most needs for such water are for calibration of instruments - many labs run stable isotopes measurements which has many applications from tracing how plants use water to measuring your metabolic base rate .. so the main use case it to calibrate instruments because it's really difficult to have an absolute measurement of stable isotope ratios from first principles - and the ratios are so small you typically express them in relation to standards like VSMOW
For more context, sample reference materials from the NIST reference catalogue are not meant to be exceptionally high purity examples of the sample -- SRMs are usually commercially-produced products. The real value is that each sample comes with a datasheet with incredibly detailed and accurate measurements that are (as you said) used for calibration of measuring devices in industrial settings. To quote a Veritasium video about the topic from a few years ago[1], "the thing you're paying for is not the peanut butter, it's the knowledge of exactly what is in the peanut butter".
Truth. I once paid nearly $500 for a set of 17 certified, calibrated wooden pencils, with documentation showing that each one met their rated hardness levels of 9H thru 6B. And for $500, they don't even come with erasers, that is an added-cost option.
I'd like to ask a more specific question than my sibling's excellent "Wait, why?" question :)
Why offer erasers on these things? The procedure described below has nothing to do with using these as pencils, and at $500 for a pack I can't imagine anyone, anywhere casually drawing with these.
(Is there another procedure, similar to the one described below, except instead of dragging the pencil tip across a surface you drag the eraser across it? )
His link includes procedures, which suggest he was testing the hardness of some surface coating or similar:
> For the pencil hardness test, reference ASTM D3363, pencils of increasing hardness values are moved over the surface in a precisely defined way until one lead damages the surface. Surface Hardness is defined by the hardest pencil grade which just fails to damage the surface.
> Observe the pencil track. Sufficient pressure must have been applied either to cut or damage the coating or to crush the lead pencil point.
> If neither coating damage or pencil point crushing is observed, repeat the test until a definite observation is made.
> If scratching or damage of the surface occurs, proceed with the next softer pencil grade and repeat the testing process until a pencil lead grade is found which crushes and does not damage the coating.
> If crushing of the hardest lead should occur, the coating is therefore extremely hard and is beyond the measuring range of this test
The pencil hardness scale is commonly used to assess paint film hardness by checking what is the softest pencil that can mar the surface when you scratch it with a given force. In this case, we needed to assess whether exposure to a certain chemical degraded the integrity of the paint coating that we were counting on for corrosion protection.
You use the kit to test the harness of a finish coating, like a paint or a ceramic coating for cars. Pencils have their own hardness scale which can be used to gauge the hardness of the coating. Its really more of a relative qualitative test than quantitative as you'd use this for sample/coupon testing identical coatings. There are more absolute, quantitative methods to measure various hardness characteristics (scratch, indentation, and rebound). Like you'd use the pencil kit on a factory floor to make sure each paint sample performs the same, the sample being a small area on the product or a plate that's painted the same way.
That’s $508 for two cartons for 400 cigarettes total, so $1.27 per cigarette. They’re not characterized like the peanut butter, they’re just manufactured to a specific QC standard.
California/New York prices are easily $0.75/cigg so it’s not that much more expensive.
I had seen the cigarette. But but not the meat which costs $2,690 for four tuna-can size cans and is a mix of pork and chicken
Thinking of a concept for a restaurant meal along the lines of a calibrated fried spam dinner, that costs ~2k for about a can worth, fried like they do in Hawaii.
Come to think of it, would love to see an “iron chef- calibrated foods” edition.
Yes, it’s a bit frightening to know what a hidden dependency NIST is on many things. In my industry, all calibrations ultimately derive from physical NIST standards for resistance, frequency, etc.
I suspect the fear comes from both seeing NIST as a single point of critical failure, and perhaps also that it is a far less resilient and/or far more vulnerable, institution than may have been previously realized.
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.
The 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/...
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.
18 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.
Unless you're actually measuring something with any importance, a gallon is about 4 liters. More closely 3.78541... But saying a quart and a liter are about equal is often good enough.
You can centrifuge it. Heavier molecules move closer to the bottom. Repeat until you reach the desired purity.
