News for the day: mg/L <> ppm

[Silver_Is_Money]

We have all been somewhat lied to when we are so often told in the brewing world that mg/L and ppm are the same.

mg/L is a weight to volume relationship

ppm is a weight to weight relationship

Therefore the only possible time when they can actually be one and the same is when liquid weight and volume are precisely one and the same as to unit value.

DI water at 4 degrees C. is essentially 1.000 gram weight per 1.000 mL volume, so for specifically the case of highly pure DI water at 4 degrees C. one can effectively claim that ppm and mg/L are the same.

But the density of beer is never 1.000 gram per 1.000 mL at 4 degrees C. And on top of that, the density of 1L of DI water with 1 gram of CaSO4 added and dissolved is not 1.000... grams per 1.000... mL.

Just saying....

And for bonus points to ponder in wonderment whereby to introduce yet more confusion, density does not equal specific gravity....

 

[Big Monk]

So what’s the practical application/improvement based on this?

That’s what people are going to be interested and want to know.

 

[Silver_Is_Money]

I came across this dilemma when attempting to formulate an acid blend along the lines of CRS.

If it is formulated such that (for example) the Cl- ion is 64.88 mg/L, and (as per some literature) this acid blends specific gravity is 1.085 (whereby its density is ~1.08175), then:

64.88 mgL/~1.08175 = ~59.98 ppm

64.88 mg/L <> ~59.98 ppm

 

[Silver_Is_Money]

The most logical solution to the problem appears to me to be one where everyone goes strictly by mg/L and abandons ppm.

 

[Silver_Is_Money]

The most logical solution to the problem appears to me to be one where everyone goes strictly by mg/L and abandons ppm.

I guess that a case could be made whereby we effectively do exactly the above, and we incorrectly thereby conflate ppm and mg/L into the exact same thing, with that thing being mg/L. This is fine as long as mg/L underlies the foundation of said self (as well as collective) deception/delusion, and ppm is not the foundation.

 

[IceChisel]

Should you inform the water calculator creators? They could then correct their software.

 

[Silver_Is_Money]

Should you inform the water calculator creators? They could then correct their software.

I presume they simply use mg/L and call it ppm (albeit on a technical level, incorrectly). That's what mine does at least.

 

[IceChisel]

I was being sarcastic. What is the average error in reported ppm for something like Cl or SO4? If the calculator is saying 100ppm and really it's 50ppm or 150 ppm then that's probably something to correct. Most have probably adapted to what their software is telling them even though it's incorrect, kind of like IBU formulas.

 

[Brooothru]

I presume they simply use mg/L and call it ppm (albeit on a technical level, incorrectly). That's what mine does at least.

The phenomenon you point out is technically true. The rubric under which we operated in the Navy to describe this fact was, "Close enough for government work."

Or as I prefer to observe its empirical significance (as pertains to home brewing):

"Measure with a micrometer, mark with a grease pencil, cut with an axe, fit with a sledge hammer."

 

[Silver_Is_Money]

I was being sarcastic. What is the average error in reported ppm for something like Cl or SO4? If the calculator is saying 100ppm and really it's 50ppm or 150 ppm then that's probably something to correct. Most have probably adapted to what their software is telling them even though it's incorrect, kind of like IBU formulas.

For Cl- sourced from CaCl2 the error can be huge, but it is due to the end user generally not at all knowing the actual hydration state of their supply of CaCl2. The rest of the mineral valuations should presumably be right close, albeit there is always a purity issue, and the software generally presumes pure whereas in the real world nothing is likely pure unless you pay an arm and a leg for it. Rounding errors in molecular weight presumption are an admitted source of differences between calculators, but these are small enough to be (as the above poster stated) more than close enough for government work. Since none of us know the mineral content(s) of our malts to begin with, and they are indeed substantial, as well as being substantial in their ability to vary (due perhaps in big part to soil based mineral conditions, fertilizer based mineral conditions, and watering based mineral conditions), all of this is likely a moot point anyway.

