Question about questions about iodized salt

[wetmanNY]

So if potassium iodide (KI) in U.S. iodized salt ranges 20 to 40 parts per million in the box, --that's the range, isn't it?-- what part per million range does that represent for the iodine?

At, say, one teaspoon per gallon, could anyone work out for me what parts per million concentration of iodine are those people worrying about?

My math isn't that steady...

Let's not discuss in this thread the value of salt one way or the other...

just how much iodine are we actually talking about here?

[pinballqueen]

Common sense would tell me that if KI is present at 40 ppm, then, if it were present as free iodine (which would suck.... ew, blue-black salt...)...hmmm....(grabs calculator and copy of the periodic table... Potassium is #19, Iodine is #53.... which would mean that 2/3 by weight of KI is iodine...).... it would be about 26 or 27 ppm in the table salt. I could be wrong, though.

As far as adding it to the water, man that would really make the ppm look really small, wouldn't it? However, you would have to take into consideration that it's potassium (or sometimes sodium) iodide, rather than free iodine, and that there may also be iodides in the tap water adding to the mix. Compounds rarely exhibit the same qualities as their component elements, so free iodine could cause a different reaction than the same concentration of iodine, just in the form of potassium iodide, would in your tank. After all, look how much chlorine is in table salt, and I don't think anyone would think of putting a gas-line of chlorine into their tank, would they? Where chlorine is harmful and caustic, and sodium would actually light on fire and spin around if you tried to put it into water, sodium chloride is actually pretty healthy for your tank.

[aquariaddictus]

There is no iodine in KI, nor is there free chlorine in table salt. Iodide is I-, while iodine is I2; chloride is Cl-, chlorine is Cl2, and neither would dare covert from the more stable salt form to the gaseous form. The terms aren't interchangable.

I've never seen iodide present in a municipal or well water, although it wouldn't surprise me on the coasts (I have noted bromide in California).

"So if potassium iodide (KI) in U.S. iodized salt ranges 20 to 40 parts per million in the box, --that's the range, isn't it?-- what part per million range does that represent for the iodine?"

PBQ's numbers are right - KI is 73% iodide, so the range of IODIDE, not iodine, is 14.6 - 29.2 ppm.

PBQ - what are you doing up so early?
;)

[aquariaddictus]

Okay - this took me a minute, but I think it's what you wanted. KI weighs 3120 kg per cubic meter (202,884 teaspoons).

3120kg/202,884tsp = .015etc kg, or 15.38 grams per teaspoon. So, 15.38 grams, or one teaspoon, per gallon = 15.38 grams per 3.7854 liters = 4 ppm as KI.

SOOOOOOOOO, adding STRAIGHT KI to a tank at a rate of one teaspoon per gallon gives you 4 ppm KI. AND one tsp/gallon is a lot. AND if table salt is only 20-40ppm KI..................assume the worst - 40ppm - (40 x 4)/ one million = 0.00016 ppm KI. Oooops, factor in the 73%: 0.00016 x 0.73 = 0.000119 ppm iodide :eek:

Why are we talking about this?????:confused: I need a cup of coffee.

[wetmanNY]

Okay, AquariaCentralites, this is what an amateur gets so far:

"In the U.S. table salt is commonly iodized using sodium iodide (NaI) or potassium iodide (KI) at concentrations ranging 20 to 40 parts per million in the dry salt. That iodide is not to be confused with iodine (I2). The molar weights of the potassium and the iodide are 19 and 53, so the potassium iodide is actually 73% iodide by weight. That gives a range of 14.6 - 29.2 ppm iodide in the dry salt.

"Now you use that iodized salt in the aquarium. You add a tablespoon of iodized salt for every net gallon of water. That's the equivalent of adding 15 grams of salt, which would add a range of XX to YY parts per million of iodide to the aquarium water."

Question: Is a tablespoon = 3 Teaspoons of table salt actually about 15 grams?

I'm innumerative and can't get the figures. (How did I ever get through sixth grade?) Is this the right procedure?

