iodine's sanitizing power (measurements)

Zh6Gbw

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Can anyone give me a sense of how much iodine would be needed to make, let's say, 3 ml of water thoroughly sanitary?
 
Can anyone give me a sense of how much iodine would be needed to make, let's say, 3 ml of water thoroughly sanitary?

This link:http://en.wikipedia.org/wiki/Portable_water_purification

suggests 12.5cm³/l of saturated iodine solution, prepared from iodine crystals, with the caveat that this may not kill giardia cysts. So it depends what you mean by "sanitary".

The article explains there are other iodine preparations available, for which other treatment rates would be appropriate.
 
The Wikipedia article seems to be speaking of ~2.92 grams of iodine per liter of water. That would leave you with about ~666 mg of iodine in an 8 oz. glass of water. By comparison the Institute of Medicine states that the RDA of iodine for an adult male is 150 micrograms.* :eek:

Actually, I made a slight error, but the true amount still seems to be massive. Let me re-do my calculations and then edit this post. Update: Correction made.


*Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001. Retrieved from http://ods.od.nih.gov/factsheets/Iodine-HealthProfessional
 
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The Wikipedia article seems to be speaking of ~2.92 grams of iodine per liter of water. That would leave you with about ~666 mg of iodine in an 8 oz. glass of water. By comparison the Institute of Medicine states that the RDA of iodine for an adult male is 150 micrograms.* :eek:

Actually, I made a slight error, but the true amount still seems to be massive. Let me re-do my calculations and then edit this post. Update: Correction made.


*Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. Washington, DC: National Academy Press, 2001. Retrieved from http://ods.od.nih.gov/factsheets/Iodine-HealthProfessional


No. The solubility of iodine in water is about 1g in 3.45l water at 20C, according to Wiki.

Don't make the error of assuming all the crystals dissolve, when the solution is made up. If you read on, in the original link I posted, you will see they can be reused. The idea, apparently, is to get a saturated supernatant solution, which you decant to use.

Using the above solubility number, I get a saturated solution containing ~0.0003 g/cm³, which when added to water at the concentration they suggest (12.5g/l) gives you a final concentration of ~3.6mg/l.

On the question of iodine dose for water purification vs. recommended dietary maximum, there is no reason why these need be aligned, since the short term risk from waterborne disease easily trumps long term overexposure, provided iodine is not used as a long term method of water purification. Read more here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1638306/
 
What confuses me is the fact that there's going to be a lot of iodine crystals sitting on the bottom of the supernatant solution. How does one work with that in the future, after having used some of the liquid for some time? It just seems like a big complication to me and it's making my head spin.

Thanks for the measurements, by the way.
 
What confuses me is the fact that there's going to be a lot of iodine crystals sitting on the bottom of the supernatant solution. How does one work with that in the future, after having used some of the liquid for some time? It just seems like a big complication to me and it's making my head spin.

Thanks for the measurements, by the way.

I didn't measure anything. I dd a few calculations, that's all.

There's nothing at all hard about this. The point about a saturated solution is that you only know you've got one when you have surplus solid left over. Provided you have enough of the remaining solid, you can make up with fresh water when you have used some, shake it up to dissolve some more and, provided there are still at least a few crystals lefts at the bottom, you will know you have, once again, a saturated solution.

The concentration of a saturated solution will be the same every time, for a given temperature. (Of course, as it get warmer, water dissolves more, so this could be a source of variation. I imagine this might come in handy if you are travelling somewhere basic, having no measuring equipment and want make sure you use the right dose to protect yourself.
 
Can anyone give me a sense of how much iodine would be needed to make, let's say, 3 ml of water thoroughly sanitary?
This might be a better fit for the chemistry forum, I don't understand the biological component.
 
This might be a better fit for the chemistry forum, I don't understand the biological component.

Bacteria...

The measurement discussed in this thread works out to be several drops per liter of water. What I'd like to know is does its sanitizing action increase with an increase in its concentration or is its sanitzing action maxed out in the measurement discussed.
 
