Sciencemadness Discussion Board

Uranium Trioxide

siegfried - 17-12-2012 at 15:04

Can UO3 be produced by reacting UO2(NO3)2 Uranyl Nitrate with NaOH?

Boffis - 17-12-2012 at 18:41

No, you get sodium uranate, usually as the dihydrate I seem to recall. If you just heat the uranyl nitrate it will decompose but its very difficult to get rid of the last little bit nitrogen oxides before the UO3 starts to decompose to dark U3O8 and eventually to UO2.

The best way to make UO3 is to add H2O2 to the uranyl nitrate solution to precipitate uranyl peroxide which is then filtered off dried and then gently heated in a shallow covered ceramic vessel. The oxygen rich atmosphere over the UO3 that is generated by the decomposition of the peroxide inhibits decomposition of the UO3. Uranyl peroxide can be very difficult to filter though but it decomposes at a low temperature (about 200 C I think). Other methods include heating ammonium uranate in an atmosphere of oxygen but I have never tried this.

Interestingly uranyl peroxide occurs naturally (studtite and metastudtite) and is as far as I am aware the only natural occurring, persistent, solid peroxide. At low temperatures it's both stable and highly insoluble, it is not soluble in dilute acid and so can be precipitated from an acid solution though it is soluble in excess sodium carbonate solution producing a deep orange colour which serves as a test for the mineral.

siegfried - 17-12-2012 at 18:57

I am trying to get a uranium compound that I can use to make uranium perchlorate. Seems like the UO3 route is problematic. Is there a way to use Uranyl Nitrate to make uranium perchlorate?

woelen - 17-12-2012 at 23:54

You want uranium perchlorate, or uranyl perchlorate? This is quite a difference. If you want the uranium salt then you need to reduce the hexavalent uranium in UO3 or the uranyl ion to a lower oxidation state, I think in water you only have the green uranium(IV) as a stable ion besides UO2(2+).

If you want uranyl perchlorate, then probably the route through the peroxide, decomposition of this and then dissolving in dilute perchloric acid is the most economic one. I'm not sure though how easily the perchlorate can be crystallized from water. I can imagine that this stuff is incredibly hygroscopic.

Boffis - 18-12-2012 at 09:33

An alternative route might be to precipitate the uranium as the potassium uranate using KOH and then dissolve this in dilute perchloric acid and let the insoluble K perchlorate settle out and filter. I agree with Woelen that the resulting solution may be difficult to crystallise. Have you checked the two inorganic chemistry text on uranium on the forum library (Mellors and the Textbook of inorganic chemistry)?

Why do you want uranyl perchlorate anyway if you don't mind me asking?

ScienceSquirrel - 18-12-2012 at 10:18

A nice reference on uranyl nitrate to perchlorate. It melts at 90C by the way!

http://actachemscand.org/pdf/acta_vol_27_p2146-2160.pdf

woelen - 18-12-2012 at 12:36

Interesting read. Also nice to see the difficulties in making pure U(4+) solutions and to see how sensitive these are to oxidation. Making uranyl perchlorate seems to be achievable even in a home lab setting, provided one has access to uranium-compounds. Unfortunately, obtaining uranium compounds in more than microquantities is nearly impossible these days.

blogfast25 - 18-12-2012 at 13:39

Quote: Originally posted by woelen  
Unfortunately, obtaining uranium compounds in more than microquantities is nearly impossible these days.


I passed on an eBay offer for 10 g of Uraninite a couple of years ago. A bit sorry now I didn't go for it back then...

IrC - 18-12-2012 at 19:06

Quote: Originally posted by woelen  
Interesting read. Also nice to see the difficulties in making pure U(4+) solutions and to see how sensitive these are to oxidation. Making uranyl perchlorate seems to be achievable even in a home lab setting, provided one has access to uranium-compounds. Unfortunately, obtaining uranium compounds in more than microquantities is nearly impossible these days.


Wish it would not ring alarm bells to mail you some from the states I love reading your experiments. A - you really know what you are doing, and B - me not so much (I can however build a mean Farnsworth Fusor). I love to learn from your write-ups.

neptunium - 18-12-2012 at 19:42

uranium ore can be obtain in pound (or kilogram) quantity rather easily and relatively cheap..
the american south west and other regions in the world are mining it and some areas are not off limit to the public
if you know what to look for you could literaly pick it off the ground!

about those depleted uranium bullets ...i dont know

siegfried - 19-12-2012 at 09:42

Thanks for all the suggestions. I was following the instructions for Uranyl Perchlorate on Megalomania's Method of Making Perchlorates. I' can get a pound of Uranyl Nitrate off Ebay ($725) or 4 oz for $250

ScienceSquirrel - 19-12-2012 at 19:43

Quote: Originally posted by siegfried  
Thanks for all the suggestions. I was following the instructions for Uranyl Perchlorate on Megalomania's Method of Making Perchlorates. I' can get a pound of Uranyl Nitrate off Ebay ($725) or 4 oz for $250


I have had a look round a few chemical suppliers and that is a reasonable price
Sadly it is also out of the range of the pockets of most home experimenters in those quantities.
4oz = 125 grams = $2 a gram.
10 grams would be enough for a lot of of home chemists and if it cost $30 it would be justifiable in terms of hobby expenditure.

[Edited on 20-12-2012 by ScienceSquirrel]

chornedsnorkack - 22-12-2012 at 05:07

Quote: Originally posted by Boffis  
No, you get sodium uranate, usually as the dihydrate I seem to recall.


Yes, with excess base.

Uranium VI being amphoteric, how easy is it to get clean uranyl hydroxide (pure of unwanted anions and cations)? Can you just apply proper stoichiometric amount of alkali, or perhaps a weaker base like ammonia, and then wash the uranyl hydroxide precipitate with distilled water? Or do uranyl hydroxide precipitates also incorporate large amounts of anions in form of insoluble basic uranyl salts?

woelen - 22-12-2012 at 05:27

In this thread this topic already was covered before. With alkali hydroxides you get insoluble alkali uranates. The sodium salt for instance is Na2U2O7. With ammonia you get (NH4)2U2O7. Obtaining pure UO3 cannot be done by precipitating with alkali hydroxides or ammonia. You need to add H2O2, which precipitates UO4.2H2O and then heat tthis peroxo-species.

urenthesage - 9-10-2016 at 11:46

I made UO3 by cooking uranium nitrate in air over 200oC. just make uranium nitrate with concentrated nitric acid and heat it strongly to dry and transform it.