[aquariaddictus]

Wetman - for starters, I'm off by a factor of 1000 in my prior calculation (should have had the coffee first). PPM is defined as mg/liter. I forgot to multiply my grams by 1000. So 0.119 ppm iodide in the water is more like it, if you dosed at 1 teaspoon/gallon. Furthermore, I based the calculation on the addition of pure KI to the water and KI weighs about 15 g/teaspoon, or 45 per tablespoon (Google says so). NaCl will weigh differently. Rather than look it up, I'm going to pull out my analytical balance and weigh my Morton's and get back to you (no snide remarks about why a chemist has a balance under her bed please)

"That gives a range of 14.6 - 29.2 ppm iodide in the dry salt" - correct. However, the number will differ depending on whether NaI or KI was used. That's probably why they expressed such a wide range.

What do proponents of salt recommend? 1 tablespoon/gal or 1 tablespoon/10 gallons? - I don't have a box of aquarium salt here. I worry so little about the whole issue that I use water softener salt - $3 for 40#

Let me get a weight and redo the calculation, now that I'm awake. I'll be back. (I got thru 7th grade;) )

[aquariaddictus]

Hmmmm. I think the figure I pulled off the net for the KI weight was wrong too. Let's start from scratch with some kitchen chemistry.

One level tablespoon of Morton's salt weighs 21.5 grams by my balance. You're probably coming up with 15 grams because a tablespoon is 15 ml, and water weighs 1 gram/ml.

So, 1 tablespoon/gallon = 1 tablespoon/3.78541 liters = 21.5 grams/3.78541 liters = 5.6797grams/liter = 5680mg/liter = 5680ppm salt aded to the aquarium. If the salt contains 40 ppm potassium iodide, then of the 5680 ppm salt you just added, 40 out of every million is KI. So, (5680 x 40)/one million = 0.227 ppm (as KI). Multiply by 73% = 0.166 ppm as iodide. I think.


Or if you want to start with the range of 14.6 - 29.2 ppm:
(5680 x 14.6)/one million = 0.083ppm iodide = XX
(5680 x 29.2)/one million = 0.166ppm iodide = YY (confirming the method above where I assumed 40 ppm, then factored the 73% in at the end) So your range is 0.083 - 0.166ppm.

All in all, I have to believe it's a drop in the bucket. Does anyone use a tablespoon/gallon except in times of severe disease??

Hope this helps.

[wetmanNY]

Well, it sure helps enough to quote you at www.skepticalaquarist.com if that's okay with you, O Moderate One. Better than cribbing your calculations and passing them off as my own, eh.

So, can we inscribe on the granite block:

"In a long-term saltbath to eliminate skin parasites such as Costia or Ich, using salt generously, at a tablespoon per gallon, the range of iodide in the water would be ~0.083 - 0.166ppm."


Future discussions of iodized vs. non-iodized salt in medicating fish could begin with this firm ground point and aquariaddictus' calculations.

Math geeks and chemheads! any flaws in our thinking?

[aquariaddictus]

I'm usually only quoted using a lot of four letter words!! No royalties involved, I suppose??:D

I have a BS in Chemistry and a math minor (then there's that nursing thing), but I do wish someone would double check the calculations. Where's RTR, and MP?? Bomar?? Anyone??

Glad I could help - I just hope it's right.
judy

[RTR]

My balance is not under the bed - it is packed away in a safe place which I cannot locate at the moment - I suspect behind a head-high stack of boxes from when a family member "borrowed" some storage (2 year Peace Corp assignment).

So I sat back and let the rest of you play - I have no issues with the excellent work to date, but I haven't tried to reproduce the info. Later tonight I'l start with the weigh given and confirm the decimal places at least (playing hookey from guest at the moment - drinks before a charity ball I am not attending).

[Tempest]

I don't know about our newbies here but YOU GUYS ARE SCARING ME !!! <laughs and ducks back down out of sight.>

[RTR]

The math checks out fine at 0.166ppm of iodide from KI in iodized salt at 1 tablespoon per gallon. That assume the original concentrations were real, and the K and I weights were externally verified (I checked neither).

