It is as the title says, is there any good agent for binding to chlorine in blood, for fauna that respirate such a thing. Like iron bonds to oxygen in our own blood, in order to transport it?

I tried doing research but couldn't find good information on what would be a suitable replacement for iron. Or if maybe iron itself would work. I can't find much information at all on how biochemistry would work for Chlorine-based respiration. And what I can find does not touch on this.

I am open to radically different biochemistry, as I already have made radical changes to biochemistry as necessary for this to work. So it does not need to be Earth-like.

  • $\begingroup$ Iron and a bunch of other metals love forming compounds with chlorine. No idea how to go from that fact to speculative biochemistry, though. $\endgroup$
    – g s
    Commented May 26 at 7:57
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    $\begingroup$ The difficult thing about a chlorine-transport molecule would not be picking up the chlorine, it's extremely reactive. The difficult thing would be convincing it to part with the chlorine when it got where it was going. $\endgroup$
    – Cadence
    Commented May 26 at 8:14
  • $\begingroup$ I think you need to clarify this. It looks to me like you're asking for a way to make critters that respire a chlorine-gas atmosphere, but also have an Earth-like biology. $\endgroup$
    – fectin
    Commented May 27 at 13:29
  • $\begingroup$ @fectine I meant just breath chlorine in general, they don't have to be extremely Earth-like. $\endgroup$ Commented May 27 at 19:44
  • $\begingroup$ To be clear, I already made various changes to their biochemistry that distance them from Earth-like Life. $\endgroup$ Commented May 27 at 19:47

4 Answers 4


Chlorine is hyper reactive- so literally everything is a binding agent. Proteins. Fats. It clumps up and is dead matter. If you had that in blood, you need a entirely different chemistry to build the body. Something that is mostly inert to the "energy" carrier- porcelain, certain plastics, crystals and very stable pure carbon configurations.

Then you have the cells who use the power source from the "blood". They need a way to use the energy released by chemical annihilation of the acid. Ideal would be a 2nd base producing system, resulting in heat on combination and pH-neutrality. If there is some insane micro turbine spinning, you can produce something that is half-way familiar. A https://en.wikipedia.org/wiki/Mitochondrion like structure, that can drive the rest of the cells.

The problem is that such a system is highly unstable and prone to self-destruction. Inner bleedings equals a continuous self-denaturation. I have no idea how you would implement clogging and binding tissue generation with chlorine as energy carrier. The whole of the alien movies chemistry is bad and the xenomorphs should feel bad.

  • $\begingroup$ So what you are saying it I should make the blood flow through a heated structure that contains a secondary base for reaction? If I understand you correctly? $\endgroup$ Commented May 27 at 19:49

Binding Chlorine isn't an issue, binding it within a carbon-chain chemistry and having it A. unbind later and B. not totally wreck the carbon-chain molecules it interacts with on the other hand definitely is. This is not biology as we know it.

You can probably build something in allotropic carbon that can transport Cl2 as a metabolic agent. Many of these structures are relatively easy, in energetic terms, to open and close with specialised enzymes but relatively inert when it comes to reactions with simpler chemicals. This can make them ideal carriers for molecules that would otherwise destroy containment materials. As materials so transported are physically contained within the open space at the core of a carbon "cage" rather than being chemically bound issues with unbinding it and the potential damage to traditional water/carbon biochemistry presented by Chlorine are avoided, at this step in the metabolic chain at least.

This still leaves issues around the rest of the biology that tries to make use of Chlorine in a metabolic role but does give you some potential avenues for transporting it around the body.

  • $\begingroup$ They are carbon-based, but are not water-based. Would non-water based biochemistry get around some of these issues? If so, what solvents would be most effective at working with chlorine? $\endgroup$ Commented May 27 at 19:47
  • $\begingroup$ @DanceroftheStars Off the top of my head I'd have to go with a non-polar organic solvent so that Chlorine isn't destructively reactive, however anything inert enough to carry Chlorine without it reacting to it is going to be a poor solvent for other elements and compounds you need to have in a traditional biochemistry as well. I think this is a design new biochemistry from the ground up situation. $\endgroup$
    – Ash
    Commented May 28 at 4:34
  • $\begingroup$ grimace Guess I have to either get rid of this idea. Or use the best science of all, Handwavium. $\endgroup$ Commented May 28 at 20:59


Hemoglobin already has allosteric binding sites for chlorine. Some exotic variant could certainly bind and hold chlorine for use in cells.


Hemoglobin in the blood can bind to chlorine, forming compounds like chlorohemoglobin. This is one possible binding agent for chlorine in the bloodstream.

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    Commented May 28 at 2:37

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