Nothing in my Dangerous Good Handbook and I cannot find anything definitive on-line either. I’m going to suggest that because it’s packed in 25kg bags inside the totes it will be exempt; but I’d rather wait for Dave’s verdict to be certain.
I’ll be interested in the result because it’s the sort of stuff I may well be carrying in the future, it’s used a lot in animal feeds. Yes I know it’s nasty stuff to use to clear drains, but apparently it converts when mixed with moist wheat to sodium bicarbonate like the missus has in the kitchen cupboard.