That would be a dandy addition to the site wetman. It will not kill the myths, but it will give the dubious a ballpark figure to use in toxicity searches.

Nice

[wetmanNY]

Whew! sidelong glance at aquariaddictus

Well, Tempest, I figured if topics like "Is this Ich on the glass?" are okay in the General forum, then we can come in here and work out the iodide* thing and appal the Newbies.

* and I thought it was iodine tch!

[aquariaddictus]

Hey, I scare myself sometimes; nothing new :p

i sure could make a lot more money using that balance for other purposes

Can we talk about thyroids now, and the REASON we have iodide in our salt?? ;)

[RTR]

Technically your are allowed to say there is iodine in potassium iodide. Chemically and in solution it is in the form of the iodide (I-), not the gas (I2). Certainly you could not say KI contains no iodine.

The term "iodine" is used differently in the lab and in everyday conversation. Nutritional discussions do not say that this or that food is rich in iodide - they say it has or is rich in iodine. In biosystems you are very rarely dealing with pure elements, you deal instead in combined forms, and you may use the element name to discuss its presence, it is not needed to specify the combined or ionic form unless there are availabilty issues - i.e., nitrite-nitrogen is not immediately available to plants, where ammonia-nitrogen and nitrate-nitrogen are accessible.

[aquariaddictus]

I guess that is the difference between strict science and everyday speak, or nutritional info. We would never analyze table salt for its iodine content, or look at sodium chloride for free chlorine. But I'm sure to the general public, it's all the same. The difference is how we 'express' it. However, if there were free I2 in table salt, or KI for that matter, you can bet no one would be adding it to fish tanks and the toxicity issue would have merit.
In anything other than something as stable as a sodium salt, I'm sure some of the iodide is present as iodate, so the calculations are far from pure.

Your point is well illustrated by iron. "Eat foods that are rich in iron". Even if you chewed on a rusty nail, you're still ingesting an oxidized form of iron, but we don't speak of it that way (although a labrat might). Maybe I've been caged too long! Our ionic balances (++ = --, on an atomic weight basis) had to be on target, and calculating using neutrals would not have accomplished that.

My math concerned me more than this technicality (did I say rusty earlier?) so I appreiciate you double checking it for me. WetMan: I'm sure you'll phrase it all to confuse the minumum number of the masses ;)

[pinballqueen]

Originally posted by aquariaddictus
"

PBQ's numbers are right - KI is 73% iodide, so the range of IODIDE, not iodine, is 14.6 - 29.2 ppm.

PBQ - what are you doing up so early?
;)

Well, I'll be doggoned! And I never even took chemistry in school.... all I know about it I learned in geology class.... I'm glad someone with real knowledge of the stuff stepped in though....

[aquariaddictus]

heheheh. Are you still taking any narcotics?? Sometimes these things pop into your mind when you're in an altered state!!

How is the boy?? Sleeping thru the nite yet? ;)
judy

[pinballqueen]

no, but he sleeps pretty much all day....

I'm getting over a rather nasty bout of food poisoning, myself...

broke my 9-year plus "no-puke" streak... so now I'm on anti-nausea drugs, but no narcotics, in fact, I haven't even touched the bottle of oxycodone the doc prescribed for me.... figured I'd save it for a migrane or something...

I have, however, been thinking pretty hard about what I'd like to do with my career. Let's face it, hotel administration isn't the most stable field in the world... was thinking about going back to school for teaching, honestly.... (I'm fairly sure a combination of new-motherhood and narcotics while in the hospital started that thought process....)

[JSchmidt]

And this is a Newbie forum! Just think what the poor beginners will expect from the main freshwater forum!

Seriously, this is a very interesting thread, and one that reminds me why I did so poorly in high school chemistry...

Jim

[wetmanNY]

The Pinballqueen's tadpole is getting dipped in at the deep end right away, eh...

"Begin as you mean to go on," my mother always said.