Consensus on the notation of dilutions

[Steve Smith]

Sure, i will use + notation, even if some will use : i will consider it as +.

That's what most of us do.


Steve.

 

[tkamiya]

As long as you are consistent in your own practice, you'll be fine.

 

[Photo Engineer]

I have been surprised by the wide variety of methods used in all areas regarding dilution. I think that we must agree to disagree. But,when we post or publish something, we should write or dilution down in clear and unambiguous terms so that everyone else can understand what you have done.

PE

 

[Steve Smith]

The problem is what we individually think of as clear and unambiguous might not be to someone else.

Before this topic was raised on APUG a few years ago I thought that everyone treated 1:3 the same way as me. i.e. one part to three parts making a total of four and didn't know that anyone thought of it in a different way.

I think we should all use + rather than : As far as I can tell, that is clear and unambiguous.


Steve.

 

[H2O]

Yuckity yuck.......

It is suprising as you insist on your true. One true.
Sorry, but I regret your students that they don’t teach other ways of the solution preparations, that they won’t meet with other possibilities how to describe a composition of different mixtures (solutions).

Your consideration is based on simple dilution equation:
V(f) × c(f) = V(i) × c(i)
Where V(f) and V(i) are volumes (final and initial) for example in mL and c(f) and c(i) are concentrations (final and initial) for example in mg/L (or mol/L).

From this equation so-called dilution faktor (DF) can be derived.
DF = V(f) / V(i) = c(i) / c(f)
It says how many times the final solution is diluted against the initial solution.
Or, how many times the final solution should be diluted against the initial solution if there is such instructions for preparing the final solution from the initial solution.
DF is greater than 1 and it is expressed by one figure, not by ratio! (Usually)
The reciprocal value can be admited, but I don't like it.
OK, DF (reciprocal value) is your criterion.

But there are more possibilities how to describe composition of mixture.
For example mass fraction, often expressed in percentage, which is fraction of mass of one component to total mass of mixture. Its using is (I hope) very simple. For example water solution of some soluble salt at concentration 20 % (mass fraction = 0,20) means 20 g salt plus 80 g (mL) water.

And now I recommend you to study the following material from IUPAC:
http://pac.iupac.org/publications/pac/pdf/2008/pdf/8002x0233.pdf
It si enough to find „mass ratio“.
Do you see that it is possible to describe a composition of mixture by means of such fraction?
This fraction expresses mass of one component to mass of the second component! And the above mentioned example looks 20/80 (=0,25). It is very near to our 1:4. And just such unusual notation gives signal that is 1+4.
And mixing ratio for example 1:0,5 is 1+0,5 etc. (what is your explanation with such recipe?).
And as example I thing was stated earlier. Prepare four components mixture (solids, liquids) in mass ratio 1:0,5:4:20 (where will your explanation be?)
It is no matter if the principle of mass ratio is applied to mixing liquids in volume units.

This mass ratio is known to chemists as relative mass fraction and its application is comfortable in calculations in such technologies as are drying or adsorption. In this case it should be better use for the „normal“ or ordinary mass fraction (related to total mass) name absolute mass fraction, but it is not necessary in ordinary life.

(Two notes to your „serial_dilution“.
1.
The explanation is based on similar dilution equation as is described above:
V(f) × c(f) = V(i) × c(i) + V(s) × c(s)
(s) means solvent and in your case c(s) = 0; V(s) = 9 mL,
But!
This equation is true if V(f) = V(i) + V(s), so-called additivity of volumes is assumed.
Yes, in many many cases of water solutions is true, but this assumption MUST be stressed, especially to students during pedagogical process.
2.
It si important after additon of initial solution to mix final solution before taking a new amount. I am not sure how this mixing is important in bacterial cultivation but I am
fully sure that mixing for preparation the most chemical solutions is very very important.

Both notes (by my opinion) are missing in your serial.)

And in the end some pictures (my serial what means 1:X). It is not necessary to understand in German (even I know very pure German )

 

[Tony-S]

It is suprising as you insist on your true. One true.

No where did I say this, so please don't say I did. There are many ways to do dilution problems and I am not disputing any of the methods described here. What I, and others, are saying is that communicating to others using the ':' is ambiguous, while using the '+' is not.

 

[graywolf]

Kind of an interesting conflict. I believe in British usage they read that 1:50 as 1 in 50, or 1+49. In American usage we would actually read 1:50 as 50 to 1, or 1 + 50. As Winston Churchill said, "Two countries divided by a common language".