The commercial product Potable Aqua will sterilise about a litre of water with one tablet.
http://www.amazon.co.uk/Potable-Aqua-Water-Treatment-Tablets/dp/B001949TKS
The bottle contains 6 grams of tablets and there are 50 tablets.
Each tablet is 6.68 % iodine.

So
6000 mg
Divided by 50
Divided by 100
Times 6.68

Is approximately 8 mg per litre.

The amount varies according to the source of the water.
To be sure, you need to buy a proprietary product and follow the instructions.

The amount of iodine you need in your diet is measured in micrograms, not miligrams,
so this would be an excessive amount of iodine to ingest on a regular basis.
 
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According to this article, the Japanese consume on average 50 times more iodine in their diet than people in the US.
And some people living on the Hokkaido coast ingest 200mg per day from eating seaweed.

People in the U.S. consume an average 240 micrograms (µg) of iodine a day. In contrast, people in Japan consume more than 12 milligrams (mg) of iodine a day (12,000 µg), a 50-fold greater amount. They eat seaweed, which include brown algae (kelp), red algae (nori sheets, with sushi), and green algae (chlorella). Compared to terrestrial plants, which contain only trace amounts of iodine (0.001 mg/gm), these marine plants have high concentrations of this nutrient (0.5—8.0 mg/gm). When studied in 1964, Japanese seaweed consumption was found to be 4.5 grams (gm) a day and that eaten had a measured iodine concentration of 3.1 mg/gm of seaweed (= 13.8 mg of iodine). According to public health officials, mainland Japanese now consume 14.5 gm of seaweed a day (= 45 mg of iodine, if its iodine content, not measured, remains unchanged). Researchers have determined that residents on the coast of Hokkaido eat a quantity of seaweed sufficient to provide a daily iodine intake of 200 mg a day. Saltwater fish and shellfish contain iodine, but one would have to eat 15—25 pounds of fish to get 12 mg of iodine.

The coast dwellers are more prone to developing a disease called Hashimotos thyroiditis,
so such high levels are not recommended.
 
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The 8 mg per liter conforms to my statement of 'several drops per liter' and my last question was is the sanitizing capacity of iodine maxed out at these proportions? What if I put 8 mg in a shot glass, for example?
 
I don't know the answer to that.
A higher concentration could be less effective.
The solution as made will kill virtually 100% of bacteria within seconds.

How does iodine work as an antimicrobial?
Iodine's exact antimicrobial mode of action is not fully understood, but it is believed to be associated with its ability to rapidly penetrate the cell wall of micro-organisms[17].


Schreier et al also investigated the effects of PVP-1 on microbial cells and found that it affects the structure and functions of enzymes and cell proteins and damages bacterial cell function by blocking hydrogen bonding and altering the membrane structure. These multiple modes of action ensure the rapid death of microbes and help to prevent the development of bacterial resistance. Because the microbicidal action of iodine is related to several directly toxic effects on the cell wall, rather than through specific molecular pathways (as used by antibiotics), resistance is highly unlikely and reports of iodine-resistant strains are exceptionally rare

http://www.woundsinternational.com/made-easys/iodine-made-easy/page-2
 
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The 8 mg per liter conforms to my statement of 'several drops per liter' and my last question was is the sanitizing capacity of iodine maxed out at these proportions? What if I put 8 mg in a shot glass, for example?

DO NOT TRY ANYTHING SILLY. Iodine is an irritant and can burn the digestive tract at sufficiently high concentrations.

It is very unwise indeed to exceed the recommended concentrations of such substances arbitrarily. You could end up in hospital.
 
When I was at school we had a teacher who showed us how to make Nitrogen Triiodide.
I blame my Tinnitus on him.
 
No, it wasn't cool at all.
I think we should only have made a crystal or two,
but we caked filter pads with the stuff and left it to dry.
I don't think he was a very responsible teacher.
 
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