Spaw, your reference to salting peters (while amusing, and provoking thought on the phrase "banging on") only makes sense in the version of English domiciled between the Atlantic and Pacific Oceans. Everywhere else saltpetre is the common name of the chemical in English.

Cheers, Rowan
from Australia, where the legislation has just been implemented that requires special controls on such chemicals but allows looser controls on quantities up to 3kg. Thankfully I don't have a swimming pool and thus don't have to even think about "pool chlorine", also a red hot oxidising agent sold in bulk.