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# Thread: Consensus on the notation of dilutions

1. 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.

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

3. 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.

4. Originally Posted by Tony-S
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!

5. Originally Posted by dwross
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.

Originally Posted by Vaughn
Really?
Yes, really.

6. 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 ) )

Originally Posted by Tony-S
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.

7. Mooooooooooooooooooooooooooooo....

8. 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?"

9. It really comes down to this: When someone says "use it at 1:1", you cannot be sure if they mean 1 part developer and 1 part water, or just straight developer. If they say "use it at 1+1" then its unambiguous.

10. Well Tony, the mathematical and chemical definition of rations with dilution are as Wikipedia says. 1:1 is 1 part of A to 1 part of B. 1:2 is one part of A to 2 parts of B.

How hard is that to understand. Now I know why we are suffering at the hands of medical people! (JK) I have a minor in Biochemistry and my prof would shoot me if I used your methodology.

PE

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