What surprised me is the Americans in the thread that think 1:50 means 1 + 49. They certainly weren't taught that in school, unless they had a foreign teacher who was unfamiliar with American usage.

What confuses me is why anyone in either camp would think 1:1 = "stock solution", why would you label some thing as a mixture if it was not????? I think anyone would be more likely to say, "Do Not Dilute", if it was labeled 1:1, I would think they were using the American notation for (1 + 1). And just for the hell of it I ran upstairs to check my old bottle of Rodinal, we usually say 1:50 (50 to 1) when talking about diluting it, it is labeled 1 + 50, so those Germans seem to be using the notation in the same way we Americans do. On the other hand, my fixer is labeled 1 + 9.

Please do not let this interfere with your "MY way is the WAY" debate.

 

[Photo Engineer]

So, what is unambiguous?

How about 1 part A and 1 part B to make 2 total parts. Or 1 part A and 9 parts B to make 10 total parts. You can substitute liters, ml, oz or quarts for the word parts! This is not ambiguous.

PE

 

[zsas]

Tony I bet that everyone agrees that : can be ambiguous but in the small-analog-darkroom-chemistry-mixing-community, does anyone ever (manufacturer or member here), ever list their recipes and use the : to mean the methodology you describe, used in this community? I can just as easily post here in Swahili by using a English to Swahili translator, but that is generally not the communication convention used here, see my point? I think your convention is used, just not photographically, and therefore I think you are bringing your communities convention and trying to impress it upon another community, where it is generally not used.

As I, PE, and many others reiterate, we always should be clear when we discuss chemistry, but I ask you seriously, does anyone really use : in the manner you describe in photographic circles? If the answer is yes, then I think your point is extremely valid, otherwise you are using some obscure methodology (to the photographic community) to make your point

 

[cmacd123]

And any of us who strted Photography using the Kodak Publications like "Basic Developing, printing and enlarging" learned the 1:1 is one part of developer and one part water, around the same time we were learning that "F" paper is glossy.

 

[Dismayed]

There's a reason that chemists use molarity - only the initiated understand the definition so we don't have to defend it.

 

[Tony-S]

What surprised me is the Americans in the thread that think 1:50 means 1 + 49. They certainly weren't taught that in school, unless they had a foreign teacher who was unfamiliar with American usage.

I learned it from Americans - high school, undergraduate and graduate teachers. I've never had it any other way and I was born and raised in Kansas. Maybe it's a Kansas thing?

What confuses me is why anyone in either camp would think 1:1 = "stock solution", why would you label some thing as a mixture if it was not?????

It's simply nomenclature. To me it means "undiluted" or "neat" or "straight".

So, what is unambiguous?

The use of the plus.

How about 1 part A and 1 part B to make 2 total parts. Or 1 part A and 9 parts B to make 10 total parts. You can substitute liters, ml, oz or quarts for the word parts! This is not ambiguous.

That's perfectly clear. It also has no colons in it.

Tony I bet that everyone agrees that : can be ambiguous but in the small-analog-darkroom-chemistry-mixing-community, does anyone ever (manufacturer or member here), ever list their recipes and use the : to mean the methodology you describe, used in this community? ...but I ask you seriously, does anyone really use : in the manner you describe in photographic circles? If the answer is yes, then I think your point is extremely valid, otherwise you are using some obscure methodology (to the photographic community) to make your point

There are four people in the first 14 posts who hold this same view; that is, the colon can be confusing while the plus is not.

There's a reason that chemists use molarity - only the initiated understand the definition so we don't have to defend it.

I'm not sure why you're mentioning molarity. I've never seen it used with photographic chemicals. Have you purchased photochemistry that says to make a molar solution? If so, what was it?

 

[MattKing]

I was going to post something here about a colonoscopy, but I thought better of it.

And I continue to be entertained.

 

[zsas]

There are four people in the first 14 posts who hold this same view; that is, the colon can be confusing while the plus

I agree that it can be confusing but only think it is confusing when folks who might use : in applications in non-photographic-chemistry-mixing-scenarios get involved. I bet Kodak went with the traditional way (ie 1 part stock to 1 part water is 1:1) because they were selling consumer and B2B chemistry kits, not chemistry to be mixed by biochem folks to create pharmaceuticals, etc. My point is that folks who might work in fields outside of photography are the only confused ones because they mix alternatively when using : notation, but really ask you seriously, does any manufacturer or person here post his/her photographic recipies using the mixing schematic you use in your laboratory at work?

