I have been mainly targeting solubility to get a precipitate on one but not the other since the cation really influences the colour of the solution. But it seems to be a tedious process of blindly choosing complementary ions and checking their solubility. Isn't there some easier way of dichotomously coming to the appropriate ion?
I'm not allowed to use any instrumental techniques such as ion chromatography, just simple qualitative tests involving the use of cations or anions. I instantly thought of odour and pH but I've been restricted to manipulation of ions.
It mainly seems you have to be creative and pluck an ion out of thin air from a VAST knowledge of product solubility, colour, stability. Is there some logical rationale I could use?