Mystery metal

Yea - I know - only 0-5 R/h - need mR and uR scales for real work. At least the 0-5 does function - and isn't at zero. Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Nick Hull wrote:

Any logical explanation for why radioactive glass (I presume thats where the radioactivity was) would be better optically? Seems odd. The radioactivity can't matter by itself can it?

Index of refraction. more power in a flatter lenses or even more in a curved one. Size (diameter) is light gathering ability. Focal length determines magnification. They wanted more magnification without getting larger.

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

xray wrote:

Thorium oxide based glasses have a very different combination of refractive index and dispersion than other glasses available at the time, allowing better correction of optical abberations.

Thorium is only very slightly radioactive, and the health problems were psychosomatic, not physical, for users of the resulting optical systems. Manufacturers had to be more careful, as they were exposed to the dust resulting from grinding lenses.

Joe Gwinn

Not so sure - as it is a high Alpha emitter - used in Vacuum tubes for massive currents - with a very long lifetime. TH 232 is close to the famous U 238 isolated by 1 element called Protactinium. By the way - U is an alpha source also.

The Alpha emitters can cause eye damage. You state it was all a mental illness. I think that was bad science running rough shod over victims. Just like agent orange and .....

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Joseph Gw> >

Thorium is (perhaps was?) also found in gas mantles, for those camping lamps.

Dave

The half-life of Thorium is something like ten billion years, so the radiation is very dilute -- every so often, a thorium nucleus goes POP.

I don't know how one would achieve eye damage with thorium-bearing glass. I suppose one could hold the lens against one's eye for a million years. But the thorium-bearing lenses were typically used only within the optical system, because this glass was too easily scratched.

Cosmic rays are by far the larger radiation source. If one flys from LA to NYC, being above most of the atmosphere and its shielding, one gets a

Fear of radiation from thorium-bearing glass lenses in an optical instrument is therefore a mental issue.

The real danger was that people grinding lenses from thorium-bearing glass for a living would ingest a lot of the dust, and would be irradiated from within. Even that danger wasn't very large, as the dust passes right through largely unaffected. But there are many reasons to avoid ingesting glass dust.

Lens grinding is always done wet (using water), which already controls the dust. One can still use thorium-bearing glass, but the required manufacturing safety precautions and swarf disposal regulations are such that people use other kinds of glass these days, kinds of glass that were not available back when. I don't know if one can still buy the thorium-bearing glass in the West. The Russians probably still make it.

Joe Gwinn

Still is as of 5 years ago or so; I tested a new one and it's detectable.

Alpha emitters can cloud and kill eye tissue that is right next to the glass. I heard it was more than alpha in the first place. And transversing to the retina via the carrier fluid.

Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Tom Miller wrote:

I have some - gave off more white light. Now they don't use it.

Thorium is the reason why soft coal power plant is more radioactive than a Nuke plant. Thorium is found in soft coal.

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

snipped-for-privacy@yahoo.com wrote:

Also in most clay bricks.

Just don't visit the mountains - more than alpha is in the rocks there!

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

Tom Miller wrote: