Wikipedia:Requests for mediation/Depleted uranium and related articles/UO3 vapor

What is the importance of uranium trioxide vapor as a product of the combustion of uranium?

This is a pretty clear cut case, UO₃ gas does not exist in any natural condition on planet earth. The pressure required is so low that it can only be artificially induced. Ten Dead Chickens 05:27, 22 February 2006 (UTC)

The case is not clear cut, but substantial volumes of UO₃ gas, which quickly disperse and condense, are produced by uranium combustion in air. --James S. 03:00, 28 February 2006 (UTC)

As synthesis and original research are prohibited on wikipedia, any relevant discussion of this matter would have to come from a source that specifically addressed the impact of the vapor form of this usually solid substance on human health...all in the same article, and not cobbled together from multiple resources, as synthesis is prohibited. As I am unaware of any single resource detailing the impact of vaporous uranium trioxide on human health, it is difficult to participate in a relevant discussion on this matter. But if anyone can provide a single resource addressing this, please bring it to my attention. Dr U 05:58, 22 February 2006 (UTC)

Salbu, B.; Janssens, K.; Lind, O.C.; Proost, K.; Gijsels, L., Danesic, P.R. (2005) "Oxidation states of uranium in depleted uranium particles from Kuwait." Journal of Environmental Radioactivity, 78, 125–135: http://www.bovik.org/du/Salbu-uranyl-detected.pdf Abstract: "Environmental or health impact assessments for ... DU munitions should ... take into account the presence of respiratory UO₃...." The prohibition on original research only applies in article space, and even there you are allowed to use your brain. --James S. 00:18, 7 March 2006 (UTC)

As Dr U said. The leap between a mass spectrograph detection; the production of this species in volume by kinetic impact; it's subsequent absorption in human lungs; and the potential health impacts of such exposure, is a chain of synthesis and supposition that is not supported by the references given. --DV8 2XL 00:58, 23 February 2006 (UTC)

On the contrary, the references fully support my assertions. --James S. 03:00, 28 February 2006 (UTC)

Then it would be no problem for you to find a parade of experts that are willing to back you up and do so with their names public. --DV8 2XL 05:55, 28 February 2006 (UTC)

Here are more than a dozen, not that I agree with all fifteen of those viewpoints. --James S. 00:22, 7 March 2006 (UTC)

The Lone Star Iconoclast News, you have got to be kidding. --DV8 2XL 02:08, 7 March 2006 (UTC)

Volatility of UO₃

James has uploaded the Ackermann paper here (files a60-***.jpg). The quoted values for UO₃ gas are Δ_fH = −830.5 kJ/mol, Δ_fS = −79.5 JK⁻¹mol⁻¹: this gives Δ_vH = +393.3 kJ/mol, Δ_vS = +182.3 JK⁻¹mol⁻¹ (other thermodynamic data from NIST), a volatility which is slightly less than that of molybdenum trioxide. Physchim62 (talk) 02:40, 23 February 2006 (UTC)

I've only had time to skim them, but to me it is still a stretch to claim that UO₃ will form anything but trace amounts of gas at STP or that it would survive for any length of time, based on what is presented there. In fact given the complexity of the U-O system in general at high temperatures, I would suggest any statement about the compositions of uranium oxide vapors created under field conditions would be highly speculative at best. That uranium burns, that it forms fine combustion products when it does, and that it is unlikely that inhalation of these suspensions would prove beneficial to any living organism was never part of the debate. However at first glance, based on what I see in these papers Uranium trioxide#Gas as aerial uranium combustion product needs to be removed as a misinterpretation, if not worse. --DV8 2XL 03:31, 23 February 2006 (UTC)

That "small amount" can be quantified, either with the data I quoted above or, even better, directly from the experimental results quoted in the Ackermann (1960) paper: at 1000 K, the vapor pressure of uranium trioxide is 2.4×10⁻¹² atm, equivalent to 6.7 ng/m³ uranium. The experimental design used in that paper is based on the uranium oxide vapour condensing to a solid very rapidly, before it leaves the apparatus, so could not be used to support the idea of a long-lived gas dispersing in the atmosphere and entering the lungs as such. None of the other papers offers any greater insight into gaseous UO₃. Physchim62 (talk) 07:54, 23 February 2006 (UTC)

Please check your math. You may be quoting the minimum pressure at which the reaction occurs. Did you see the phase diagrams from the Gmelin Handbook? --James S. 11:19, 23 February 2006 (UTC)

At the end of the Ackermann paper (at the end) it is stated that the highest pressure at which they could show the existence of gaseous UO₃ was 10⁻⁷ atm. The phase diagrams in Gmelin are for the solid state. Physchim62 (talk) 21:37, 23 February 2006 (UTC)

You can check my maths yourself: it is equation (10), p354:

−R'TlogpUO₃(atm) = (84.9±0.5)10³ − (31.7±0.5)T cal/mol: R' = 4.576.

