Originally posted to Quora, written by Carl Willis
Uranium gets a bad rap, being widely regarded as exotic and dangerous. As a fellow "amateur chemist" (more recently, career nuclear engineer)
experienced with uranium, I would like to challenge this unfairly negative reputation and suggest that you CAN study the "household chemistry" of
uranium safely and responsibly without resorting to a poor surrogate. A basic working knowledge of inorganic chemistry is a prerequisite to a
satisfying experience; that is true of all chemistry. So be comfortable with stoichiometry, balancing equations, measuring mass and volume, etc. Be
comfortable with prevailing standards of chemical hygiene and safety, like wearing gloves and eye protection. The big dangers here are the same
mundane ones you'd find in high-school intro chemistry: strong acids and bases, hotplates, flammable solvents. Although a toxic heavy metal, uranium
is far more approachable than, say, arsenic or mercury or fluorine chemistry in a residential setting. The keys to good hygiene and responsible use
lie in working with small quantities (think about containing the mess if a container were to break or fall over) and controlling waste generation. Buy
some microscale glassware. Just be aware that if you work with large (~kg) quantities, or plan to sell or transfer things you make to other people,
you are no longer an inconsequential "hobbyist" and will find yourself up against the strictures of your jurisdiction's nuclear regulatory framework,
which in the USA is the domain of the Nuclear Regulatory Commission. The NRC defines, and subjects to a general license for use, "small quantities of
source material" below 1.5 kg; see 10 CFR 40.22. So if you play around with some introductory uranium chemistry, start small (with a couple grams of
material) to avoid the prospect of a soul-crushing run-in with regulators.
How to obtain uranium: You have two choices. First choice is to buy uranium on eBay, where there are regular sellers of compounds like uranyl nitrate
and oxide. Depending on your focus, you might be interested to know if your uranium source is "depleted" (low in the U-235 isotope) or "natural"
(0.72% U-235). Typically, commercial uranium compounds are made from depleted uranium (cheaply available from the nuclear fuel industry), while those
prepared from uranium ore directly are natural. Your second choice is to refine uranium from a concentrated ore specimen. This process is not
difficult (see my website link below), but it does generate a lot of waste that can't be put down your drain.
Basic chemical overview: Aqueous uranium chemistry is dominated by the uranyl ion (UO2)2+, with U in the U(VI) oxidation state. This is a
brightly-colored, greenish-yellow, UV-fluorescent species. Uranyl compounds are generally soluble in acids, and precipitate as marginally-soluble
yellow to orange uranate and diuranate salts with alkalis. Uranium in its lower (IV) oxidation state is sometimes encountered in the form of the
dioxide UO2 and the green tetrafluoride, UF4. These compounds are not appreciably water-soluble and in order to dissolve uranium in these forms, it
must be oxidized to (VI) with an appropriate reagent. Uranium metal is very hard to prepare in small quantities and you will probably not get an
opportunity to buy it in metallic form either.
Suggestions for chemistry of interest: Uranium is unusual chemically in a few respects. Consider its nearly-insoluble peroxide: no other
naturally-occurring elements have an insoluble peroxide at acid pH. Uranium forms some commercially-interesting complexes, like the uranyltricarbonate
anion (which is soluble in basic solutions, in which most transition metals precipitate) and the uranyl nitrate-tributyl phosphate complex (which
forms the basis of liquid-liquid solvent extraction of U and Pu in nuclear fuel reprocessing), and a peroxo complex that is vivid blood-red. You can
play with this chemistry at home because the other chemicals needed are ordinary. TBP has to be ordered from a chemical supplier, but you shouldn't be
given trouble for it. Uranium offers interesting opportunities for radiochemistry. Prepared uranium--depleted or natural--quickly builds up an
equilibrium concentration of U-238 decay daughters Th-234 and Pa-234. These are beta- and gamma-emitting nuclides, whereas the parent U-238 only emits
alpha particles. Thus, it is fun to see in any given chemical experiment with uranium if the apparent activity (on a common beta-gamma sensitive
Geiger counter) follows the uranium itself or not. Freshly-purified uranium compounds will seem minimally radioactive, but after a couple months Th
and Pa are back in the uranium! The waste from re-purifying daughter-contaminated uranium compounds may be left around to decay, and will exhibit the
easily-measurable half life about about three weeks due to the Th-234.
My own background: see my blog posts about household uranium chemistry here: http://carlwillis.wordpress.com/...
Dabbling in uranium chemistry is fun for the whole family, educational, and it ain't gonna kill you or the neighborhood as long as common sense
prevails.
Below: uranium compounds made by safe and responsible household techniques. See website for details.
Posted by Carol Willis on Quora.com |
