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Hydrogen peroxide (H2O2) from the local shop (dilute, 2-3%) sometimes has a stabilizer to slow its breakdown rate and increase its "shelf-life", since we'd like to keep it around the house on our shelf for years, and the shop would like the option to keep it on their shelf for a while as well.

Examples of H2O2 stabilizers include acetanilide and sodium citrate.

This answer notes that the Soyuz spacecraft (the one with the now-patched hole) also has a "shelf-life" and this one is only about 200 days, for reasons explained there.

Is it known if the Soyuz spacecraft(s) docked to the ISS use chemical stabilizers in its H2O2 so that it can remain docked to the ISS for 200+ days?

(Note that the Soyuz's H2O2 is at a much higher concentration [82%] than what you can buy at your grocery store.)

More info about the situation:

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    $\begingroup$ Interesting question. My ignorance of chemistry is vast, but it would seem that the stabilizers would work by decreasing the reactivity of the fuel, so may be undesirable. $\endgroup$ – Organic Marble Oct 14 '18 at 16:53
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    $\begingroup$ @Uwe absolutely not. This question is specific to spaceflight and not about chemistry. I just asked if chemical stabilization is used or not. I did not ask how it works. I think the questions you raise are quite interesting and I hope you ask them as a follow-up! $\endgroup$ – uhoh Oct 15 '18 at 0:07
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    $\begingroup$ @OrganicMarble unchecked H2O2 degradation is likewise undesirable, thus the question. There is exposure to temperature extremes which could accelerate degradation to worry about for example. $\endgroup$ – uhoh Oct 15 '18 at 0:09
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    $\begingroup$ very slightly related How long could the shuttle remain docked to ISS and still capable of landing? $\endgroup$ – uhoh Oct 15 '18 at 22:32
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    $\begingroup$ The problem might be not only the instability of hydrogen peroxide. H2O2 is very corrosive and incompatible to many construction materials. Even electrolytic corrosion is possible when different metals are used in contact with hydrogen peroxide. See this NASA report of experiences with the X-15. $\endgroup$ – Uwe Oct 17 '18 at 14:51
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According to international chemical supplier Evonik:

"...rockets require especially pure hydrogen peroxide, because any impurities would deactivate the catalyst. ... 'Evonik has decades of experience in manufacturing hydrogen peroxide using a process it developed itself and we have the technical ability to concentrate this aqueous solution up to 98 percent,' says [Dr. Stefan] Leininger. It is precisely such high concentrations of hydrogen peroxide that are needed to power space rockets. "

AFAIK, there is no way to 'shelf-stabilize' propellant-grade H2O2; it is desirable as a hypergolic monopropellant fuel because it spontaneously decomposes when heated or run over a catalyst, like Manganese (II) Dioxide or Potassium Chloride. That's why their 'operational limit' is set at 200 days; to avoid RCS problems upon separation and reentry. The peroxide in the Soyuz RCS system is over 90% concentrated; as such it is a toxic, caustic oxidizer, and that is why it is stored outside the crew capsule.

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    $\begingroup$ This is an interesting answer to read, and could very well be correct! Can you add some kind of supporting links to some of the information here? Good Stack Exchange answers are not generally of the AFAIK or to my knowledge variety. SE runs a bit different than other Q&A sites and answers should rely upon verifiable information rather than personal knowledge. Thanks! $\endgroup$ – uhoh Dec 3 '18 at 4:25
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    $\begingroup$ Evonik, as of this answer, appears to be the current supplier of propellant-grade H2O2 to Roscomos; so I think I finally 'hit the nail on the head.' $\endgroup$ – Hunting.Targ Dec 16 '18 at 19:40
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    $\begingroup$ The nail's head has indeed been hit. Thanks! $\endgroup$ – uhoh Dec 16 '18 at 19:47
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    $\begingroup$ Wow, 100+100=200! What is the association bonus? I've never seen that happen like that before. $\endgroup$ – uhoh Dec 18 '18 at 14:02
  • $\begingroup$ Wikipedia gives the concentration of the Soyuz's hydrogen peroxide as 82%, rather than 90+% (no source provided, however). $\endgroup$ – Sean Dec 4 '19 at 23:51

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