Question about questions about iodized salt

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wetmanNY

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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?
 
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.
 
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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?
;)
 
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.
 
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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?
 
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;) )
 
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.
 
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?
 
Oh sure, why not?

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
 
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).
 
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