...although it appears clumsy, it is at least unambiguous:

"dilution: neat" might be a more logical way of expressing it in certain contexts.

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Note added at 4 hrs (2006-05-03 14:29:17 GMT)
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Oh, I SEE what you mean now!

In fact, I've always understood 1:1 dilution as being in fact 100% of the substance, but I see the logic in what you're saying, and of course it is uttterly contradictory!

I think many people must believe like me that 1:1 means 'undiluted', and NOT a 50% solution!

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Note added at 4 hrs (2006-05-03 14:58:36 GMT)
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Now here's something interesting I found on a French site:

Dilution (voir également la commande de Probabilié)

Des dilutions sont préparées dans un flacon de mesure. Un volume témoin défini est présenté dans le flacon et composé à la marque avec de l'eau distillée.



Table de dilution

Table de dilution
F = 2
F = 4
F = 5
F = 10 Volume témoin présenté dans le ballon de mesure de 50 ml
25 ml
12,5 ml
10 ml
5 ml

Facteur de dilution
F = 2
F = 4
F = 5
F = 10 Proportions
échantillon de 1 part de + dist 1 part. l'eau
échantillon de 1 part de + dist 3 parts. l'eau
échantillon de 1 part de + dist 4 parts. l'eau
échantillon de 1 part de + dist 9 parts. l'eau


F = volume final (flacon de mesure) / volume témoin.

OBSERVATION : Le ratio de dilution 1:1 est souvent
incorrectement pris pour être le ratio d'un part d'échantillon + 1 part d'eau distillée. Il se rapporte à l'échantillon non dilué.


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Note added at 4 hrs (2006-05-03 14:59:56 GMT)
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Here's the URL for that:

http://www.hach-lange.fr/shop/action_q/services;analytical/l...

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Note added at 4 hrs (2006-05-03 15:08:19 GMT)
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Here are a couple more, and I think I'm beginning to see a pattern here. It's easy to see that 1/1 means undiluted, as would be very common in French at any rate. Hence why it seems as if there may be confusion between 1/1 and 1:1.

CHAPTER

concentration for undiluted (1/1) and 1/4 runs. ... Dilution 1/1. 0. 400000. 800000. 1200000. 1600000. Reactor 1. Reactor 2. Reactor 3. Dilution 1/2 ...

etd.lsu.edu/docs/available/ etd-0413102-142601/unrestricted/CHAPTER4.pdf


Notes:

Undiluted. 1:2. 1:4. 1:8. 1:16. Reactive. Reactive. Reactive. nonreactive. nonreactive. 2. (Und.) 1:1. 1:2. 1:4. 1:8. 1:16. Report ...

www.safetycatheters.com/ds/ technicalCenter/inserts/0212013(0604).pdf

But the sites that support this view seem to be pretty thin on the ground, more seem to view 1:1 as being 50% like you do, Jorgen.

What a potential minefield of ambiguity in something as crucial as this!



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Note added at 1 day4 hrs (2006-05-04 14:57:29 GMT)
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Here's an interesting photography link where they discuss this very question:

http://photo.net/bboard/q-and-a-fetch-msg?msg_id=002ZFy&tag=