Why are strong oxidizing agents "incompatible" with ferrocyanide according to SDS?

As I've mentioned in [this question](https://chemistry.stackexchange.com/questions/162420/synthesis-of-sodium-ferricyanide), I am making $\ce{Na3Fe(CN)6}$ from $\ce{Na4Fe(CN)6}$ by oxidizing the ferrocyanide using sodium permanganate. The [SDS](https://www.fishersci.com/store/msds?partNumber=AC459290010&productDescription=SODIUM%20FERROCYANIDE%20DECA%201KG&vendorId=VN00032119&countryCode=US&language=en) of sodium ferrocyanide as well as potassium ferrocyanide mention that they are "incompatible" with strong oxidizing agents. What reaction can occur that causes them to be incompatible? Can the reaction with strong oxidizing agents release $\ce{HCN}$, as is the case with strong acids and ferrocyanide?




The earlier answers' and comments line of thought gravitates around «what may happen *to* $\ce{Na3Fe(CN)6}$ or/and $\ce{Na4Fe(CN)6}$ in the presence of strong oxidizers» to the effect that MSDS express a warning.


*Complementary* to this, I suggest one should keep an eye *on the oxidizer*; because if there is an oxidation *by them*, simultaneously, they are going to be reduced. Hydrogen peroxide is an example of a strong oxidizer commercially available (many chemistry labs have a bottle of 30% solution in stock [e.g., to prepare [piranha solution](https://en.wikipedia.org/wiki/Piranha_solution)]). Thus, a search with the three keywords «H2O2», «decomposition», and «Na4Fe(CN)6» yields for example the following entry in [semantic scholar](https://www.semanticscholar.org/paper/Effect-of-pH-on-the-Rate-of-H2O2-Decomposition-over-Zrn%C4%8Devi%C4%87-Pajc/0a494430e6dd634dfe352d7db2f03b10d2811a6a):



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> Corpus ID: 101692556
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> Effect of pH on the Rate of H2O2 Decomposition over K3Fe(CN)6 Catalyst
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> S. Zrnčević, Emil Pajc, V. Markov | Published 1973 | Chemistry
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> Pracena je brzina raspada vodikovog peroksida uz katalizator K3Fe(CN)6 u intervalu pH vrijednosti od 9 do 13 pri 30 0C. U navedenom intervalu pH u odsutnosti katalizatora dobivena je linearna ovisnost konstante brzoine reakcije o pH, a uz dodatak katalizatora u istom pH podrucju nađeni su maksimumi bruzina reakcije. Diskutira se reakcijski mehanizam u prisutnosti katalizatora.
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which basically is a copy of an entry at [CROSBI](https://www.bib.irb.hr/295861), the Croatian scientific bibliography. From [Google translate](https://translate.google.hr/?sl=hr&tl=en&text=Pra%C4%87ena%20je%20brzina%20raspada%20vodikovog%20peroksida%20uz%20katalizator%20K3Fe(CN)6%20u%20intervalu%20pH%20vrijednosti%20od%209%20do%2013%20pri%2030%200C.%20U%20navedenom%20intervalu%20pH%20u%20odsutnosti%20katalizatora%20dobivena%20je%20linearna%20ovisnost%20konstante%20brzoine%20reakcije%20o%20pH%2C%20a%20uz%20dodatak%20katalizatora%20u%20istom%20pH%20podru%C4%8Dju%20na%C4%91eni%20su%20maksimumi%20bruzina%20reakcije.%20Diskutira%20se%20reakcijski%20mehanizam%20u%20prisutnosti%20katalizatora.%20&op=translate) of the abstract (*Sažetak*), the authors report a linear increase of the rate of decomposition of $\ce{H2O2}$ in the range of $\mathrm{pH}\ 8\dots 13$ at $\pu{30 ^\circ{}C}$. The presence of $\ce{K3Fe(CN)6}$ accelerates this even further.


Since the decomposition of $\ce{H2O2}$ into water and oxygen is exothermic ($\pu{–2884.5 kJ/kg}$, [reference](https://en.wikipedia.org/wiki/Hydrogen_peroxide#Decomposition)), the catalyst promoting a higher rate of reaction thus may lead into a runaway. By analogy, *I speculate* if $\ce{K3Fe(CN)6}$ (the publication) acts as a catalyst here, $\ce{Na3Fe(CN)6}$ (as in the original question) equally does so, too.


Reference:


Zrnčević, S.; Pajc, E.; Vasić, Đ.; Markov, V. Ovisnost brzine raspada $\ce{H2O2}$ uz katalizator $\ce{K3Fe(CN)6}$ o pH. *Kemija u industriji : časopis kemičara i tehnologa Hrvatske* **1973**, *1*, 21-24.


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Ferrocyanide $\ce{[Fe^{II}{CN}6]^{4-}}$ contains iron at the oxidation number $\pu{II}$. It can easily be oxidized to the ferricyanide ion $\ce{[Fe^{III}(CN)6]^{3-}}$containing iron at the oxidation number $\pu{III}$. This oxidation can be done by strong oxidants like elemental chlorine $\ce{Cl2}$ according to $$\ce{[Fe^{II}(CN)6]^{4-} + Cl2 -> [Fe^{III}(CN)6]^{3-} + 2 Cl-}$$


According to Cotton and Wilkinson, ferrocyanides are extremely stable and not decomposed into cyanides and $\ce{HCN}$ by acids at ordinary temperatures. So their solutions are not poisonous. High temperatures and concentrated acids are required to carry out this decomposition. Surprisingly enough, ferricyanides are quite poisonous : they have a greater tendency to be labile and to loose one $\ce{CN-}$ ion, for kinetic reasons, according to these authors. Their reaction in water is slow but proceeds according to $$\ce{[Fe^{III}(CN)6]^{3-} + H2O -> [Fe^{III}(CN)5(H2O)]^{2-} + CN^-}$$


See : F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, Interscience Pub., Wiley & Sons, 1972, p. 865.


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Cyanide can be oxidized to cyanogen [(CN)2] cyanate and eventually to CO2 and nitrogen. In solution ferro and ferricyanides are relatively stable and do not readily release cyanide ion so ferricyanide is resistant to further oxidation. I would think that a mix of solid ferricyanide and a solid oxidant or high concentration of oxidant such as 35% peroxide could potentially react violently if initiated.


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In my opinion, the statement is because the reaction between ferrocyanide and permanganate may be intense enough to cause dangers, like splattering.
I can't seem to find any info regarding HCN generation, and it is likely not due to that because even if the gas is formed, it will be oxidized to nitrogen or cyanate by the permanganate.
Also, many other quite unreactive chemicals are "incompatible" with strong oxidizing agents according to their SDS, including [sodium phosphate](https://www.fishersci.com/store/msds?partNumber=S37512&productDescription=&vendorId=VN00033897&keyword=true&countryCode=US&language=en) and [silicon dioxide](https://www.fishersci.com/store/msds?partNumber=AC437150050&productDescription=&vendorId=VN00032119&keyword=true&countryCode=US&language=en).


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