Reef Chemistry Question of the Day #180 Lugols iodine

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#180[/HASHTAG]

Many folks use Lugols iodine as an iodine supplement for reef tanks.

What are the forms of iodine added into Lugols solution to make it?

A. I2 and I-
B. I2 and IO3-
C. I- and IO3-
D. I2
E. I-
F. IO3-

I2 = molecular iodine
I- = iodide
IO3- = iodate

Good luck!

























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[beaslbob]

the wrong one?

 

[Lynn52]

A

 

[ReefJunky]

I used to be a Histology Technician. Lugol's Iodine is a solution of elemental iodine and potassium iodide in distilled water so the answer is "A".

 

[Randy Holmes-Farley]

And the answer is...A. I2 and I-

Lugols is a mixture of I2 and I-.

Here's a recipe:

https://web.archive.org/web/2014032...ienceresearch/laboratorymethods/ucm062245.htm

Lugol's Iodine Solution
Potassium iodide (KI) 10 g
Iodine 5 g
Distilled water 100 ml

Dissolve KI in about 20-30 ml of distilled water. Add iodine and heat gently with constant mixing until iodine is dissolved. Dilute to 100 ml with distilled water. Store in amber glass-stoppered bottle in the dark.



Curiously, the I- and I2 in Lugols will combine to form a more unusual species, I3-:

I2 + I−⇌ I3−

I discuss much more about iodine and reef tanks here:

Chemistry And The Aquarium: Iodine in Marine Aquaria: Part I ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/issues/mar2003/chem.htm

Chemistry And The Aquarium: Iodine In Reef Tanks 2: Effects On Macroalgae Growth ? Advanced Aquarist | Aquarist Magazine and Blog
http://www.advancedaquarist.com/issues/april2003/chem.htm