Reef Chemistry Question of the Day #100 Chemicals that impact ORP

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #100

Which of the following chemicals is most likely to immediately reduce a reef aquarium's ORP?
Ignore the potential for unknown impurities in them.


A. Ferrous gluconate (e.g., Seachem Flourish Iron)
B. Molecular iodine (I2, such as is present in Lugol’s iodine solution)
C. Hydrochloric acid (HCl; muriatic acid)
D. Magnesium sulfate (e.g., Epsom salt)

Good luck!




































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[birdsnest]

my answer is C

 

[DMan]

I'm going to say, all of the above. From what I've seen just about anything and everything I introduce to the tank reduced ORP. With the exception of Ro/Di top off water.

 

[spspirate]

Im going with C too.

 

[beaslbob]

a

Just to be different

 

[omykiss001]

A

It was a toss up between A and D. I would think the Mg is just going to give its electrons to the sulfate ion to become Mg2+. Given the iron in iron gluconate is bound as the 2+ form of iron assuming it's released from the gluconate chelator is a good reducing agent and should drive the ORP down as it gives up electrons to become Fe+++. I2 is an oxidizer and would raise ORP and adding HCl would drive pH lower and increase oxygens ability to be an oxidizer and raise ORP.

Good question will be interested to hear the answer.

 

[Cory]

I'm guessing iodine

 

[Steven@]

I think C will cause the immediate reaction

 

[UK_Pete]

Since no ones said it, B. Iodine is in the same group as chlorine and chlorine significantly affects ORP. To do with electron acceptors / donors and such maybe? But iodine is lower down so less reactive so maybe thats wrong!

 

[UK_Pete]

Duh - reduce the orp not increase it. Not iodine then. Ill change to ferrous gluconate

 

[Randy Holmes-Farley]

And the answer is ...A. Ferrous gluconate (e.g., Seachem Flourish Iron)

Ferrous (Fe++) is the reduced form of iron, and tends to reduce ORP. Ferric (Fe+++) is the more oxidized form.

All of the others tend to have no effect (magnesium sulfate) or raise ORP (I2, which is an oxidizer, and hydrochloric acid, which lowers pH and thus tends to raise ORP).

This has more:

http://reefkeeping.com/issues/2003-12/rhf/feature/index.htm