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Chemosynthesis
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Quote: Originally posted by elementcollector1  | | If this is anything like the chloride, the NH4F decomposes into NH3 and HF, which are both hygroscopic. Given enough starting
NH4F, this should remove all the water from your chloride, rendering it anhydrous. |
This is valid, just as with the chloride.
I don't have this in hand, but check out J. Chem. Phys. 37, 2311 (1962); http://dx.doi.org/10.1063/1.1733003
I am interested in adopting that article and J. Inorg. Nuc. Chem., 1962, Vol.24, pp. 387-391 for another project.
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blogfast25
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Pyrolysis of NH4ThF5 === > ThF4 + NH4F
The NH4F fumes off, like NH4Cl does, leaving behind the dry ThF4. The NH4ThF5 is obtained by dissolving freshly precipitated Th(OH)4 in hot,
concentrated NH4HF2,
The ZrF4 will be for a magnesiothermic reduction.
[Edited on 12-4-2014 by blogfast25]
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Dan Vizine
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How is the ammonium zirconium fluoride decomposed? Or, more specifically I guess, what is the reactor made of?
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Lambda-Eyde
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I'm surprised to see this hasn't been posted yet (I think?). Pleased to see you're back, Dan/Zan. Looking forward to reading more.
Attachment: Production of Thorium Powder by Calcium Reduction of Thorium Oxide.pdf (159kB)
This file has been downloaded 1329 times
This just in: 95,5 % of the world population lives outside the USA
You should really listen to ABBAPlease drop by our IRC channel: #sciencemadness @ irc.efnet.org
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Dan Vizine
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Thanks for this incredibly useful reference.
My Th will have several hundred ppm Ni, I see. Not a major concern. If I end up at >99% I'd be ecstatic, and quite satisfied @99% and not at all
disappointed if I break 98%. These are modest goals given past work.
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Dan Vizine
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Say hello to my little friend.
[img] [/img]
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elementcollector1
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You stop that. 
[Edited on 4-16-2014 by elementcollector1]
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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annaandherdad
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Hi, Dan, just a couple of things about thorium. If your supply has been sitting around for a few years since it was prepared (thorium nitrate in your
case), say 10 or 15, then it will have an equilibrium population of the entire chain of decay products. This is quite unlike uranium, which requires
thousands of years to reach equilibrium. The bottleneck in the case of thorium is radium 228, with a half-life of about 6 years.
So if you transform your sample of thorium chemically, in particular, if you do anything to purify it, then you will be throwing away all the daughter
products, some of which are interesting. For example, you could repeat what Curie did with uranium, by isolating radium; the difference is that your
isotope of radium has a 6 year half-life, so its activity will gradually disappear on a human time scale. Another interesting isotope is radon 220,
with a half-life of less than a minute. It gives some spectacular effects in a cloud chamber, see the youtube video on this by bionerd23 (https://www.youtube.com/watch?v=Efgy1bV2aQo), which is one of the coolest scientific videos I've ever seen. But to get this radon, you must start
with thorium that has been left undisturbed (not purified chemically) for roughly 5 or more years.
Actually, I have to correct that. If you take a sample of thorium that has been sittiing around for a long time and purify it chemically, you'll get
a mixture of thorium 232 and thorium 228, the latter of which has about a 1 year half-life. So the small amount of thorium 228 will start its decay
chain, and produce some radon after a while. But this will only last a couple of years.
As for radium, if you separate that chemically, you actually get a mixture of two isotopes, one with a half life of 6 years, the other only a few
days. So after such separation, the activity will drop by 1/2 over a few days; then over a year or so it will build up again as the equilibrium decay
chain is established, this time starting with radium 228 (here the bottleneck is thorium 228).
I bought some thorium nitrate with the intention of using it to get some radon 220 as in bionerd23's demo, but I'm thinking better of it now. If
you'd like to have it I'd be glad to give it to you (I think you'd have to be in the US).
Any other SF Bay chemists?
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Dan Vizine
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Since the cost of materials acquisition has to stop somewhere, I will not have instruments appropriate to measure the emanations from my sample.
Heretical as it may sound, I will gladly forego radium. Everybody draws the line somewhere, mine tends to be about where I can no longer assess the
dangers. Polynitroalkanes, pyrophorics, potent alkylating agents, liquid HCN, etc. Bring 'em on. Things of microscopic size that I can't detect but
that are as dangerous as Ra, that's a whole 'nother story as they say.