 

[3 Dawg Night]

"Measure with a micrometer, mark with a grease pencil, cut with an axe, fit with a sledge hammer."

Beat to fit, paint to match.

 

[Big Monk]

Isn’t this really just an issue of semantics? Aren’t we all calculating mg/l WRT brewing minerals and just calling it ppm as a convention?

Every background calc I do for minerals is done as mg/l.

 

[Silver_Is_Money]

Isn’t this really just an issue of semantics? Aren’t we all calculating mg/l WRT brewing minerals and just calling it ppm as a convention?

Every background calc I do for minerals is done as mg/l.

Yes, in a way. But we all must do our part to see it and process it as mg/L. Processing it as true ppm would be nigh on impossible.

 

[Big Monk]

Yes, in a way. But we all must do our part to see it and process it as mg/L. Processing it as true ppm would be nigh on impossible.

So what's the issue then? I only ask because you have been banging this drum for some time and it seems to boil down to a semantic issue. Unless i'm missing something deeper.

I think your beef is really the reporting of profiles in ppm, correct?

 

[Silver_Is_Money]

So what's the issue then? I only ask because you have been banging this drum for some time and it seems to boil down to a semantic issue. Unless i'm missing something deeper.

I think your beef is really the reporting of profiles in ppm, correct?

I just wanted to inform those likely to be unaware that ppm and mg/L are not the same thing. And sometimes they are extremely not even remotely close to being the same thing. That's all.

And yes, to fully clear the air we should abandon ppm's. But first the sell/explanation must go out as to why. And we must then hear and gauge the receptivity of the response.

 

[Silver_Is_Money]

So what's the issue then? I only ask because you have been banging this drum for some time and it seems to boil down to a semantic issue. Unless i'm missing something deeper.

The drum I've actually banged for some time is one whereby "strict" adherence to mg/L's (or ppm's) with respect to "water profiles" fails to provide sufficient information and mEq's/L pass the "water profile" related tests that mg/L fail. ppm vs. mg/L is something different altogether.

 

[Big Monk]

The drum I've actually banged for some time is one whereby "strict" adherence to mg/L's (or ppm's) with respect to "water profiles" fails to provide sufficient information and mEq's/L pass the "water profile" related tests that mg/L fail. ppm vs. mg/L is something different altogether.

Gotcha. Pardon my comment then, as I neglected to make that distinction. I don’t think the ppm vs mg/l thing is a big deal, or even a deal at all, but you know I wholeheartedly agree about the difference between source mEq and added mEq and it’s effect on pH.

 

[Brewbuzzard]

I got it, let's invent a ppm meter. See how easy life can be. Bazinga!

All kidding aside every detail matters in the pursuit of excellent beer.

 

[Silver_Is_Money]

In a world where all marbles are of the same weight, a single red marble stirred into to a box of 999,999 blue marbles would mean the box of marbles is 1 ppm red. But it would not very likely mean that the box of marbles is 1 mg/L red (albeit that this case is still remotely possible).

 

[mabrungard]

Larry, you are making AJ proud. Your concern over this insignificant terminology makes you as pedantic as him.

While mg/L is not the same as ppm, it’s very close for dilute aqueous solutions that we deal with.

 

[Brewbuzzard]

Larry, you are making AJ proud. Your concern over this insignificant terminology makes you as pedantic as him.

While mg/L is not the same as ppm, it’s very close for dilute aqueous solutions that we deal with.

Thank you Sir, I just learned a new word. Larry... Ouch!

 

[Silver_Is_Money]

Thank you Sir, I just learned a new word. Larry... Ouch!

Yes, the wording was indeed harsh and painful as intended. And in the study of philosophy it even has a name. It is called the "Argument From Intimidation". It is meant to totally disarm and destroy the opponents position (mainly in the eyes of others, not necessarily or even likely in those of the opponent) by substituting moral judgment for intellectual argument. But I granted a 'like' for the addition of line 2, and in the spirit of brewing comradery and peace. Line 2 was in reality all that was needed to be said.