sodium diuranate

{{Short description|Mixed oxide of uranium and sodium}}

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| CASNo = 13721-34-1

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| Formula = Na2U2O7

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| Density = 6.44 g/cm3

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Sodium diuranate, also known as the yellow oxide of uranium, is an inorganic chemical compound with the chemical formula {{chem2|Na2U2O7}}. It is a sodium salt of a diuranate anion. It forms a hexahydrate {{chem2|Na2U2O7*6H2O}}. Sodium diuranate is commonly referred to by the initials SDU.Meredith, A. D. (2013). Modified Sodium Diuranate Process for the Recovery of Uranium from Uranium Hexafluoride Transport Cylinder Wash Solution. (Doctoral dissertation). Retrieved from http://scholarcommons.sc.edu/etd/2466 Along with ammonium diuranate it was a component in early yellowcakes.{{cite book|last1=Kent|first1=James A.|title=Kent and Riegel's Handbook of Industrial Chemistry and Biotechnology|url=https://books.google.com/books?id=AYjFoLCNHYUC&pg=PA962|date=27 May 2010|publisher=Springer Science & Business Media|isbn=978-0-387-27843-8|pages=962–}} The ratio of the two compounds is determined by process conditions; however, yellowcake is now largely a mix of uranium oxides.{{cite journal|last1=Hausen|first1=D. M.|title=Characterizing and classifying uranium yellow cakes: A background|journal=JOM|volume=50|issue=12|year=1998|pages=45–47|issn=1047-4838|doi=10.1007/s11837-998-0307-5|bibcode=1998JOM....50l..45H|s2cid=97023067}}

Preparation

In the classical procedure for extracting uranium, pitchblende is broken up and mixed with sulfuric and nitric acids.{{cite web |url=http://www.mqes-uranium.com/metallurgy.html |title=MQes Uranium Inc. |language=en |access-date=2016-06-01 }} The uranium dissolves to form uranyl sulfate and sodium carbonate is added to precipitate impurities. If the uranium in the ore is in the tetravalent oxidation state, an oxidiser is added to oxidise it to the hexavalent oxidation state, and sodium hydroxide is then added to make the uranium precipitate as sodium diuranate.[https://patents.google.com/patent/US3034856A/en Purification of sodium diuranate]. Retrieved 2020-04-30

The alkaline process of milling uranium ores involves precipitating sodium uranate from the pregnant leaching solution to produce the semi-refined product referred to as yellowcake.[https://patents.google.com/patent/US3097919A/en Method of precipitation of sodium diuranate]. Retrieved 2020-04-30

These older methods of extracting uranium from its uraninite ores has been replaced in current practice by such procedures as solvent extraction, ion exchange, and volatility methods.Gindler, J. E. (1962). [https://web.archive.org/web/20170827072749/http://www.radiochemistry.org/periodictable/pdf_books/pdf/rc000068.pdf The Radiochemistry of Uranium] p. 39–235

Sodium uranate may be obtained in the amorphous form by heating together urano-uranic oxide and sodium chlorate; or by heating sodium uranyl acetate or carbonate. The crystalline form is produced by adding the green oxide in small quantities to fused sodium chloride, or by dissolving the amorphous form in fused sodium chloride, and allowing crystallization to take place. It yields reddish-yellow to greenish-yellow prisms or leaflets.

Uses

File:AW U glass bowl on fiestaware plate.jpg bowl in the shape of a cat, on top of a fiestaware plate, both previous uses of sodium diuranate.]]

In the past it was widely used to produce uranium glass or vaseline glass,{{cite journal|url=https://pubs.rsna.org/doi/pdf/10.1148/radiographics.13.3.8316677|doi = 10.1148/radiographics.13.3.8316677|title = A brief history of radioactive glassware|year = 1993|last1 = Landa|first1 = E. R.|last2 = Disantis|first2 = D. J.|journal = Radiographics|volume = 13|issue = 3|pages = 697–699|pmid = 8316677}} the sodium salt dissolving easily into the silica matrix during the firing of the initial melt.

It was also used in porcelain dentures to give them a fluorescence similar to that of natural teeth and once used in pottery to produce ivory to yellow shades in glazes.{{cite web |url=https://www.orau.org/ptp/collection/consumer%20products/dentures.htm |title=Uranium Containing Dentures (ca. 1960s, 1970s) |language=en |access-date=2016-06-01 }} It was added to these products as a mix with cerium oxide.{{cite journal |last1=Shcherbakov |first1=Alexander B. |last2=Reukov |first2=Vladimir V. |last3=Yakimansky |first3=Alexander V. |last4=Krasnopeeva |first4=Elena L. |last5=Ivanova |first5=Olga S. |last6=Popov |first6=Anton L. |last7=Ivanov |first7=Vladimir K. |title=CeO2 Nanoparticle-Containing Polymers for Biomedical Applications: A Review |journal=Polymers |date=17 March 2021 |volume=13 |issue=6 |pages=924 |doi=10.3390/polym13060924 |pmid=33802821 |pmc=8002506 |issn=2073-4360|doi-access=free }} The final uranium composition was from 0.008 to 0.1% by weight uranium with an average of about 0.02%. The practice appears to have stopped in the late 1980s.

References

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