I'd rather isolate a pound of ricin (NOTE: G-man, this is just an example, so if your software found my ricin remark, rest easily.) than isolate 10 mg
of Ra.
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annaandherdad
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Yes, I think you're right, you wouldn't want to do this without a geiger counter. But I might say the same thing about your project for production of
thorium metal. You're going to have those decay products in your sample of thorium, and if you do anything to purify the thorium chemically, such as
making thorium metal, the decay products are going to be there in your waste.
The thorium decay chain is *much* more favorable than the uranium chain, insofar as the danger of the decay products is concerned. You'll have
radium, all right, but it will be nanograms, not milligrams. Also, unlike the radium isotope you get from uranium, this one has a half-life of only 5
years.
In equilibrium, which you will probably have with your thorium sample, the total activity (in Bequerels) of each of the decay products will be the
same as that of your thorium. In other words, the amount of radium will be so small that the number of decays you get from it will be the same as
from your thorium. Given the long lifetime of thorium (1.4 x 10^10 yrs), a mole of thorium will have maybe 10^6 Bequerel. The radium in the decay
products will have the same activity.
Any other SF Bay chemists?
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Dan Vizine
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Annaandherdad,
It's midnight and I'm heading to SF in the morning. I very much appreciate the content and intent of your remarks and I want to continue this
discussion as soon as I can find the time to do it justice.
Dan
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annaandherdad
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I've been thinking about the chemistry of the thorium decay chain for some time, but haven't done anything because of various worries (not only mine,
but my wife's too). But maybe I will, some day. In the meantime, you might be interested in some of my reflections on the subject.
First of all, to put the radioactivity of thorium into perspective, Th232 has a half-life of about 1.4x10^10 years, or a 1/e life (the "lifetime") of
this divided by ln 2=0.7, or about 2x10^10 years = 6 x10^17 sec. This means that a mole of Th232 produces about 10^6 decays/sec, due to the initial
decay Th232->Ra228. This is 10^6 Bequerel/mole, or roughly 4000 Bequerel/gm. This compares to natural potassium (with it's .01% of K40) that has
an activity of 35 Bequerel/gm.
The actual activity of a sample of natural Th is 10 times as much as this, because of the decay of the daughter products. Measuring activity in
Bequerel gives just a rough measure of the radiation, because the different decays are of different types (alpha, beta, gamma), and have different
energies. For example, the decay Ra228 -> Ac228 produces a beta particle (electron) with quite a low energy. But measuring activity in Bequerel
is at least a place to start in thinking about the radioactivity.
If you chemically purify natural thorium, you will get a mixture of Th232 and Th228, with one atom of Th228 for every 7x10^9 atoms of Th232. This
number is the ratio of the half-lives of the two isotopes (1.4x10^10 years vs 1.9 years, my data comes from the wikipedia article). The total
activity of thorium prepared in this way is twice the activity of pure Th232, that is, about 2x10^6 Bequerel/mole, because both the Th232 and Th228
produce the same rate of decay. As time goes on, however, the activity will increase, as the daughter products are created and start decaying
themselves. Of course, no one prepares pure Th232, because there is no point in separating the isotopes and it would be a lot of trouble.
If you wait long enough, such a sample of thorium, chemically purified at t=0, will produce 10 x the activity of pure Th232, that is, about 10^7
Bequerel. This is the same activity (in Bequerel/mole of Th) that you would see in a sample of thorium ore, that did not contain any radioactive
substance apart from the thorium decay chain. Here "long enough" means several multiples of 5.7 years, the half-life of Ra228, the daughter product
in the thorium chain with the longest lifetime, and the factor of 10 comes from the fact that there are 10 radioactive daughter products of Th232. In
equilibrium, every daughter product produces the same activity (in Bequerel), and the molar fraction of each daughter product is the ratio of the
lifetime of Th232 to the lifetime of the daughter. So, for example, in such a sample, the number of moles of Ra228 would be 2x10^9 times less than
the number of moles of thorium, and, of Ra224, you would have 1.4x10^12 times less. These ratios again are the ratios of the lifetimes. Ra228 and
Ra224 are the two isotopes of radium that occur in the thorium decay chain.
One conclusion from all this is that if you're not afraid of the radiation from a sample of thorium, you shouldn't be afraid of the radiation from the
daughter products. Of course, you have to be aware of the types of radiation involves, and physical characteristics (radon is a gas, etc).
The two most interesting things to do chemically to a sample of thorium are to separate the thorium from its daughter products (purify the thorium),
and to separate the radium. The other daughter products have lifetimes that are too short to make chemical separation very interesting. Presumably
you could separate the radium by precipitating the sulfate. I assume radium sulfate is even less soluble in water than barium sulfate. The actual
quantities of radium are very small, so one could worry about whether the radium sulfate might remain in solution (say, after adding sodium sulfate to
a solution of thorium nitrate), that is, in spite of the low solubility, since the molar fraction of radium is so small. I'm not too sure about this,
but I had the impression for discussions on this forum earlier that if one added some barium nitrate, and then precipitated the sulfate, that the
radium sulfate would precipitate along with the barium sulfate. Of course, the Curies did something like this in their work, and it would be useful
to learn in more detail what they did.
The radium produced in this way would be a mixture of the isotopes Ra228 and Ra224. It would have less activity than the original sample of thorium
(because the other daughter products and the thorium itself would have been rejected), but it could be much more concentrated. Practically speaking,
in a home lab you'd be talking about nanograms of radium mixed in with milligrams (at least) of barium.
Now would this be a horribly dangerous thing to keep around your home? Not if you measure it in terms of total activity; it would be less than the
activity of the thorium you started with. Only the concentration would be different. You could contaminate your lab if you spill it, but, again the
total activity of the contamination would be about the same as that of your original thorium, and, in any case, the radium activity would decay with a
half-life of about 5 years. Obviously you wouldn't want to wait 50 years to use your lab again (to wait for the activity to decrease by a factor of
1000), but at the same time it's not like you're running a danger of contaminating your entire neighborhood for a million years.
This is quite different from what you'd get (following the Curies) if you separated the radium from natural uranium, because that isotope of radium
has a half-life of 1600 years. I read somewhere that Marie Curie's cookbooks (that she used at home) are so radioactive that they have to keep them
in a lead box. And they will have to continue to do so for a long, long time.
I was interested in separating the radium for the purpose of producing radon. More about radon later.
Any other SF Bay chemists?
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Dan Vizine
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Judging from the physical characteristics of the bottle, which include the old Fisher embossed cap, the font used in their certificate of analysis,
the look of the label material and other indicators, this bottle is probably at least 40 years old. Old enough to guarantee that we are talking about
material with an activity on the order of 10exp7 Bq/mol. So, 1 pound of the tetrahydrate represents about 8.2 x 10exp6 Bq.
I'd like to look at this in comparison to the ICRP occupational radiation exposure guideline which is 50 mSv/yr. Unfortunately, it's difficult to
find a figure* for the number of nanoSv per unit time per Bq internalized (committed effective dose equivalent) for thorium nitrate. Although it's
surely going to be lower for the nitrate that the dioxide, right now I don't have any idea what the rough magnitudes are. Maybe it would be
instructive to just to do the calculation with the value quoted for K 40 which is five nano Sieverts over 50 years per Becquerel ingested just to
ballpark it? I realize that the K value is for ingestion, whereas the thorium daughters will be primarily inhalation dangers so this has limited
value...maybe very little....
(5nSv/Bq) (453 g) ( 4 x 10exp4 Bq/g) = 91 x 10exp6 nSv = 91 mSv = 9.1 rem/year. A bit less than twice the 5 rem/yr that ICRP allows. All in all, if
the 5nSv/Bq isn't wildly divergent for my material (I'll look more), the risk for simply standing next to the contents of the bottle is acceptable.
After that, it's all a matter of chemical hygiene (mostly).
With regard to the radium sulfate, just as you surmised it has somewhat lower solubility than barium sulfate in keeping with periodic trend. However
the solubility, just taking your nanograms figure at face value, wouldn't exceed the solubility product constant with the volume of solution that I
will have.
One of the more potentially challenging aspects will be adequate cleanup. Just one of several examples....there are many steps where metallic thorium
is being triturated in water. The water from the washes, which is decanted (prior to filtration), contains the fines that have proven troublesome
(fires, explosions) for experimenters to dispose of due to the nature of very finely divided thorium. I probably will not try very hard to capture
this material for reprocessing. More likely I will simply solidify it with concrete.
