Consensus on the notation of dilutions

[Photo Engineer]

Kodak uses similar notation for Dektol.

PE

 

[Craig Swensson]

Okaaay, so what is the answer to the OP

 

[Steve Smith]

I have always thought of it as ratios, with 1:31 yielding 32 parts

So have I but not everyone agrees with us!


Steve.

 

[Juri]

I don't see why should we use 2 symbols for the same thing and limit ourselves with the "ratio" meaning.

For me 1:10 is 1 part of total of 10 parts. 1+10 is 1 part plus 10 parts. Simple.

 

[Steve Smith]

For me 1:10 is 1 part of total of 10 parts. 1+10 is 1 part plus 10 parts. Simple.

Not always simple though.

Sometimes you see "dilute 1:1 with water". Does that mean you don't add any water?!!

To me it means a ratio of one part developer (or whatever) to one part water.


Steve.

 

[Steve Smith]

Okaaay, so what is the answer to the OP

The OP asked "I just wanted to know if there's a consensus among you fine people".

I think the answer is no!


Steve.

 

[dnjl]

I just wanted to stirr up a little war, that's all . Watch out for my next topic, "Is digital better than analogue?"

Seriously though, thanks for the replies. Evidently, there is no consensus, so that's that.

 

[cmacd123]

There was no consensus the last time this was asked about a year ago either.

Cose as we can get is a slight preference for the x+y notation rather then the x:y for normal mixing instructions, and an understating that 1:1 may not mean any dilution at all to some folks, particularly chem majors who have previously encountered another iterpretaion.

We can also all probably agree that many Kodak publications use something like 1:3 to mean one part developer mixed with 3 parts water. and so can register this as a Kodiakian reference.

 

[Vaughn]

It has been fun. One thing, though, one does not usually pronounce the ":". So if I write "1:1", I will still say to students "one to one", which is, for example, short for one part Dektol to one part water. So it is never a problem when talking to students.

Even my written instructions on the wall in the developing room are written out as "one part Dektol to one part water"...as most would be totally confused to even know what the ":" means in any context! And I even write out 8 oz of Dektol to 8 oz water, because going from 1:1 to 8:8 is a stretch for some! One should see how their eyes glaze over when talking about fractions (when cutting window mats)!

 

[Kirk Keyes]

Strictly speaking 1:50 and 1+50 mean the same to me and to most chemists and technical people. Same goes for 1:49 and 1+49..

1:50 gives 51 parts and 1:49 gives 50 parts. It is normal to mix up to a given total such as 50 parts or 10 parts.

So, a 10% solution is 1:9 or 10 ml of A and 90 ml of B.

PE

As a chemist, I disagree.

1:50 is a ratio and it equals 1+49, which notes the parts used in preparing the solution.

Personally, I prefer the use of "dilution factor", which would be a "50 dilution factor" for the example I've just given above.

 

[Steve Smith]

As a chemist, I disagree.

1:50 is a ratio and it equals 1+49

As a normal person, I disagree with your disagreement!

If 1:50 is a ratio (which is how I see it) I would think of it as one part to fifty parts. The difference is that I see the fifty parts as being of one thing, you see it as being the total.

I don't think there will ever be any agreement on this!


Steve.

 

[Vaughn]

Kirk, in the case you described, "1:50" is not a ratio. The way you use it must be called something else besides a ratio -- a dilution factor or whatever you wish to call it..but not a ratio.

By the definition of a ratio (I checked out many online definitions), 1:50 means for every one of something there are 50 of another. But by what you are saying, chemists do not use 1:50 as a ratio, but as a symbol which means 1 in 50.

Thus if there is one boy and three girls, the ratio of boys to girls is 1:3 (or 1+3). The dilution of boys into the total group of people, by yours (and chemists you work with) use of the symbol ":", is 1:4 -- one boy in a group of 4 people. The ratio is not 1:4.

 

[removed account4]

i think the only thing that matters is if someone is consistent in what they do
if they do 1 part and 49 parts or 1 part and 50 parts
and their results are to their liking, that is all that counts.

 

[TareqPhoto]

In fact i always prefer to go with "+" term than say ":", i take it as both are the same, but now i read this thread i see there may be different or the same.

Well, if i will ask questions about dilutions then i will ask you people with + not with :, i want to stay with one symbol and not be confused.

Why not using 1+50=51, so we know that it is 51 total not that it is 1:50=1+49 so the total is 50, this really will make nonsense for some people like me noob, i have one developer that has many dilutions options to use, so i can't be clear with + or :, I am not a chemist so i will not be so strict to some rules or symbols meanings.

 

[Photo Engineer]

Kirk;

Look at the reference I gave to the definition of "ratio". It is, as you say something like 1:50 but each number is a part, and neither is the whole.