You need shitloads of ordinary water to extract a liter of heavy water. And I'd be surprised if there's any superheavy water in that, because tritium radioactively decays.
Fun fact: Heavy water is slightly toxic to humans. If you only drank heavy water, you'd die as it shifts the chemical reactions in your body out of balance. A moderate amount is fine though.
Emphasis on the slightly. I believe it would take weeks of only consuming heavy water. You could certainly drink a single glass of it without ill effects.
IIR, a number of rich & famous people have developed severe mercury poisoning after extended conspicuous consumption of swordfish and other very expensive/very contaminated seafood.
Obviously the luxury bottled water industry is missing out on the potential of D2O and T2O.
This is why we should ditch Celsius for Kelvin. I never liked how we coupled 0 and 100 to where water freezes and boils under certain conditions. Kelvin doesn't rely on non-invariant reference points.
Why would five-digit years have become popular? They seem roundly a bad idea.
Years aren’t even four digits by custom: they’re just numbers, with the present idiosyncrasy of eschewing a grouping (thousands) separator. We say the sack of Rome was in 410, not 0410. Only for specific serialisation purposes have we ever recorded fixed-width dates, acknowledging that there are limits to this. The recording of two-digit or offset-by-1900 years in computer systems was a case of bad judgement. The recording of four-digit years as is presently customary is pragmatic and entirely adequate for the next few thousand years, and there’s no point in designing things beyond that horizon.
this is actually why i like fahrenheit the most... 0F is "really cold" and 100F is "really hot", whereas in celsius 0C is "kind of cold" and 100C is "uninhabitable". it makes sense for the 0-100 range to be reserved for temperatures frequently encountered in our habitat as humans i think...
That’s a biased view that leads to a scale only convenient for people living in particular latitudes. Now talk to someone living near the equator like Singapore, and 0F is unimaginably cold (even 40F is basically unheard of), and 100F is very hot but not extraordinarily so. Then you talk to someone living close to the arctic and the converse is true.
All this talk about 0F to 100F being frequently encountered probably reveals your local climate conditions more than it helps define a useful global standard for all humans. We should accept that humans live in more diverse conditions than we intuit and such a scale probably won’t be useful for all.
> Now talk to someone living near the equator like Singapore, and 0F is unimaginably cold (even 40F is basically unheard of), and 100F is very hot but not extraordinarily so.
Bad example--Singapore has never had a single 100F day in recorded history. The highest temperature ever recorded was 37C/98.6F. As a small island its climate is greatly moderated by the masses of water around it. It rarely gets above 90F.
The broader point about the 0-100 Fahrenheit scale being convenient for people from a certain climate is correct, of course.
Now I'm imagining some kind of timezone-like temperature unit that varies around the world, and a "100 things programmers should know about ___" post about all the intricacies and special cases.
Ooh, and it could shift seasonally so that summer temperatures and winter temperatures can both be in the convenient range. And every locality could shift a different amount and at different times of year according to their local climate.
Next, we can look into reforming those pesky mass and volume units…
Where I live now (Hyderabad, India), the record low is about 45°F, the temperature will not drop below 50°F more than two or three days in a year, and the daily maximum will not drop below 100°F for at least fifty consecutive days in the summer.
> That’s a biased view that leads to a scale only convenient for people living in particular latitudes
I mean, the other option is cool vs dead
> We should accept that humans live in more diverse conditions
The second most diverse range of temps in the world is smack dab in the middle of the US: South Dakota up through northern Minnesota. Most years that area experiences -40F in the winter and 110F in the summer.
Celsius maps nicely to the temperatures observed in a typical Finnish sauna. 100C is among the highest typical sauna temperatures (very relaxing in dry air), and afterwards you cool off with water around 0C
Also, having 100C as water temp for black tee and 80 for green tee is nice to remember
This has always been my primary argument in favor of Fahrenheit. It makes sense for humans, which is all a majority of the population really cares about. In addition, it's more granular. Sometimes turning the thermostat up or down by 1C could be too much, where 1F is just right.
