Shipping paraformaldehyde legally isn't easy.
I used to fly with it (add water to get formalin solution for preserving specimens. Carrying paraformaldehyde is much less problematic than carrying formalin and beats shopping for formalin in country. In some countries, e.g., Paraguay, formalin is a controlled substance, one needs a prescription to buy it.). Stopped after I had visions of a customs officer finding my white powder and tasting or sniffing it.
Old friend, now dead, once flew with a Nalgene bottle of formalin in a soft-sided suitcase. The airline's baggage smashers broke the bottle while loading checked bags. Flight cancelled, bomb scare, bomb-sniffing dogs rendered nose-dead, many many unpleasant repercussions.