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# Thread: Consensus on the notation of dilutions

1. Behind all this is some logic that gets missed. Say you're mixing a developer 1:100 (1+99) and need 1 litre, then you use a small accurate measure for the 10ml then pour this into a larger measure and then make it up to 1000ml (1 litre). This larger measure isn't likely to be accurate enough to measure 1010ml of 1+100.

Ian

2. Originally Posted by MattKing
Like I said, great entertainment!
Tons of fun!

A ratio of 1:1 meands life size in our case FS - Full strnght - as no dilution (or concentration) is taking place...
Not following the logic of that one! LOL! In this case, 1:1 means that for every one unit of something (for example in a drawing) there is one unit of another thing (such as of the real item represented by the drawing). FS means full scale, not full strength...

But in spite of this silliness, Ralph nailed it -- good communication is the key! And I am afraid that Ian's last post fails the good communication test.

3. From Wikipedia:

"Dilution ratio
Ratios are often used for simple dilutions applied in chemistry and biology. A simple dilution is one in which a unit volume of a liquid material of interest is combined with an appropriate volume of a solvent liquid to achieve the desired concentration. The dilution factor is the total number of unit volumes in which your material will be dissolved. The diluted material must then be thoroughly mixed to achieve the true dilution. For example, a 1:5 dilution (verbalize as "1 to 5" dilution) entails combining 1 unit volume of solute (the material to be diluted) + 4 unit volumes (approximately) of the solvent to give 5 units of the total volume. (Some solutions and mixtures take up slightly less volume than their components.)
There is often confusion between dilution ratio (1:n meaning 1 part solute to n parts solvent) and dilution factor (1:n+1) where the second number (n+1) represents the total volume of solute + solvent. In scientific and serial dilutions, the given ratio (or factor) often means the ratio to the final volume, not to just the solvent. The factors then can easily be multiplied to give an overall dilution factor.
In other areas of science such as pharmacy, and in non-scientific usage, a dilution is normally given as a plain ratio of solvent to solute."
(end of citation)

In photographic processes, 1:50 means that in a total volume 50 units, 1 unit will be the developer (or other agent) and the rest (49 units) will be water (or other solvent).

A long time ago, Kodak decided to avoid any misunderstanding by adopting an additive notation, such as 1+49 (which is basically the same as the 1:n+1 notation mentioned a above). Kodak's notation is crystal clear: 1 unit of the principal agent is added to 49 units of solvent, whichs gives a total volume of 50 units.

1:50 (1 to 50 or 1 in 50) means that the agent is 1/50 of the total volume of 50, from which we can infer that the solvent is 49/50 of the total. As Kodak expresses, 1+49 to make up 50 units.

Similarly, if we want to use the agent undiluted, the scientific notion would be 50:50 (50 units of the total volume would be the agent and there would be no solvent. Thus, the reduced fraction 1:1 means undiluted (that is, 1 unit of agent plus 0 units of solvent) or 1+0, which is usually called "stock", which means straight out of the bottle or as initially prepared from dry ingredients according to the manufacturers basic formula.

4. Originally Posted by Vaughn
FS means full scale, not full strength...
In photography some manufacurers use the term F.S. with developers that can be use at Full Strenght or also diluted 1+1 and 1+3 etc, but yes FS is full scale in other photographic applications like copying, but we can have a ratio in this case so 1:1 is also applicable

I did qualify because we don't use a ratio like 1:1 with dilutions as it's meaningless, how can you have a one sided ratio when there's no dilution or concentration

What's important is accuracy and some manufacturers used to put both 1:10 (1+9) or similar on their bottles/datasheets to prevent inaccuracies.

Ian

5. Originally Posted by Benoît99
A long time ago, Kodak decided to avoid any misunderstanding by adopting an additive notation, such as 1+49 (which is basically the same as the 1:n+1 notation mentioned a above). Kodak's notation is crystal clear: 1 unit of the principal agent is added to 49 units of solvent, whichs gives a total volume of 50 units.

1:50 (1 to 50 or 1 in 50) means that the agent is 1/50 of the total volume of 50, from which we can infer that the solvent is 49/50 of the total. As Kodak expresses, 1+49 to make up 50 units.

Similarly, if we want to use the agent undiluted, the scientific notion would be 50:50 (50 units of the total volume would be the agent and there would be no solvent. Thus, the reduced fraction 1:1 means undiluted (that is, 1 unit of agent plus 0 units of solvent) or 1+0, which is usually called "stock", which means straight out of the bottle or as initially prepared from dry ingredients according to the manufacturers basic formula.
Unfortunately Kodak in the US seemed to think differently Someone there got confused by the + and the :

So in British publications Kodak would say 1+1 & 1+3 and in the US 1:1 & 1:3 and mean the same thing, go figure that one out. The : symbol is used in maths (Mathematics) as a Ratio not as a + (plus) sign

Ian

6. If you change definitions depending on what field you are working in, you are ambiguous.

From Wikipedia:

In mathematics, a ratio is a relationship between two numbers of the same kind[1] (e.g., objects, persons, students, spoonfuls, units of whatever identical dimension), usually expressed as "a to b" or a:b, sometimes expressed arithmetically as a dimensionless quotient of the two[2] which explicitly indicates how many times the first number contains the second (not necessarily an integer).[3] In layman's terms a ratio represents, simply, for every amount of one thing, how much there is of another thing. For example, supposing one has 10 pairs of socks for every pair of shoes, the ratio of shoes:socks would be 1:10 and the ratio of socks:shoes would be 10:1.

I took a modification of this for my above post.

This shows you that some people do not know that things are often wrong on the internet. A ratio is a ratio regardless of usage. Math defines the term. The above, in my post here and previously, is the correct definition.

You do what you wish. You can even define things any way you wish. That does not make them right. I suspect an errant photographer or poster here probably edited the post on dilution ratios.

PE

7. I've never worked for Kodak, but the way I was taught in undergrad is the same as PE has it. 1:49 is the same as 1+49. Though most of the time we did things by % volume.

8. Concerning the notation for dilution; as a fellow student in chemistry was fond of saying, "That's not ambiguous that's amtriguous."

9. Bethe;

10% is 1:9 or 1 ml in 9 ml etc. So, yes I understand. I do most things by weight as the volume changes when you mix many things together. I also measure many viscous things which are difficult to measure by volume. Weight is easier. I must remind anyone who wishes to be critical of my using weight, consider that I usually measure in the dark when measuring out emulsions and 10% gelatin for addition to an emulsion. So, weight is handy.

But, thanks for the confirmation. I think often that no one these days is properly trained in math, or has ever taken a real lab course.

PE

10. But, thanks for the confirmation. I think often that no one these days is properly trained in math, or has ever taken a real lab course.

PE
I suck at math, but I do have a BS in bio (we had to take chemistry for that, too), a MS in Forensic Science, and worked in a lab for 14 years.

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