Physchim62 (talk) 22:05, 23 February 2006 (UTC)

I removed the section Uranium trioxide#Gas as aerial uranium combustion product as it seems clear from the above that UO₃(g) is irrelevant to the subject. James has reinserted it claiming that this discussion has justified its inclusion.

I am at a loss to see how we can make any progress here if this sort of obsteperous behavior continues. --DV8 2XL 19:27, 23 February 2006 (UTC)

1000 Kelvin is the bottom of the range at which Ackermann et al. describe the effect. --James S. 03:00, 28 February 2006 (UTC)

What temperature would you prefer that we discuss? There is an upper limit, as UO₃ (g) decomposes to UO₂ at high temperature (discussed briefly in the Ackermann paper). Physchim62 (talk) 06:13, 28 February 2006 (UTC)

1500K would be a good place to start, but based on the Mouradian and Baker temperature graphs, it could be 2000K or above; I think primarily lower oxidation states occur in those regions. Also I think we need to review the behavior of spalling in fire. The "Ignition of Uranium" article is adjacent to Baker's other article in the temperatue physics journal article. --James S. 19:51, 28 February 2006 (UTC)

Importance of vapor pressure

We have established that UO₃ is a bona fide combustion product of uranium, and so it is perfectly reasonable to mention that on Uranium trioxide. The issue is how much of it is produced when uranium burns in air. I am pretty sure that the the text of the scanned Gmelin pages indcates that the vapor pressure of sublimation is not the same as the combustion production. --James S. 20:50, 23 February 2006 (UTC)

Chemical research journals are full of papers reporting on the discovery of this or that ultra short-lived compound. While some of them may be important as reactive intermediates in complex multi-stage reactions, a great many of them are non-notable. Uranium trioxide gas - unless it can be shown by reference otherwise - is one of the latter. --DV8 2XL 21:06, 23 February 2006 (UTC)

The vapor pressure is important as it shows the maximum amount of a substance which can exist in the gas phase at a given temperature. If the quantity of a substance in the gas phase is greater than its vapor pressure, it will condense. Physchim62 (talk) 22:20, 23 February 2006 (UTC)

I agree: "UO₃(g) molecules will adhere to surfaces, precipitating out of air as nanometer-scale particles and film." DV8 recently removed that section and called me obstreperous when I put it back. I changed it to your terminology. --James S. 00:22, 24 February 2006 (UTC)

The vapor pressure of sublimation is not the same as combustion, where U₃O₈ can split into UO₃ + U₂O₅. Right now I'm thinking UO₃ could be anywhere from 0.12% to 55% of the combustion product, but I need to do this again on a spreadsheet or program. And probably scan the high-temperature 1961 article. Anything else I need? I have noticed no opposition to the fact that the inverse cube of diameter is proportional to surface area, or that increased partial pressure of O₂ (or O ions, in plasma) substantially increases the probability of formation of oxides, or my suspicion that the Ackermann's 1960 mass spectrograph wouldn't fluoresce at pressures too far from a vacuum. --James S. 05:19, 7 March 2006 (UTC)

So do you agree that UO₃ gas could not be inhaled, either by soldiers or by civilians? Physchim62 (talk) 04:59, 24 February 2006 (UTC)

No, it surely is. The only question is how much. --James S. 05:19, 7 March 2006 (UTC)

Salbu's identification of U(VI)

Salbu, et al., (2005) emperically identified uranyl ion by spectroscopy inside tanks and depots after uranium fires therein. Emperical evidence trumps theoretical speculation; thus it is in fact shown as requested. --James S. 21:24, 23 February 2006 (UTC)

And that proves the free existence of the gas in question in concentration how? --DV8 2XL 21:27, 23 February 2006 (UTC)

As Salbu themselves point out, this is not a proof for the existence of UO₃ (although neither does it allow people to rule it out completely); the best fit to the results (and the closer to described uranium chemistry) is U₃O₈. Please remember that one in three of the uranium ions in U₃O₈ is in the +6 oxidation state (uranyl). Physchim62 (talk) 21:37, 23 February 2006 (UTC)

And of course U₂O₅ is in easy equilibrium with U₃O₈ anywhere UO₃ dissolves, is it not? --James S. 03:00, 28 February 2006 (UTC)

Plasma hypothesis

One point that everyone has appearently missed so far is the issue of surface area, and its effect on production. I would point out that U₃O₈ surface area in a burning plasma is several orders of magnitude greater than that of its particulate form. --James S. 20:50, 23 February 2006 (UTC)

Everybody including your "verifiable peer-reviewed sources" as well I note. --DV8 2XL 21:06, 23 February 2006 (UTC)

A burning plasma producing low oxidation state combustion products.