In science and math, I can see where having round numbers for commonly used temperatures would be useful, but if 0C and 100C are the only places that happens, it's not that hard to memorize 2 numbers.
You only think it makes sense for humans because it makes sense for you, where you live the same way you feel changing a thermostat by 1F is perfect but 1C is too much: that’s true for you, not universally.
Fahrenheit functionally requires you to be biased in order for it to seem like a good system.
It provides greater granularity in the range of human comfort, without descending into decimals. How is that not more useful for day-to-day human usage?
0F is cold, 100F is hot. I experience both of these temperatures outside where I live every year.
-20C to 40C seems much more arbitrary as a way to measure the zone humans mostly live in.
I would wager that the outdoor and room temperature are an overwhelming majority of human use for temperature. It seems like it would make sense to optimize for how temperature is more commonly used at a population level.
I would say those who see Celsius as a good system are also biased, because they grew up with it and it’s what they’re used to.
> 0F is cold, 100F is hot. I experience both of these temperatures outside where I live every year.
This is just your location, and things like this vary around the world a lot. Hell, they vary in the US. To me, where I live (in the US), 0F and 100F aren't really useful as benchmarks; we don't see either of those temperatures here, ever. The normal range is more like 40F-80F (with extremes maybe down to 25F and up to 90F, but those numbers push credibility a bit).
But ok let's look at averages. Do "most humans" (whatever that means) really live within 0F to 100F? That doesn't really pass the smell test for me; there are lots of humans who live in places where it regularly exceeds 100F. And in those places I doubt it gets anywhere near 0F, with many places never getting down to even 20F. There are also lots of places that get warm, but will never see 100F, and seldom see 90F.
It's all super super arbitrary.
Having said that, I still prefer F over C, but I don't pretend there's any rational reason for it: it's just because I grew up with Fahrenheit, and no matter how hard I try, I just can't feel Celsius the same way. I feel like you maybe don't interact with too many people who grew up with Celsius; you'd probably realize they feel the same way about C as you do about F, and that there's no rational reason for it. It's just what you were trained to think and feel in, and it stuck.
The -40C was a typo, should have been 40C, to mirror the 0F to 100F, rounding a bit to make it less silly. It’s been fixed now.
Millions do experience 0F, and it’s ok to not use the full range. At or around 0F is cold, as you move closer or beyond it, it’s cold. As you move closer to or beyond 100F, it’s hot. Most people would likely prefer to never deal with <0F or >100F.
Millions -- hundreds of millions, even -- regularly experience -10F and 110F as well, but you've arbitrarily picked 0F-100F, so I guess their experience doesn't matter, because you prefer round numbers?
> you feel changing a thermostat by 1F is perfect but 1C is too much: that’s true for you, not universally.
I've noticed that here in Japan all the AC units seem to be adjusted by half a degree Celsius at a time, so I do think 1C is a bit much even for people who never used fahrenheit.
Living in Australia and India, I have never encountered such a thermostat. But I do vaguely recall encountering a thermostat somewhere at some point that went up by twos in Fahrenheit.
I would guess you would only encounter ½°C steps on units that support both Celsius and Fahrenheit, so that they’re closer to parity. I don’t think any unit that I’ve owned has supported Fahrenheit at all.
Celcius is pretty intuitive actually. It takes atmospheric pressure into account, Water is pretty abundant on the surface of the planet, and life kinda depends on it. It's a remarkable substance and quite stable. I dont think theres another substance where we can see all three phases with kitchen appliances and still consume it. Equally good for bathing and drinking. I need steam to clean clothes and cook my food. Using water as a benchmark for how we measure temperature is remarkably useful.
With all of those examples, the actual temperature doesn’t really matter.
For drinking and bathing, people go by feel. In the kitchen, the freezer makes water freeze, and the stovetop will make it boil into steam, but exact temperatures aren’t really relevant here either. The same goes for ironing clothes, the iron just does it.
When I think about where explicit temperatures are needed in the home, the oven and thermostat are the two things that come to mind. Water is pretty irrelevant for both of those. For cooking or frying someone may monitor meat or oil temps, but those aren’t water. A hot tub might have an actual temp on it, but those tend to be around 100F, not 100C, as they are meant for humans, not boiling.
