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Author: Subject: Cu, Ni and Mn selenites + photo
vano.kavt
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[*] posted on 4-12-2020 at 03:05
Cu, Ni and Mn selenites + photo


I made some selenites. First one is copper selenite dihydrate CuSeO3·2H2O. It is very nice blue powder or crystal, but i never seen crystal. It's insoluble in water.

I made it from basic copper carbonate and selenous acid:

Cu2(OH)2 CO3 + 2H2SeO3 → 2CuSeO3 + ......

Second one is nickel selenite dihydrate and NiSeO3·2H2O. It's light green insoluble powder. But i think this selenite is much soluble than copper selenite, because when water added it becomes like a suspension, which is yellow liquid.

I used nickel chloride hexahydrate and sodium selenite:

NiCl2 + Na2SeO3 → NiSeO3 + 2NaCl

Third one is manganese selenite • ?H2O. Its brown insoluble solid. I do not have much information about it. It is a rather rare compound because I did not even know the color before I made it.

I used manganese carbonate and selenous acid:
MnCO3 + H2SeO3 →MnSeO3 + H2O + CO2


received_396742351443054.jpeg - 508kB

[Edited on 4-12-2020 by vano.kavt]
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Bedlasky
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[*] posted on 4-12-2020 at 04:58


Hi and welcome to SM :).

These selenites have beautiful colour, especially nickel selenite.

Colour of manganese selenite is weird for II oxidation state. It looks like some Mn(III) or Mn(IV) compound. How precipitate looked when it was freshly made? Was there red precipitate mixed with brown precipitate? Mn(II) compounds are mostly only weakly coloured. There are some exceptions like MnO or tetraamonium hexamolybdatomanganate(II), but brown colour in 99% have compounds of trivalent and tetravalent manganese.




If you are interested in aqueous inorganic chemistry look at https://colourchem.wordpress.com/main-page/

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vano.kavt
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[*] posted on 4-12-2020 at 05:23


Quote: Originally posted by Bedlasky  
Hi and welcome to SM :).

These selenites have beautiful colour, especially nickel selenite.

Colour of manganese selenite is weird for II oxidation state. It looks like some Mn(III) or Mn(IV) compound. How precipitate looked when it was freshly made? Was there red precipitate mixed with brown precipitate? Mn(II) compounds are mostly only weakly coloured. There are some exceptions like MnO or tetraamonium hexamolybdatomanganate(II), but brown colour in 99% have compounds of trivalent and tetravalent manganese.


Thank you. Yes i know its Strange. I use manganese carbonate, which i bought in my town and i'm 100% sure that it is Chemically pure compound. As for the selenic acid it is the same. I did all the compounds in one day. I have no information. I tried English, Georgian, Russian and other languages, but to no avail.

[Edited on 4-12-2020 by vano.kavt]
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[*] posted on 4-12-2020 at 06:18


Welcome to SM Vano! I have 2 language in common with you, except Georgian, but probably you don't know Ukrainian :)

Edit: sorry, I didn't realise you are talking about selenous acid not selenic acid. So, please ignore the rest of the message.

Selenic acid seems to be a more strong oxidiser than sulfuric acid, it oxidise HCl to Cl2. So, I would suppose it can oxidise Mn(II) and you get not the selenic acid salt of Mn(II) but selenous acid salt (what should be name for this?) of some higher valency of Mn. Also some irregularity in color of the Mn compounds could suggest that the oxidising is not finished completely.

[Edited on 4-12-2020 by teodor]
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vano.kavt
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[*] posted on 4-12-2020 at 06:42


Quote: Originally posted by teodor  
Welcome to SM Vano! I have 2 language in common with you, except Georgian, but probably you don't know Ukrainian :)

Edit: sorry, I didn't realise you are talking about selenous acid not selenic acid. So, please ignore the rest of the message.

Selenic acid seems to be a more strong oxidiser than sulfuric acid, it oxidise HCl to Cl2. So, I would suppose it can oxidise Mn(II) and you get not the selenic acid salt of Mn(II) but selenous acid salt (what should be name for this?) of some higher valency of Mn. Also some irregularity in color of the Mn compounds could suggest that the oxidising is not finished completely.

[Edited on 4-12-2020 by teodor]


Thank you so much teodor. Unfortunately I do not know Ukrainian, But I use Ukrainian sources quite often. Of course, reaction between Mn 2 compounds and selenic acid is very interesting. I have kilos of selenium and selenous acid, but no selenic acid. It would be interesting to heat the selenic acid hydrate with manganese salt without water.

This is only sourse which i found two years ago. I mean here are hydrates with melting points. I would use any of them in this reaction.
https://uk.wikipedia.org/wiki/%D0%A1%D0%B5%D0%BB%D0%B5%D0%BD...

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

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

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