A "burning plasma", almost by definition, has a low oxygen content, so would tend to produce UO₂ as the combustion product. This is consitent with Salbu's findings: the only instance where more oxidized forms of uranium were found was in particles from the Al Doha munitions dump fire (i.e. formed in circumstances where an adequate oxygen supply was available). The surface area of the U₃O₈ has no bearing on its thermodynamic behavior, merely on the kinetics of any reaction. Physchim62 (talk) 22:12, 23 February 2006 (UTC)

An analogy is the candle flame. As you are probably aware, a burning candle produces particulate amorphous carbon, commonly known as soot. In fact, the soot particles are responsable for the yellow color of the flame. The carbon is not completely oxidized to carbon dioxide because the flame contains insufficient oxygen. Physchim62 (talk) 22:26, 23 February 2006 (UTC)

As the surface area of U₃O₈ particles cooling from the plasma of a flame is directly related to the kinetics of the reaction, as admitted above, isn't it true then, that the production can be estimated by multiplying the production from micrometer-scale particles with the ratio of their surface area to that of the molecules formed from plasma? --James S. 17:59, 26 February 2006 (UTC)

No. Physchim62 (talk) 22:50, 26 February 2006 (UTC)

On the contrary, sublimation is a surface reaction. Moreover, O₂ pressure increases the chance of formation. --James S. 06:53, 27 February 2006

Two kinds of pressure

The maximum pressure at which a spectroscopic signal may be drawn has no relation to the maximum pressure at which a reaction occurs. --James S. 01:44, 3 March 2006 (UTC)

This is just gibberish, with no relation to the issues under discussion. --DV8 2XL 02:51, 3 March 2006 (UTC)

Why do you say so? You have also claimed that a description of the bond angles and length is unrelated to molecular structure. Why? --James S. 03:00, 3 March 2006 (UTC)

Where have I claimed this? --DV8 2XL 19:31, 3 March 2006 (UTC)

You removed my description of the bond angles and lengths from Uranium trioxide. Why? Please also address why you think that an early 1960s-era spectrograph's maximum pressure for a signal might be related to the observed reaction's maximum pressure. Do you deny that sublimation is a surface effect? Do you deny that the chance of UO₃(g) formation increases with O₂(g) pressure against U₃O₈? --James S. 03:03, 5 March 2006 (UTC)

Aerial combustion product of uranium section from Uranium trioxide

Gaseous monomeric UO₃ is produced by combustion of uranium metal in air from 2200-2800 Kelvin (Ackermann et al. 1960; Mouradian et al. 1963.) The production of UO₃ gas vapor is "not infrequently ignored" (Gmelin vol. U-C1, p. 98). UO₃(g) molecules condense.

Uranium trioxide gas molecules are a known intermediate in the chemical transition reactions forming U₃O₈ crystals from combustion products including uranium oxides. According to Wilson (1961), Ackermann et al. (1960) show that U₃O₈ crystals result from the two step process:

¹/₃ U₃O₈(s) + ¹/₆ O₂(g) → UO₃(g) at T₁;

UO₃(g) → ¹/₃ U₃O₈ + ¹/₆ O₂(g) at T₂;

where T₂ < T₁.

Individual UO₃ gas vapor molecules will not decompose below the burning temperature of uranium in air, because uranium monoxide requires additional energy to form, as does the release of O₂ by a single UO₃ molecule. (Hoekstra and Siegel 1958; Wanner and Forest (2004) p. 98.)

Uranium-nitrogen salts UN_x, where x usually is one, form above 800 degrees Celsius. S. Cotton (1991) Lanthanides and Actinides (New York: Oxford University Press) also writes, on page 127: "Aerial oxidation of any uranium compound eventually results in the formation of a uranyl compound."

I wish I had remembered that Simon Cotton reference a month ago. --James S. 08:20, 17 March 2006 (UTC)