Sciencemadness Discussion Board - Potassium triiodoplumbate - K[PbI3]

Potassium triiodoplumbate - K[PbI3]

vano - 4-12-2020 at 01:38

I'm new hear. Hi everyone. Today i made Potassium triiodoplumbate K [PbI3]. It is a light yellow crystals, soluble in water, forms a crystalline hydrate. I have dihydrate which begins to lose water at 30 ° C. There are some reactions:

I used lead acetate trihydrate.
1) Pb(CH3COO)2 + KI → PbI2 + CH3COOK
I dried it and mixed it with concentrate KI solution.

2)PbI2 + KI → K [PbI3]

[Edited on 4-12-2020 by vano.kavt]

[Edited on 4-12-2020 by vano.kavt]

[Edited on 4-12-2020 by vano.kavt]

[Edited on 4-12-2020 by vano.kavt]

Lion850 - 4-12-2020 at 01:53

Hi Vano very interesting, first time I hear about this compound.

woelen - 4-12-2020 at 02:07

Interesting, this one also is new to me. I know of the mercury variation: HgI2 + 2I(-) --> HgI4(2-), but did not know that PbI2 also has a iodo-complex. I have made the beautiful bright yellow precipitate of PbI2 many times, but never went so far that I added so much KI, that it redissolves again.

How do you know that there is not excess KI in your pale yellow compound? My experience with the mercury compound is, that adding a stoichiometric amount of KI to a suspension of HgI2 in water is not enough to get all of it dissolved easily. You need to add excess KI to get all of it dissolved. Simply evaporating the solution then is not enough to get pure K2HgI4, you get a mix of K2HgI4 and KI instead.

If you add some of the pale yellow solid to water, does all of it dissolve easily?

vano - 4-12-2020 at 02:14

Tetraiodomercurates are great compounds. But lead also can produce tetraiodosalts, for example:

K [PbI3] + KI ⇌ K2 [PbI4]

I have never seen it.

vano - 4-12-2020 at 02:19

Yes it is unstable in dilute solution. It produce lead iodide and potassium iodide.

vano - 4-12-2020 at 03:23

Quote: Originally posted by woelen

Interesting, this one also is new to me. I know of the mercury variation: HgI2 + 2I(-) --> HgI4(2-), but did not know that PbI2 also has a iodo-complex. I have made the beautiful bright yellow precipitate of PbI2 many times, but never went so far that I added so much KI, that it redissolves again.

How do you know that there is not excess KI in your pale yellow compound? My experience with the mercury compound is, that adding a stoichiometric amount of KI to a suspension of HgI2 in water is not enough to get all of it dissolved easily. You need to add excess KI to get all of it dissolved. Simply evaporating the solution then is not enough to get pure K2HgI4, you get a mix of K2HgI4 and KI instead.

If you add some of the pale yellow solid to water, does all of it dissolve easily?

I think it is not excess KI in my pale yellow compound. I read about that in encyclopedia.

woelen - 4-12-2020 at 03:58

Interesting experiment, which I will try myself. I have Pb(NO3)2 and KI, so should be easy for me to try.

vano - 4-12-2020 at 04:21

Quote: Originally posted by woelen

Interesting experiment, which I will try myself. I have Pb(NO3)2 and KI, so should be easy for me to try.

good luck