The invention consists of a moisture indicator and a process
of indicating moisture content of ambients by the use of
cobalt-substituted sulfonated strong acid cation exchangers
and particularly those polymers of the polyvinyl aryl type such as disclosed in US. Pat. No. 2,366,007 granted Dec. 26, 1944.
Typical is the sulfonated polystyrene divinylbenzene
copolymer, the same being used in loose or in bonded form.