... give a child a child-safe chemistry set if the child next door has also been given a child-safe chemistry set, but not the same make and model of the first child's child-safe chemistry set (are you following this?) because just because one manufacturer's set of chemicals is safe within itself, it doesn't necessarily follow that the two together are.

On a similar note point out to said children ...

Never think that an aerosol can of room freshener can be used in lieu of fire extinguisher if, by combining more than one chemistry set, your mother's basement curtains catch on fire.

I've always thought there might be a ballad in there somewhere - something along the lines of The Sicknote ...

siân