I have not seen it but I cd be wrong.

Regardless I agree we all need to be clear what we mean when we write mixing schemas, so it is a win-win for all sides of the debate

 

[Curt]

So have I but not everyone agrees with us!


Steve.

I use 1:2, 1:3, 1:4, etc. notation but readily understand 1+2, 1+3, 1+4, etc..

 

[Toffle]

I can just as easily post here in Swahili by using a English to Swahili translator, but that is generally not the communication convention used here, see my point?

And for fun, we could all set our clocks to Swahili time.
I'm surprised how contentious the question of dilution becomes every time it arises here. Whatever your position on the subject, I hope you are all taking the time to joyfully take and make photographs.

Cheers,
Tom

 

[Gerald C Koch]

As Winston Churchill said, "Two countries divided by a common language".

The correct quotation is "England and America are two countries separated by a common language" and it is by George Bernard Shaw. Just as Ingrid Bergman never said "Play it again, Sam." Someone should compile a book titled "Quotes That No One Ever Said."

 

[Steve Smith]

Someone should compile a book titled "Quotes That No One Ever Said."

Not a book but..... http://en.wikiquote.org/wiki/List_of_misquotations


Steve.

 

[graywolf]

As to film quotes, there often are various cuts of a movie. I have seen one version where Bogart, not Bergman, said that. The DVD I have has the tag end of that scene where he said that cut off. If that was the only version I had seen, I would think the quote was wrong, but I know better.

I do not in fact know if Churchill ever said that but I have seen many attributions of it to him, and only a few self appointed internet experts who say he did not say anything like that.

In fact there are many SAIE's who contribute nothing to a discussion, but have to jump in there and correct every misspelling, error in grammar, they think they see. What difference does whether or not Churchill actually said that make to my point the the different viewpoints about 1:50 are probably just differences between British and American usage? And, that as such there is no use getting upset about it?

And, like the comment that Bergman never said that, the quote is actually attributed to Bogart's character Rick, the person doing the corrections is almost always proving themselves an idiot. Unfortunately, such comments make people not want to post their opinions about something because they may be attacked by some SAIE.

Please, if you want to argue with the point I was making, feel free to do so. But if you are complaining about the editing, I charge $250/page for editing, PayPal me that amount and I will happily check my quotes, spelling, and grammar and make any needed changes. If you are not willing to pay that, STFU.

 

[mawhin]

As Abraham Lincoln once said, the internets is full of self appointed experts...

And misquotes.

 

[Gerald C Koch]

The internet is far too valuable for it to be filled with misquotes, misinformation, ... Once something gets established on it then it is there forever. It has been estimated that on average there is at least one significant error in every Wikipedia entry. Where do most people go first for information?

OT Tolerance to error has been around at least as long as Virgil, "Fama, malum qua non aliud velocius alium." "Rumour, than whom no other evil thing is faster." Of course in today's world where children are given trophies for participation rather than excellence why should anyone care.

 

[lxdude]

But if you are complaining about the editing, I charge $250/page for editing, PayPal me that amount and I will happily check my quotes, spelling, and grammar and make any needed changes.

No need. They did it for you!

If you are not willing to pay that, STFU.

Good luck trying to get anyone to STFU unless you're a moderator. I think a statement like that is more distracting than the offense of unsolicited correction.

As this could be considered an unsolicited correction too, I guess I'll be told to STFU. But please don't, as it will only distract further.

 

[Steve Smith]

But if you are complaining about the editing, I charge $250/page for editing, PayPal me that amount and I will happily check my quotes, spelling, and grammar and make any needed changes. If you are not willing to pay that, STFU.

You should edit your own text for free. Only charge to do other people's!

What does SAIE mean?


Steve.

 

[Diapositivo]

I only charge $180/page for double reading, orthographic corrections, and grammar polishing, a nice Italian flair is added to your prose for free. For a measly additional $60 I can turn the text into a politically correct one (all the "dirty" will be rendered as "less clean" and all the "bastard" will become "of unknown descent" et coetera).

I accept PayPal and wire transfers. Bulk discounts available.

If interested, please contact me through private mail.

Fabrizio

 

[lxdude]

You should edit your own text for free. Only charge to do other people's!

What does SAIE mean?


Steve.

Second paragraph of the same post.