One reason it is harder to find is because it can be used in the formulation of illegal drugs and explosive devices. It was also used to treat fungal problems in fish aquariums. Back in my childhood ( I won't say how far back) it was a standard chemical in a chemistry set. Caution should be taken when used. It still can be obtained from chemical suppliers, but unfortunately in large quantities.<br><br>Thanks<br>Ted Fisher EMT I/D<br><br>