[cbjessee]

Biochemist here - weak on inorganic and need some help.

In making alkaline peroxide for unharing of pigskins (keratin disruption in the leather industry), one combines NaOH and H2O2. In my case, I'm mixing 10M NaOH, Water and 30% H2O2 to a final solution of 5.2M NaOH and 3.75% H2O2. I observe mild heating on adding the NaOH to Water, and much more heat release upon adding the smaller volume of H2O2, with flash crystallization occurring within 5-8 seconds after H2O2 addition and rapid mixing. The crystals occupy the total solution space but settle upon disruption by stirring to about 1/3 solution volume.

The crystals enter solution at ~40C but drop back out at ~30C.

What crystals are forming and why?

[cbjessee]

Just a little more information:

4% H2O2 in 0.1M NaOH causes no crystallization, but 0.75% H2O2 in 1M NaOH does, albeit more slowly.

[cbjessee]

Some suggestion that this might be hydrated sodium peroxide, but I'm not sure how that could form.

Does this trigger any thoughts?

[Borek]

hydrated sodium peroxide

Doesn't sound like something stable enough.

[cth]

My guess is that you made the compound: Na₂O₂.8H₂O

It has been published nearly 15 years ago:
M. Grehl, R. Froehlich, S. Thiele, Acta Crystallographica, Section C: Crystal Structure Communications  1995,  C51(6),  1038-40