Hi there Mike, Yes, I considered after syringing several times on the very first day that, 1) On observing the meniscus of the liquid I realised it would be pretty difficult to determine that I have *exactly* 5cc's in the syringe, and repeat that *every* time I syringed, 2) How accurate the scale *actually* would be in this small range, 3) What variations could come into play with varying temperatures of water etc, and then to clinch it, 4) speaking to Tom, Marshall and Frank about it was the deciding factor. As you say though, it was still a worthwhile thing to do for me as no matter how naive my idea was it *did* teach me the "orders of magnitude", and made me realise that this proved to be of little value in the scheme of things. Like I said earlier, it was an idea in principle, just didn't work in practice, but if one never never goes one never never knows. Far better to pick someone else's brain I spose, much easier, but then there's no challenge is there, and the lesson is not as well learnt as in doing it for oneself? That's the downside of not being an academic I guess...damn it, nevermind, that's what you people are for right? To bring us back on the straight and narrow if/when we stray too far <g>. Cheers
N. > From: [email protected] > To: [email protected] > Date: Wed, 2 Mar 2011 17:35:23 -0500 > Subject: RE: CS>Wet weight? > > Dear Neville, > > As Marshall has noted, one of your sources of error would be the > syringe... It is unlikely you can measure the 5 cc's of water > repeatedly to within the accuracy of the scale, let alone measure the > addition of a few micrograms of silver on a balance that is accurate > only to milligrams. > > A good exercise would be to just measure out 5 cc's of distilled water > five different times and see how much variation you get within just > that operation alone. > > If you're talking 10ppm CS, that's 10 milligrams of silver in a liter, > or 50 micrograms per 5 cc's. So, the difference in mass between 5 grams > of water and 5 grams of water PLUS 50 micrograms of silver would > probably be WAY less than your errors in measuring out the water, > totally apart from the resolution of the scale, which wouldn't be able > to even see the silver weight. > > It's a worthwhile experiment, and can teach a lot about orders of > magnitude, and the precision and accuracy of measurments. These are > essential to all science. > > Peace, > > Mike D. >