Water is an amazing liquid, but I still struggle to see how measuring all our temperatures based on it makes sense.
Yes, and people who grew up with Celsius feel in Celsius, and people who grew up with Fahrenheit (like myself) feel in Fahrenheit.
Stop trying to make some sort of determination of what's logical or reasonable here. Neither one is more or less logical than the other for day-to-day layperson use; anyone can "feel best" in any scale if they were taught it at a young age and used solely that scale for the formative years of their lives. Hell, I bet you could make a kid feel in Kelvin if that's all they were exposed to for their childhood. Or in some made-up scale that takes your 0F-100F and compresses it inside 22-35.
> When I think about where explicit temperatures are needed in the home, the oven and thermostat are the two things that come to mind.
But in that case in what way is for example baking a frozen pizza from the store at 400 to 425 degrees F more relatable/convenient/natural than 200 to 220 degrees C?
It's not. When it comes to an oven, F and C are equally arbitrary, so it really doesn't matter. Optimize for what people use most, and let the other random uses fall as they may.
You have it backward. There's no absolute truth on what's optimal for what people use most. What's optimal is just what you were reinforcement-trained to feel when you were growing up as a child. That's it.
My wife says "30C" and knows exactly how that feels, while I struggle to find a reference point. I say "86F" and know exactly how that feels. Even though she prefers C, she can feel F slightly better than I feel C, as she moved to the US when she was in her teens. (Whereas I've spent my entire life in the US, outside of business and holiday travel.)
Aren’t you just remembering specific numbers though? Unless you’re trying to boil water unseen so that you can only see a thermometer, the specific 100°C mark isn't that useful.
> Aren’t you just remembering specific numbers though?
That's the thing about this. It's so tiring for people to argue which temperature scale is "better". Nothing is better or worse. What's "better" is individual, and is just "what you grew up with". Because right, you're just remembering specific numbers, and remembering how those temperatures feel. (Or in the case of cooking, remembering what those temperatures do to your food.)
> Unless you’re trying to boil water unseen so that you can only see a thermometer, the specific 100°C mark isn't that useful.
Even then it's not that useful, as water doesn't really boil the way most people think it does. (And god forbid you aren't at sea level and aren't at standard temperature and pressure.)
The temperature water boils at is irrelevant when you can just look at it to see if it’s boiling. Any stove will get it hot enough, assuming you have enough energy.
Also if you set something to heat water until it's exactly 100C/212F, it probably won't be boiling when it gets there. Some bits of it might be bubbling, but it won't be what we normally think of as "boiling".
OF will still kill you faster than 100F, and most folks aren't comfortable at 50F.
It inspires the following idea: A nonlinear scale where ~72F is 0, and +X represents the same level of heat discomfort as -X represents cold discomfort.
I actually came around to Fahrenheit for the exact same reason. 0°F and 100°F are kind of the top and bottom of the temperature range I’m going to be experiencing and anything outside that is waaay too hot or cold. In Celsius a large portion of people have to flip to negative numbers regularly during the normal year, and everything between 45°C and 100°C is completely unused.
I dunno, temperature doesn't really work like that. As a sibling mentioned, saunas: I can sit in a 190F dry sauna for about a half hour at a time and it feels hot but nice and soothing. But I can only handle a 120F steam room for maybe 10 minutes before I need to get out of there. (Speaking of the dry sauna, if someone pours a bit of water on the stones, it near-instantly feels significantly hotter, even though the temperature hasn't changed.)
Put another way, I can sit in a 190F sauna for a half hour, but a half hour out in the sun in, say, Singapore, feels awful to me. 85F where I live now (unusual but happens), in a relatively dry climate, is bearable, while the same temperature where I grew up, in a much more humid place (where it was more common), feels gross and saps my energy.
And I can be out snowboarding in 25F weather that's calm and sunny, and feel fine in a medium-weight clothing. But add clouds and wind, at the same temperature, and it's unbearable.
