Iodophor Dilution

[WildaYeast]

I've been using iodophor for a while, at 1ml per litre.

I was reading some post that took me to this page where the author cites a manufacturer as recommending a concentration of 12.5 ppm.

Unless I've screwed up my maths (possible, but did a bit of head scratching), 1ml per litre = 1,000 ppm, which is about 80x as strong as I need, so I should be adding about 0.0125ml per litre, which is a ridiculously small amount.

The AHB wiki on iodophor also mentions 12.5 ppm and gives a dilution of 10ml per 10 litres, so consistent with what I've been doing.

So, just trying to understand the maths here. I'm quite certain there are 1,000 ml in 1 litre and ppm does mean parts per million, so, where's the error....

 

[TSMill]

You are not starting with 100% pure sanitiser though, the required concentration is 12.5ppm of titratable iodine, suggesting idophhor is ~1.25% iodine to start with.

 

[mwd]

The bottle I have does not state the ingredients and concentrates on the label but does mention phosphoric acid.
I always make up to 1ml per litre and never had a problem so far except it makes glass bottles slippery.

 

[fcmcg]

The bottle I have does not state the ingredients and concentrates on the label but does mention phosphoric acid.
I always make up to 1ml per litre and never had a problem so far except it makes glass bottles slippery.

The bottle i have is from the G&G...
It states a dilution of 1:1000 say 1ml in 1 litre of water will give you 12.5 ppm solution....
So with my year 10 science degree , i reckon that what this means, is that with with so much water ,and so little iodopher , for every million parts of water , there is only 12.5 parts of iodopher.... :unsure:
Cheers
Ferg

 

[warra48]

This is the key sentence in the first link in the OP.

"Please recall that we are adding 1 ml. of the 12.5 ppm solution to the sample, not 1 ml. of undiluted iodophor."

That confirms what's been posted above by the 3 earlier replies.

 

[beerdrinkingbob]

This is the key sentence in the first link in the OP.

"Please recall that we are adding 1 ml. of the 12.5 ppm solution to the sample, not 1 ml. of undiluted iodophor."

That confirms what's been posted above by the 3 earlier replies.

Huh?? Have you been drinking or have i drunk to much already :icon_drunk:

I think Ferg summed it up, they way yours sounds your suggesting we are using a highly watered down solution, only to water it down some more, from what i have read the 12.5 is after we dilute it.

Edit : just read the bottle and the first sentence states "dilute1:1000to give a 12.5 ppm solution"

 

[fcmcg]

This is the key sentence in the first link in the OP.

"Please recall that we are adding 1 ml. of the 12.5 ppm solution to the sample, not 1 ml. of undiluted iodophor."

That confirms what's been posted above by the 3 earlier replies.

I reckon your right , bloke ..the key is in the OP...who states that he thinks it's a ratio of 1ml per litter is equal to 1000ppm...that's where I reckon the confusion is...it's actually that ratio will give you 12 ppm

 

[matr]

Going by the MSDS for the stuff it is about 10% Iodine, between 10% - 30% Phosphoric Acid & 60% - 80% Non Haz ingredients.

As seen here: Link

Don't know if that makes any difference..

Cheers, Mat.

 

[beerdrinkingbob]

I'm out, i think my head just exploded, when we have the final answer let me know :blink:

 

[MHB]

I can't speak for other shops products but the one I stock, has 120g/l Phosphoric Acid and 20g/L of Iodine (should say what the concentrations are on the label).
Happily enough 1mg/L is the same as 1ppm, if you wanted 1 Litre (1000ml) of 12.5 ppm starting with 20g/L of Iodine.
1g = 1000 mg, we have 20g so we have 20,000 mg/L

C₁V₁=C₂V₂ (C is Concentration and V is Volume) (my old favourite)
20,000*V₁ = 12.5*1000
V₁ = (12.5*1000)/20,000 = 0.625mL

It's the Iodine concentration that's the important part, it's what kills bugs, the Phosphoric acid is there to make it Iodine soluble. Having said that, the manufacturer recommends 1.5mL/L for cleaning Stainless Steel dairy systems and certainly doesn't regard it as a no rinse sanitiser.
Hope that helps

MHB

 

[AndrewQLD]

Phos acid is a sanitizer though isn't it?

Andrew

 

[WildaYeast]

The suggestion that the iodophor isn't pure, that it's already diluted, makes sense.

Gotta agree with BDB -- the quote from the first link in the OP doesn't apply here (was just related to his taste threshold experiment)

The MSDS at 10% got me from 1,000 ppm to 100 ppm, much closer at least.

Thanks MHB -- yours arrived as I was writing this. That makes heaps of sense and comes up pretty close to what the first link in the OP said -- he could back off to about 2/3, which is what your answer says at 0.6ml per litre rather than 1ml per litre.

I got mine in a bulk buy, so no label, etc. Imagine I'm fine at 1ml per litre, but have read before that more concentrated isn't better; greatest efficacy is at the right concentration.

Was mostly wanting to know where my maths were wrong...

 

[MHB]

It may perhaps be but not at 75ppm (what you would get from the above dilution) there just isn't enough there to be effective after you dilute the stock solution over 1,000 fold.
Sorry I wasn't clear, it will also remove beer stone and some other stubborn deposits, also reacts with Stainless Steel forming a Chromium Phosphate layer that is tough and resists build up of soils and attack from other chemicals. Phosphoric acid doesn't just make the I₂ soluble (any acid will do that); it's the right acidifier to choose for Stainless systems.

MHB

Wilder
0.625 mL only applies for the starting concentration in the equation (20g/L), if yours was 10g/L you would need 1.25 mL/L to get the same amount of I2 in there.
It really does pay to know the answer, especially in something this concentrated. The difference in the I2 concentration I’ve sited is 100%, when we are talking about powerful industrial strength chemicals that’s 100% is too much error.
M

 

[AndrewQLD]

Great, wasn't really paying attention to the maths, and I should have, so your post is crystal clear now.

Cheers
Andrew

 

[beerdrinkingbob]

but have read before that more concentrated isn't better; greatest efficacy is at the right concentration.

I listened to a podcast regarding correct use of Iodophor, it was interesting, it was the March 22, 2007 - Sanitizing with Iodophor episode -
Link


What i took out of it at a glance is get it right, if it's too Strong it can be toxic, so get your measurements right, don't just tip some from the bottle into a bucket. If you deliberately make it stronger to try and get a better result you will have rinse and you have just wasted your time <_<

 

[brocky_555]

Is there a big issue if you make up the solution a bit stronger say 1ml to 500ml? does this do anything detrimental to the solution ?

 

[felten]

Too strong and it's not no-rinse anymore. Which is exactly what bob said one post up.