And the final bottled product.


An interesting side observation was that the stir bar was coated with a layer of similar colour. It would not rub off. I then stirred it in some concentrated room temp HCl, but the layer removed. I then heated the HCl while stirring, and once near boiling it dissolved the layer on the stir bar.

Nickel sorbate:

The only nickel salt I have lots off is nickel nitrate so that was my nickel source. Below shows the solution of nickel nitrate and potassium sorbate prior to mixing.


Once mixed, a pale green suspension formed. After stirring a few minutes the solution was filtered; the remainder was still a bit green so the nickel nitrate was probably in slight excess.


In the photo below the evaporating dish with the green substance shows the wet nickel sorbate remainder.


After seeing the chromium sorbate decompose on the steam bath I tried to dry the nickel sorbate in the sun under a steel dish, as both chromium and nickel were derived from nitrates. But it did not want to dry in the sun so onto the steam bath it went.

After 2 runs on the steam bath I had a near dry pale green powder (sadly I did not take a photo). I started the 3rd run and when I came back an hour later it had decomposed!


After scratching out most of the remains into the disposal bin I poured concentrated HCl into the dish to see if it would remove the rest. I was a bit surprised to see some bubbling. There was no smell, but holding a lit match to the bubbles they burned with pops just like hydrogen does. I thought hydrogen with the HCl could only be explained if there was elemental nickel present in the remains, which I did not expect. Is elemental nickel one of the products when nickel sorbate decomposes?

Quote: Originally posted by woelen

It must almost certainly be nickel metal, or some weird low oxidation state compound, but I never heard of that. This is a most interesting observation and definitely needs more investigation! Some metal salts can decompose to the metal and other stuff (e.g. silver oxide, mercury iodide, even silver nitrate on stronger heating), but with nickel I would not expect that. Iron can decompose to very reactive iron(II) oxide, but for nickel I do not know any reactive nickel(II) species and nickel(I) species I do not expect from sorbate.

The manganese compound you got looks more like what I expected, not sure what's going on. My first batch was 4.49 g manganese sulfate (presumably monohydrate, 0.027mmol) and 3.45 potassium sorbate (0.023 mmol). I must have messed up my stoichiometry, so I went back and did a second batch: 1.70g manganese sulfate ( 0.010 mmol) and 3.4 g potassium sorbate (0.023 mmol). This came out slightly lighter, but still distinctly yellow. I also tried manganese chloride (tetrahydrate, 1.95 g, 0.010 mmol) and potassium sorbate (3.24g, 0.022 mmol), but this was basically the same color.



Top row, L-R: manganese sulfate with 1:1 proportions, manganese sulfate with 1:2 proportions, manganese chloride with 1:2 proportions,
Bottom row, L-R: sulfur, corn starch, manganese sulfate

My first thought was iron contamination, since the ferric salt is a bright, school bus yellow. But I think that can be ruled out because:
* Neither manganese salt nor the potassium sorbate tests positive by thiocyanate
* the manganese chloride was specifically purified of iron, and
* the ferric salt is actually soluble in alcohol, forming an intensely colored solution. steeping the yellow salt in alcohol neither discolors the liquid nor bleaches the solid

So, I'm not entirely sure what's going on. The only thing I can think is that it's not an intrinsic property of the substance but caused by different particle size distributions under different reaction conditions?

Like I mentioned, the ferric salt is very bright orange-yellow, and unexpectedly dissolves in alcohol. I discovered this when I tried to rinse the precipitate with some IPA after filtering I'm trying to coax a recrystallization out of it though

I don't think the ferrous salt is very air-stable at all. Even stoppered at room temperature, the murky grey-green mixture developed an orange crust at the liquid/air interface overnight.