And to me, based on the temperatures I usually see, 15F is waaay too cold, and 90F is waaay too hot. Sure, I guess I could round that down to 100F and up to 100F, but that just feels like being arbitrary for the sake of easy numbers.
> 0°F and 100°F are kind of the top and bottom of the temperature range I’m going to be experiencing and anything outside that is waaay too hot or cold.
Food, saunas, the weather, a fever, and much more are often over 100F.
Except 0F being “really cold” and 100F being “really hot” is a personal bias of yours based on where you’ve lived. It’s not true for everyone or everywhere.
And even if it were true, it still wouldn’t work. 100F in a dry environment is nice while, in a humid environment, 100F is awful. Same for 0F, a dry and static 0F is fine while a wet and windy 0F is killer.
Experience 0F wind in central North America or Central Asia vs 0F wind on the coast and tell me it’s not different. Also, it’s killer, not a killer, as in it sucks a lot.
There's nothing stopping the use of decimal points for Celsius. Though there's also nothing stopping decimal points in Fahrenheit, the rare instance where an imperial sub-unit doesn't make things go fucky.
I think that both the Celsius and Fahrenheit scales are now defined in terms of Kelvin and a formula. Most if not all of the units of measure are no longer related to their history except for an agreement to make the new units match the old ones at some point.
You can thank Carl Edvard Johansson[1] for that, the inventor of the gage block.[2]
He was the one who decided to make it a convenient value, according to Wikipedia[3]
As a result of the definitions above, the U.S. inch was effectively defined as 25.4000508 mm (with a reference temperature of 68 degrees Fahrenheit) and the UK inch at 25.399977 mm (with a reference temperature of 62 degrees Fahrenheit). When Carl Edvard Johansson started manufacturing gauge blocks in inch sizes in 1912, Johansson's compromise was to manufacture gauge blocks with a nominal size of 25.4mm, with a reference temperature of 20 degrees Celsius, accurate to within a few parts per million of both official definitions. Because Johansson's blocks were so popular, his blocks became the de facto standard for manufacturers internationally, with other manufacturers of gauge blocks following Johansson's definition by producing blocks designed to be equivalent to his.
This makes it relatively easy to handle making metric threads on imperial machines, and vice versa, because you can use 50 / 127 gear tooth pairs to do the ratios.
An odd little factoid: A metalworking lathe will usually have a mechanism for cutting screw threads, with a multi-ratio gearbox for linking the rotation of the spindle to the motion of the carriage. For cutting metric threads, you have to change a pair of gears. So there will be a pair of gears with 50 and 127 teeth, which produces the 2.54 ratio. Then you have to look up the correct gearbox settings for each metric thread pitch in the manual. [0]
It's a big royal pain in the arse, and I've never had a machinist agree to turn metric threads on a lathe. They would rather wait a day and order a metric tap or die. Nowadays the CNC lathes just do it auto-magically.
Also, among old bicycles, there are some weird national thread standards that had metric diameters but inch thread pitches, because of machinery imported into countries like Italy and France during reconstruction after WWII.
[0] Edit: Just noticed duplicate comment preceding mine.
Sure technically yes, but also celsius is now technically defined as just Kelvin plus 273.15. Degrees have technically been redefined as exactly 1.380649×10^−23 joules
most tv makers and electronics stores in europe give you the screen size in inches first and cm second. they only come in a few common sizes so the specific units dont really matter.
Speaking of tires, its actually a crazy mixture of units here in the US. You might have a size like P215/65R15 which translates to a radial passenger tire of a 15" rim, 215mm wide tread (sidewall to sidewall), and an aspect ratio of 65 which is a ratio of the sidewall to tread width.
So a tire size is expressed in inches, millimeters, and ratios.
Yeah, but people find it perfectly intuitive that things like xenon are expensive because the material itself is rare; that kind of scarcity is a thing humans have dealt with since the Stone Age. Whereas this stuff is just water.
Depending on what state you live in, that's not bad these days.
https://shop.nist.gov/ccrz__ProductDetails?sku=1196a&cclcl=e...
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