PE

 

[Sirius Glass]

It never ceases to amaze me that the simple mathematical and chemical concept of ratios can baffle people so much that they cannot understand the 1:4 as in 1 part dry Vermouth to 4 parts Bombay Sapphire Gin stirred, not shaken to make a proper and perfect Martini can be turned into the wretched stomach churning 1 part dry Vermouth into 3 parts Bombay Sapphire Gin [which is something almost as abominable as a "Vodka Martini shaken, not stirred"!1]. Therefore it is little wonder that children have trouble with Algebra and Chemistry when their parents cannot even mix one of the simplest bar drinks!

1What Ian Flemming did to the Martini has to be one of the greatest crimes foisted on mankind!

 

[Tony-S]

Ilford got it right. Kodak got it wrong and has screwed a lot of people up. Heck, even Ansel Adams used the Kodak method!

Mathematically, ratios are dilution factors, so a 1:3 is the same as "one divided by three". Otherwise, we would screw all of our students up when we teach them dilution problems. So...

1:1 is undiluted
1:2 is one part to one part
1:3 is one part to two parts
1:10 is one part to nine parts

The plus method is unambiguous.

 

[tkamiya]

I think the cows came home... you guys can stop now.

 

[dwross]

This has been the most fascinating thread! I would never have believed dilution notation could be controversial. It's gotta be something deep brainstem meta. Like "values." My poor brain can't see the tiniest glimmer of logic that could make 1:1 a stock solution. It simply has to mean one part stock plus one part water. But, obviously, there's no "simple" to it. The lesson for me when I write will be to avoid notations (certainly colons) altogether and spell things out word for word.

 

[Vaughn]

Mathematically, ratios are dilution factors, so a 1:3 is the same as "one divided by three".

Really?

Mathematically, what is the ratio of & to $ below:

& $$$

hint: it is not 1:4

Dang, there are the cows! Time to go!

 

[Tony-S]

My poor brain can't see the tiniest glimmer of logic that could make 1:1 a stock solution. It simply has to mean one part stock plus one part water. But, obviously, there's no "simple" to it. The lesson for me when I write will be to avoid notations (certainly colons) altogether and spell things out word for word.

When we titrate virus stocks in my lab, we start with undiluted cell culture medium from which the viruses are harvested. This is 1:1 (10^0). We then make a log10 dilution series to determine endpoints, which allows us to determine how much virus is in each milliliter of culture medium. Thus, on the plates of cells we have:

1:1 (10^0) (undiluted cell culture medium)
1:10 (10^-1)
1:100 (10^-2)
1:1,000 (10^-3)
1:10,000 (10^-4)
1:100,000 (10^-5)
1:1,000,000 (10^-6)
1:10,000,000 (10^-7)

These 10-fold (log10) dilutions require the serial transfer of 1 volume of each dilution into a tube containing 9 volumes of the culture medium. Thus, they are 1:10 dilutions, or 1+9 dilutions.

Really?

Yes, really.

 

[Sirius Glass]

It's gotta be something deep brainstem meta. Like "values." My poor brain can't see the tiniest glimmer of logic that could make 1:1 a stock solution. It simply has to mean one part stock plus one part water.

This guy also sees the faulty logic of 1:1 being stock solution. Those that do not get it have spent too much time sniffing the Hypo!

Now that the cows are home the real BS will begin about 1:1 being stock solution! : pew!:

 

[removed account4]

as i said earlier, if you mix your chemistry this way
and you don't have trouble ... then by all means continue
but i don't mix things the way you do, and never have

(sprint photochemistry says on their bottles
for 1L of solution mix 1 (stock) to 9 ( water ) )

When we titrate virus stocks in my lab, we start with undiluted cell culture medium from which the viruses are harvested. This is 1:1 (10^0). We then make a log10 dilution series to determine endpoints, which allows us to determine how much virus is in each milliliter of culture medium. Thus, on the plates of cells we have:

1:1 (10^0) (undiluted cell culture medium)
1:10 (10^-1)
1:100 (10^-2)
1:1,000 (10^-3)
1:10,000 (10^-4)
1:100,000 (10^-5)
1:1,000,000 (10^-6)
1:10,000,000 (10^-7)

These 10-fold (log10) dilutions require the serial transfer of 1 volume of each dilution into a tube containing 9 volumes of the culture medium. Thus, they are 1:10 dilutions, or 1+9 dilutions.



Yes, really.

 

[tkamiya]

Mooooooooooooooooooooooooooooo....

 

[Gerald C Koch]

This thread could have been the script for the old time radio show It Pays To Be Ignorant. Each week the panel would belabor such questions as "What is usually served in a teacup or What is a breadknife used for?"