[ExI] Ants to spike

Brent Neal brentn at freeshell.org
Wed Oct 21 17:16:25 UTC 2009

On 21 Oct, 2009, at 12:02, Eugen Leitl wrote:

> On Wed, Oct 21, 2009 at 11:47:29AM -0400, Brent Neal wrote:
>> Clearly, you've never used an XRF. :) Less than 2 minutes of sample
> I have. I just don't have one in the house right now. Can I borrow  
> yours?

You need to schmooze the grad students more. :)  Certainly, if there  
is a quick, dirty chemical analysis, you can get your instant  
gratification. But even with something as simple as the lead  
precipitation, if you don't have nitric acid laying around, you're  
going to struggle.  It all depends on what you have going for you and  
who you know. Most ppl don't have a CNC machine, but if you need to  
get things milled, I'd bet you that you've made friends with someone  
who owns/works at a machine shop.

You could also build your own XRF - in principle, all you need is an x- 
ray tube, a photomultiplier tube, and some monochromator optics. If  
you really wanted to gild the lily, you could get a bell jar, and a  
tank of helium.

>> prep (load powder or flak into PP vial) and about 2 minutes of scan
>> time. Look for lead peak. Done. XRF is widely used in industry for
>> quick assay, especially in environmental analyses.  Just cause its
>> "instrumentation" doesn't make it complicated! Spectroscopy is well-
>> accessible to a citizen scientist.
>> Also, you need more than eye for lead chromate, because how will you
>> tell it from other blue pigments?
> That's because if it's an old house with oil paint which looks
> like this http://images.google.com/images?q=lead chromate
> there aren't too many options.
I agree that looks distinct. However, I'm not sure if I'd trust my  
aging eyeballs to distinguish a small chip with lead chromate from  
some cobalt compound. :)


Brent Neal, Ph.D.
<brentn at freeshell.org>

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