*I take that back. It was easier than I thought. Now to try and decipher it....
[Edited on 2-5-2014 by Dan Vizine]
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MrHomeScientist
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So many damn units for radiation, and I've never been able to figure out how to convert between them or what any really means. I have similar problems
with the million ways to express gas pressure. 
Anyways best of luck preparing thorium! I've been reading this thread with excitement. The closest I'll probably come is obtaining thorium oxide from
thoriated welding rods - I already bought the rods, and there's a couple methods outlined on the forum. I briefly considered a "thorium thermite"
using the oxide, but even if that is possible thermodynamically it sounds like a pretty horrifying radiation risk.
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Dan Vizine
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The units of radiation dosage are enough to make your head swim. It's so damned much work just to wade through.
Speaking of hypothetical thorium thermite, my primary concern is avoiding airborne everything. I am still kicking myself for missing the ThO2 that was
on eBay. Now I have to be concerned about radon trapped in the crystal lattice when I dissolve the nitrate, the residual ThO2 that will remain in
sintered glassware, and the problematic drying of the precipitated ThO2. The last one is the worst. Think about it. How do you best dry a water moist
material without millions of microscopic pops creating a certain amount of dust? It has to be absolutely dry. So dry that I can calcine it at 800 C
for 8 or 10 hours prior to reaction. If you don't, adsorbed CO2 ends up as C in the product.
Then, after the reaction completes, I need to break the reaction cake into pea-sized pieces and hydrolyze them by throwing them into water, where the
unreacted Ca will bubble and spew. I need to watch the temperature so as to avoid the re-oxidation of Th. At this point, things become easier.....
Anyway, thanks for the well wishes. This will undoubtedly take a while to play out. I kind of picture setting a lab up outside in the warmer weather.
Since I live in the Buffalo area, that probably means June.
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The Volatile Chemist
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Side Note: Could you separate out different isotopes of thorium, or other many isotoped elements, by electrolysis, like they do for water? Higher
isotopes less likely to be electrolyzed first?
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Dan Vizine
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No, the kinetic isotope effect is large enough for H/D to do this, not for larger atoms. Also, for H/D there is a mechanism to remove products out of
the reaction mixture that you wouldn't have for a metal.
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The Volatile Chemist
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| Quote: Originally posted by Dan Vizine | | No, the kinetic isotope effect is large enough for H/D to do this, not for larger atoms. Also, for H/D there is a mechanism to remove products out of
the reaction mixture that you wouldn't have for a metal. |
So the method wouldn't even work for odd isotopes of lithium...? huh.
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Dan Vizine
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The % by which they vary in weight becomes small quickly. But even if it could work in principle, you still have the real world problem of separating
the product.
It works well for water + heavy water because of two reasons. The first is that the isotopes differ greatly (% wise) in mass. But the second is just
as important. When you electrolyze water the products leave as gasses. How are you going to do that separation cleanly with a high temp. lithium cell?
Of course, that's not to say the alternative is clean either.
Li-6 and Li-7 were traditionally separated (enriched is more accurate) by multistage distillation. A single stage isn't nearly enough though, because
the masses are close. The difficulty in separating these nuclear species, together with the incorrect assumption that Li-7 wouldn't fuse, led to a
disastrous "Hydrogen" bomb test in the Pacific called "Castle Bravo". We expected 4 or 5 Mt and got 15 Mt by mistake. That remains the largest nuke
the US ever detonated.
[Edited on 3-5-2014 by Dan Vizine]
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annaandherdad
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I found an old article on the solubility of radium sulfate (attached). It is very interesting. The most interesting points are these:
1. When precipitating radium as a sulfate from a mixture containing radium and barium (with the barium typically in great excess), the fraction of
radium in the precipitate is the same as it was in the solution.
2. The solubility of radium sulfate does not follow the law of mass action, in other words, there is no equilibrium constant. In particular, the
solubility of radium sulfate in water and in dilute sulfuric acid of various concentrations is about the same, whereas the law of mass action would
predict a massive suppression in the solubility of radium sulfate in the presence of sulfate ions. The article does not discuss other situations of
interest, such as the solubility of radium sulfate in solutions of sodium sulfate, nor does it provide more than speculation as to why the law of mass
action is not followed.
3. The solubility of radium sulfate at 25C in water is 8.2x10^-8 gm/cc (the units they used). In view of point 2 above, there is no point in trying
to calculate an equilibrium constant.
