Received from Matheus Costa via groups.io at 6/12/2020 15:16 UTC:
There are another method that don't use calcium hypophosphite. It's in this site (in portuguese, but google translate can be effective to get the essential):
Anyway, in that site there are a homebrew solution to manufacture calcium hypophosphite too.
Best regards
Matheus
The method at this site starts with Sodium Hypophosphite, which is as much a controlled substance as Calcium Hypophosphite.
Jim H
