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Week of 10 December 2007


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Monday, 10 December 2007
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08:59 - I spent some time this weekend working on the chem lab book, but I also devoted some time to expanding the outline for the home forensics lab book. I added one lab session on using presumptive tests for alkaloids. One of the tests uses a solution of potassium iodide and bismuth nitrate in acetic acid, called Dragendorff Reagent. How cool is that?

One of the neat things about forensic chemistry is that most of the "wet chemistry" tests originated in the 19th century and are therefore pretty easy to reproduce in a home lab. And, despite the proliferation of expensive instrumental methodologies like gas chromatography, atomic absorption spectrophotometry, and neutron-activation analysis, wet chemistry methods are still important, not least for presumptive tests.

Many of these instruments are extremely expensive and in short supply. The flood of requests for forensics tests means that only a tiny percentage of them can be completed with the expensive instruments, so presumptive tests are important as initial screening tests. If presumptive tests turn out negative, there's no point to doing the expensive, time-consuming instrumental tests.

And presumptive tests can be pretty reliable, although it's often necessary to use two or more presumptive tests to increase certainty. For example, a sample that is suspected to be an illegal drug might be tested with presumptive test A, which yields a specific color change if the suspected drug is present. If the color of the test solution changes appropriately, the investigator has a reasonable suspicion that that drug is present in the sample. But it's not guaranteed, because nearly all presumptive tests are subject to false positives, which occur when a completely different (and probably legal) substance causes the same color change.

So the next step is to run presumptive test B against the sample. The B test uses different chemistry than the A test, so a positive test with both A and B greatly increases the likelihood that the suspected substance is in fact present. Although the B test is also subject to false positives, the probability that a particular legal substance would cause a false positive with both tests is quite small. If there's any doubt after running A and B, the technician can run presumptive test C for confirmation.

Only when the technician is satisfied that the substance is almost certainly the suspected illegal drug is the sample sent to the forensics laboratory for confirmatory testing with the expensive equipment. That expensive equipment has one other advantage. Presumptive tests are, almost exclusively, qualitative or at best semi-quantitative rather than quantitative. Presumptive tests may tell you that a suspect drug or poison is likely to be present in a sample, but they can't tell you how much is present, at least not with a high degree of accuracy. Because quantities are important evidence in drug trials, the results of the instrumental methods are invariably used in the actual trials.

Wet chemistry methods are also important for gathering evidence in the field. Things like testing for blood traces with luminol or fluorescein, revealing latent fingerprints with ninhydrin, iodine fuming, SPR (small particle reagent, AKA molybdenum disulfide), silver nitrate, or super glue, and so on. And some of the wet chemistry methods that are doable in a home lab are quite sophisticated, for example using electrophoresis to separate DNA samples.

This is going to be a dynamite book. I just hope O'Reilly will go for it. If not, I may publish it myself.


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Tuesday, 11 December 2007
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08:46 - I just got back a whole bunch of home chem lab chapters from my editor, so guess what I'll be doing all day today.



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Wednesday, 12 December 2007
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08:25 - I blasted through final edits on eight chapters yesterday. Today, I'll incorporate the final edits on chapter 20, Quantitative Analysis, and chapter 21, Synthesis of Useful Compounds. I haven't gotten my editor's final comments on Chapter 22, Forensic Chemistry, but I'll get those done as soon as he sends them to me.

After I complete the edits, I'll be spending several days in the lab, doing setups and shooting images. I think I'll move a PC down there temporarily. It'll take up a lot of bench space, but it'll save a ton of running up and down the stairs. I need to have the text of the chapters readily available while I'm doing the setups and shooting the images, and it'll be useful to be able to edit the text immediately while I'm shooting the images. Or I may just carry my notebook downstairs.

Mary and Paul are coming over this weekend for dinner and to do a lab inspection. I doubt it'll ever happen, but if the feds do kick down my door one day and bust me for unauthorized possession of a chemistry lab, it'll be useful to have two independent expert witnesses who can testify that my lab is for the purpose of writing science books rather than making illegal drugs or explosives.



11:37 - I finished up the edits on all of the chapters I have, so it's time to get the lab cleaned up a bit and set up to shoot a whole bunch of images. I decided to carry my antique Compaq Armada E350 notebook down to the lab so that I could read along in the text as I set up images to shoot. That notebook has only a Pentium III/750 processor and, IIRC, 512 MB of RAM. It has Xandros installed, so I'll need to do something about that. (Since Xandros signed a patent pact with Microsoft, I've refused to have anything to do with Xandros.)

I thought about installing a low-footprint Linux distro on the notebook, but instead I decided to give Linux Mint a try. I'm downloading it now from a torrent, so we'll see how it works. The torrent is unusually fast. It's running about 600 KB/s sustained, which is about the limit of my broadband connection.


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Thursday, 13 December 2007
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11:13 - I got chapter 22, Forensic Chemistry, back from my editor last night and finished the updates on it this morning. Today is a lab day.

As it turned out, I wasn't able to load Linux Mint or Ubuntu 7.10 on my antique notebook. Not surprising, considering the thing has only 256 MB of memory rather than the 512 MB I thought it had. I also found out that the notebook currently dual-boots an old version of Xandros and Windows 2000, so I'll probably just leave it as is for the time being. It's good enough for what I need to do in the lab. It has an 802.11g Wi-Fi card in it and one USB port, which is all I really need for connectivity.



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Friday, 14 December 2007
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08:38 - Here's a politically-incorrect article I was surprised to see, even on FoxNews.com: Dogs Save Australia Boy, 2, From Drowning

The two canine heroes pulled a drowning 2-year-old boy from a dam pond and dragged him up the bank to safety. One of the dogs was a Rottweiler mix and the other a Staffordshire terrier (one of the breeds commonly called pit bulls), two of the breeds most feared by people who don't know any better.

In reality, of course, pit bulls are one of the breeds least likely to attack humans, having had aggressiveness toward humans bred out of them for many generations. Pit bulls were originally bred not for dog fighting, but for bull- and bear-baiting. The dogs were often badly injured in the pit, and the safety of their handlers depended on the dogs being completely unaggressive toward people under all circumstances, including when the dogs were badly injured. Anyone who has experience with pit bulls (other than puppy-mill dogs, which are dangerous regardless of the breed) knows that pit bulls are playful, gentle, and affectionate pets.



I spent yesterday afternoon in the lab, getting things cleaned up and organized a bit. More of the same today. I need to reserve some counter space temporarily for doing setups and shooting images.

And I found out why the notebook computer wouldn't load Linux Mint 4.0 or Ubuntu 7.10. It has not the 512 MB of RAM I thought it had, nor even 256 MB, but only 128 MB. Crucial no longer has this model listed on its configurator, but I see that a pair of 256 MB SDRAM PC133 SODIMMs for a similar model costs over $100. No, thanks. I'll just retire this system to the lab long enough to get done what I need to get done. Then it goes back in astronomy kit for use as a field notebook, for which it's perfectly adequate.


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Saturday, 15 December 2007
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Sunday, 16 December 2007
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