The article is an early one on the subject, and no doubt a lot of later research has been done. The article leaves a lot of questions unanswered.
But for me the main point is that if one wanted to precipitate radium from a sample of thorium (say, thorium nitrate), it could be done with high
efficiency by adding some barium salt and then some dilute sulfuric acid.
Probably someone on this forum has knowledge that goes way beyond what I know or what is in this article; I'd be glad to hear any good information.
Attachment: Lind.Underwood.Whittemore.JACS.XL.465.1918.pdf (524kB)
This file has been downloaded 618 times
Any other SF Bay chemists?
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annaandherdad
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The units of radiation exposure are certainly confusing. I haven't tried to study them in detail, because the details involve various fudge factors
to convert energy deposited into an equivalent biological effect. But before the fudge factors are applied, one is talking about energy deposited per
unit mass of tissue. So a Sievert is one joule/kg (then adjusted by fudge factors), and a rem is 100 ergs/gm (again, adjusted). 1 Sievert = 100
rem. The annual exposure that people get from natural sources (cosmic rays, radon, etc) is about 300 millirem/yr (3 milli Sievert), as I recall from
the days when I worked in radiation, and you maybe double this from medical procedures.
I've been looking at an article on the internal radiation exposure to the human body. This is it:
http://sciencedemonstrations.fas.harvard.edu/icb/icb.do?keyw...
I've been playing with the numbers in this article. They are measuring the gamma rays produced by K40 decay in a human body. They estimate 140g of K
in a human body of 70kg, the nominal value they use. Due to the content of K40, this translates into 4,400 Bequerel (they cite this as 266,000 decays
per minute). The say that 89% of the decays are beta decays with a maximum energy of 1.33MeV. When I work this out, it comes to 8.4x10^-10 J/sec =
1.2x10^-11 J/kg-sec, assuming 70kg body, which is 3.6x10^-4 J/kg-year, or nominally 36 millirad/year. But the article quotes the value of 16
mrad/year. Now I believe the rad is 100ergs/gm, before any biological effect fudge factors are applied. But the article says that the beta decays of
the K40 exposes the human body to only 16mrad/yr. So did I make a mistake? Maybe the difference is accounted for by the fact that the 1.33MeV quoted
is the *maximum*energy per beta decay; since some energy is carried off by the neutrino, the *average* energy deposited in the tissues would be less,
maybe bringing the number down to 16mrad/yr. I'm just guessing about this.
Anyway, if I do the same type of calculation for thorium, adding up all the energies of all the 10 decays of the 10 daughter products, I get 6.8x10^-6
J/sec-mole, or in a 70kg body (assuming you ate a mole of thorium), you'd have 9.7x10^-8 J/kg-sec-mole, or 0.29 J/kg-year-mole, or 0.29
Sieverts/year-mole (unadjusted for biological fudge factors), or 29 rad/year-mole. This is a lot more radiation than you'd want to get in a year, but
then you probably wouldn't be eating a mole of thorium.
One could work harder on these numbers and get some better estimates. Given that the starting point is energy deposited per mass of tissue, obviously
there is no effect if no energy is deposited. A lot of the energy released by thorium and its daughters is alpha radiation, which won't deposit any
energy into your body if you don't eat it or breathe it.
Any other SF Bay chemists?
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annaandherdad
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Found this article on thorium deposits in the US. I go back to the area in North Carolina where there are placer deposits of monazite, but I never
knew they were there.
http://pubs.usgs.gov/circ/1336/pdf/C1336.pdf
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The Volatile Chemist
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Wow on the thorium deposits! I doubt there's anything radioactive in Ohio, but I go with my family to the Carolinas every so often... Is there a
section of SM just for gaining hard-to-find regents from deposits? There should at least be a post for it -- I'll look.
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annaandherdad
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Yes, and it looks like monazite is a good source of rare earths, too. See:
http://en.wikipedia.org/wiki/Monazite
Given the interest in rare earths, makes me wonder if someone is looking anew at those placer deposits. I'm also wondering if it's possible to go out
there with a pie pan and pan for thorium, without getting shot at, I mean.
Any other SF Bay chemists?
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annaandherdad
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Another article on thorium production and consumption in the US:
http://minerals.usgs.gov/minerals/pubs/commodity/thorium/690...
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