Reef Chemistry Question of the Day #201 Offgassing of reef tanks

[Randy Holmes-Farley]

Reef Chemistry Question of the Day #201

Which of the following elements will never come out of the water and into the gas phase above a reef aquarium in any chemical form?

A. Sulfur
B. Iodine
C. Sodium
D. Chlorine

 

[sghera64]

Reef Chemistry Question of the Day #201

Which of the following elements will never come out of the water and into the gas phase above a reef aquarium in any chemical form?

A. Sulfur
B. Iodine
C. Sodium
D. Chlorine

Sodium

Sulfur leaves as a stink. Chlorine has a few conceivable gaseous forms that would be in very low proportions (HCl - way low at Reef pH and Cl2 which might require some redox chemistry). Iodine is a group VII element like Cl so IBID. But sodium. The only gaseous form I know of would require extremely high temperatures - like in sodium MH lamp to vaporize.

 

[bgoldb]

My guess would be Iodine.

 

[Alfrareef]

O would also go for Iodine...

 

[Orcus Varuna]

C. Sodium

 

[GMay]

sodium

 

[CNDReef]

C

 

[Heliarc19]

B? Eh...

 

[120reefkeeper]

C.

 

[jason2459]

Sodium

Sulfur leaves as a stink. Chlorine has a few conceivable gaseous forms that would be in very low proportions (HCl - way low at Reef pH and Cl2 which might require some redox chemistry). Iodine is a group VII element like Cl so IBID. But sodium. The only gaseous form I know of would require extremely high temperatures - like in sodium MH lamp to vaporize.

Molten sodium for solar power storage is very cool. Well, not cool...

 

[Salty1962]

Iodine

 

[CarterJ]

Sodium

 

[oceanfreak09]

Sodium

 

[Keiffer the reefer]

Sodium

 

[Martin Kuhn]

B
Iodine is "used up" but not volatile

 

[Reefer1978]

C. Sodium

 

[Randy Holmes-Farley]

Any more takers before I give the answer?

 

[beaslbob]

sodium

 

[beaslbob]

Any more takers before I give the answer?

now tell us

 

[Randy Holmes-Farley]

And the answer is...C. Sodium

The only form sodium ever takes in a reef tank is the sodium ion, Na+.

It is nearly always lose in the water, but some may be loosely bound to another ion, either organic (such as acetate) or inorganic (such as chloride), but ions and combinations of ions do not enter the gas phase from water. They just stay in the water.

Incorrect choices explained...

A. Sulfur. There are many organosulfur compounds that come off of a reef tank into the air. The smell of the ocean is often attributed in part to dimethylsulfide, CH3-S-CH3 :

https://www.livescience.com/4313-key-smell-sea.html

"Scientists had long known that bacteria could be found consuming decay products and producing a gas called dimethyl sulfide, or DMS, in places where plankton and marine plants such as seaweed were dying. This pungent gas is what gives ocean air "sort of a fishy, tangy smell," said study author Andrew Johnston of the University of East Anglia."


Reef tanks can also release hydrogen sulfide (H2S; the rotten egg smell of decay) to the air:

Hydrogen Sulfide and the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com
http://reefkeeping.com/issues/2005-12/rhf/index.php

B. Iodine. There are many inorganic (I2, HOI) and organic iodine compounds (e.g., methyl iodide, CH3I) that can be released to the air from a reef tank. These compounds are important on a global scale for ozone depletion.

https://www.nature.com/articles/srep26007

"Iodine plays an important role on atmospheric chemistry by destroying tropospheric ozone and forming new particles1,2,3, especially in the marine boundary layer."

"CH3I is usually considered to be derived from oceans13. Emission from photochemical reactions in the surface sea water is the dominant source of CH3I. Biogenic activity of phytoplankton and macroalgae is also its important source, especially in coastal regions. "

D. Chlorine

Whole most chlorine in a reef tank is present as chloride (Cl-), which will not enter the air, there are organic and inorganic forms that will, just as there are for iodine.

Ocean-atmosphere exchange of methyl chloride: Results from NW Atlantic and Pacific Ocean studies
http://onlinelibrary.wiley.com/doi/10.1029/96JC02915/abstract