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Radium

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gerontius grumpus
34833.  Sat Nov 26, 2005 10:07 am Reply with quote

Forgive me for being pedantic and picky but I don't think radium is luminous (QI 25/11/05). The radioactive luminous paint referred to contained radium and a fluorescent phosphor such as calcium tungstate.

Radiation from the radium causes the phosphor to emit light.

I don't know how ready brek luminescence works though.



PS. Sorry about all the growling, I keep forgetting to untick my signature.

 
JumpingJack
34844.  Sat Nov 26, 2005 10:32 am Reply with quote

I fear you are mistaken, gerontius.

The luminous paint referred to contained only 70 micrograms of radium per gram but was still enough to trigger cancerous growths in the mouths of the girls who licked their paintbrushes.

However, according to "Nature's Building Blocks: An A-Z Guide to the Elements" by Dr John Emsley (OUP, 2001) radium itself is indeed luminous.

Discovered in Paris in 1898 by Pierre and Marie Curie:

Quote:
They named the element radium after the rays (radii) of faint blue light with which it glowed in the dark. In the words of Marie Curie:

"One of our joys was to go into our workroom at night when we perceived the feebly luminous silhouettes of the bottles and capsules containing our products. It was really a lovely sight and always new to us. The glowing tubes lloked like fairy lights".


The glow is caused, apparently by the radioactivity of the element exciting the surrounding air.

 
gerontius grumpus
34874.  Sat Nov 26, 2005 11:15 am Reply with quote

Perhaps we can find some middle ground here:

It was the radiation (gamma rays) that "triggered cancerous growths in the mouths of the girls who licked their paintbrushes",
not the light.

"The glow caused by the radioactivity of the element exciting the surrounding air" came from the surrounding air, so the air is the phosphor in this case.

Radium stored in glass tubes would also cause the glass to fluoresce in the same way that the glass of Roentgen's rarified gas tubes were seen to fluoresce when energised.
in this case the glass is acting as the phosphor.

It is also quite likely that impurities such as quartz and other minerals in the samples would show fluorescence.

Also radiation from nuclear fuel stored under water causes the water to fluoresce.

I think it is highly unlikely that the faint fluorescence in the air or glass would produce enough light for luminous dials if the radium content was so low. The whole point of a phosphor is that it converts the energy of each Photon of gamma radiation into many more light photons.

Air is a very inefficient phosphor and because of the inverse square law, only the air in immediate contact with the radium would produce sufficient light to be visible.

If the concentration of radium in the paint was high enough to generate visible light without a specific phosphor (i.e. just by excitation of air and impurities) then the girls would have suffered non-stochastic effects such as radiation burns, sickness and erythema, long before any cancerous growths appeared.

 
JumpingJack
34907.  Sat Nov 26, 2005 11:59 am Reply with quote

Well now, I must say, I think you're really splitting hairs.

I didn't (or rather Dr Emsley didn't) claim it was the luminosity that triggered the cancer. Only the radium. And it's radioactivity, natch.

Radium glows in the dark or causes the glass in which it is stored to glow in the dark. This is a fine difference indeed. The point is that the reason why the Curies called it radium is that they observed it to emit visible rays. To me that means luminosity.

Perhaps your science is better than theirs and you know the actual reason why this happens. But it sounds to me as if you're guessing.

Nor did I (or Dr Emsley) say that it was the radium in the paint that was producing the glow on its own. He doesn't give details of the other constituents of the paint and I'm quite happy to accept that it was the radium's reaction with another substance that caused the paint to be visibly luminous.

I think if you want to nit-pick at this level of detail, I think you owe it to me to read my posts with a bit more care.

 
JumpingJack
34911.  Sat Nov 26, 2005 12:02 pm Reply with quote

In the nicest possible way.

 
Rory Gilmore
34931.  Sat Nov 26, 2005 12:41 pm Reply with quote

Another point is that despite the evidence given, the theory about swimming through syrup (suggested by one of Newton's rivals) was brought up and proved wrong on Brainiac: Science Abuse where swimming in water took only a fraction of the time swimming in syrup did. Maybe this failure lies in the fact that whilst you can push back harder in theory, you may just be too lazy.

 
samivel
35148.  Sat Nov 26, 2005 4:48 pm Reply with quote

Or they used a thicker syrup

 
ficklefiend
35197.  Sat Nov 26, 2005 7:26 pm Reply with quote

samivel wrote:
Or they used a thicker syrup


Yews, brainiacs are notorious for their complete disregard of constants in experiments *sighs a scientist sigh*

I like rough science best, there is something brilliant about how it manages to portray the scientists as very clever but not pretentious.

 
djgordy
35198.  Sat Nov 26, 2005 7:32 pm Reply with quote

ficklefiend wrote:


I like rough science best, there is something brilliant about how it manages to portray the scientists as very clever but not pretentious.


I like Rough Science too. But then I've got the hots for Kathy Sykes and Kate Humble!

 
Flash
35201.  Sat Nov 26, 2005 7:47 pm Reply with quote

I've posted elsewhere about the University of Minnesota project which we quoted, and how it seems to me to be a better source than Brainiac.

 
JumpingJack
35251.  Sat Nov 26, 2005 10:42 pm Reply with quote

Kathy Sykes is wonderful.

There is a question based on her briilliant work at AtBristo in the QI DVD ...priced at 18.99 inc postage and packing and available at the QI online bookshop!!

 
laidbacklazyman
35294.  Sun Nov 27, 2005 6:04 am Reply with quote

JumpingJack wrote:
Kathy Sykes is wonderful.

There is a question based on her briilliant work at AtBristo in the QI DVD ...priced at 18.99 inc postage and packing and available at the QI online bookshop!!


Is that a nylon wig, kipper tie, and K-Tel Top of the Pops with Pans people advert I see before me?

 
JumpingJack
35296.  Sun Nov 27, 2005 6:13 am Reply with quote

The very same, lblm.

The global marketing push for this coveted item is gathering pace.

The QI guerilla viral publicity machine powered into Wantage yesterday and cunningly moved WH Smith's entire stock of QI DVDs* from the bottom shelf near the fire exit to the Two-For-26.99 bestseller rack by the front door.

Expect a massive lift in sales.





*both of them

 
laidbacklazyman
35301.  Sun Nov 27, 2005 6:36 am Reply with quote

selling lifts as well as books and DVDs now.

You want to get either these people or this lot on your team, they work wonders

 
gerontius grumpus
35302.  Sun Nov 27, 2005 6:38 am Reply with quote

Anyway, back to the subject of Radium:

Radioluminescent paint contained Radium226 with Zinc sulphide as the phosphor.
Radium 226 emits alpha particles at 4783.34 keV and 4601 keV
and gamma rays at 186 keV.

I have been unable to find an energy value for the light emitted by zinc sulphide, but visible light is in the range of 2 to 3 eV.

It is therefore quite clear that even with the inevitable energy loss in conversion, the intensifying power of the phosphor is huge.

Yes I might be nit picking, but what else can I do when I am told I am mistaken?

 

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