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Interesting article but left me wondering why they don't use ¹H₂¹⁶O as the "standard water"? Surely you can make that (relatively) easily in a centrifuge by sp
by rwmj 3mo ago
Interesting article but left me wondering why they don't use ¹H₂¹⁶O as the "standard water"? Surely you can make that (relatively) easily in a centrifuge by spinning out the lightest fraction of water.
- thayne 3mo agoAt the very least that has the advantage that it's possible to make more of it, so you aren't dependent on a limited sample of standard water.
- ameliaquining 3mo agoThe article doesn't mention this, but they actually did make more. Or rather, they put together a new sample, VSMOW2, in 1999. It's exactly the same as VSMOW, to within measurement error. Like the original, you can buy it from the USGS. Documentation (including how it was prepared): https://nucleus.iaea.org/sites/AnalyticalReferenceMaterials/Shared%20Documents/ReferenceMaterials/StableIsotopes/VSMOW2/certificate%20%20VSMOW2%20SLAP2%20052026.pdf https://nucleus.iaea.org/sites/AnalyticalReferenceMaterials/... This actually goes both ways; VSMOW itself was carefully made (by mixing in small amounts of water from other sources) to match the composition of an earlier reference water sample, NBS-1, which came from the Potomac River (one supposes it was a convenience sample). NBS-1 is no longer used as a point of reference, since everyone's agreed to use VSMOW instead, but the USGS sells it too.
- cozzyd 3mo agoJust wait for the new reflecting pool standard of official water.
- barbegal 3mo ago18 O enriched water is available to buy but the pricing suggests it's quite expensive to separate 16 O from 18 O. And you get much less variability in the ratio of isotopes from mixing compared to separating a single isotope as much as possible.
- 0cf8612b2e1e 3mo agoI at first thought you meant taking hydrogen gas and burning it in O18, which seems even simpler than bulk processing water.
- bell-cot 3mo agoNot an expert, but... The use case for this water is calibrating ultra-precision instruments. The use case for those instruments is measuring water with normal-ish isotope ratios. Calibrating your ultra-precision instruments to a point far away from their normal use case is asking for trouble.