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Comment by TeMPOraL | Hacker News Reader

On a related note, I've been dealing with some process chemistry recently, and I've noticed that a lot of dimensionless quantities that are ratios retain their original units - I've seen many cases of units like e.g. [kg/kg]. Not sure what's the reasoning behind this, but I suppose this prevents mixing up [kg/kg] with [m/m] and other unrelated ratios.

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It's useful to distinguish between mass ratios versus volume ratios. Some materials can vary in density depending on how they're packed or compressed.

If it's something like milligrams of X per gram of Y I think it's generally better to just write it like (mg X)/(g Y)

Or, in electrical engineering, "power factor" and the distinction between kVA and kW.

And in communication theory / information theory there is spectral efficiency, which is 1/s/Hz (rate over bandwidth. Sometimes given in bits, sometimes in symbols)

This commonplace in liquor stores and pharmacies: concentration by volume is v/v and by weight is w/w.

https://www.bode-science-center.com/center/hand-hygiene/hand...

If you are having snags with dimensionless ratios in chemistry, why not talk to any half competent cook/chef? They don't piss about like that!

The reason your quantities (LMT etc) are dimensionless is because you need to bake a decent cake or mix a cocktail and get a grip 8)

I am being flippant but I don't think that mixing kilos and meters in any unlikely ratio is likely to end well. They tend to become quite forceful if not mixed carefully.

Well done. Jokes and puns aren't appreciated on HN, but I see what you did there.

What were the jokes and puns?

OP was being silly, and kg m / s^2 is a measure of force, so you have to mix them carefully or they might act forcefully.

"Jokes and puns aren't appreciated on HN"

You have to pick your time(zone) when deploying them. I generally find that GMT/UTC >=+6 is when a sense of humour failure generally kicks in. At +8 it relents a bit when en_AU kicks in and is reinforced at +11 by en_NZ.

Worst downvotes I ever got, in response to a fellow from Google expressing a very uncontroversial opinion and then making it clear it was only his own opinion, I wrote: "Hi Jim, this is Chet from HR. Let's have a chat on Monday." Even my "Sorry, bad joke. I'm not 'Chet' and I don't work at 'Google HR'" response got downvotes. Many, many responses hating on Google HR in particular and HR in general.

> If you are having snags with dimensionless ratios in chemistry, why not talk to any half competent cook/chef? They don't piss about like that!

I don't! Also, doing this would go against my belief that I already mentioned on HN several times - that the difference between process chemistry and cooking is that the former actually cares about the quality of outcome ;).

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