In article ,
The Natural Philosopher writes:
I wasn't aware you could buy sulphamic in 'pure' form cheaply. If so,

DS-3 is pure, as in not mixed with sand or any of the other things
you find added to kettle descaler sachets to make the active ingredient
in the things fill more horribly over-priced packets.
However, it has a coloured dye and a smell added, so you don't mistake
it for something else. The dye is also an indicator, changing colour
when the acid is exhausted. I have noticed the dye stain plastic brush
bristles -- I guess there's a possibility of it staining some more
important plastics. It's not suitable for use on enamelled baths.

--
Andrew Gabriel