Using Mass as a Signal

What if the analyte is an aqueous ion, such as Pb + In this case we cannot isolate the analyte by filtration because the Pb + is dissolved in the solution s matrix. We can still measure the analyte s mass, however, by chemically converting it to a solid form. If we suspend a pair of Pt electrodes in our solution and apply a sufficiently positive potential between them for a long enough time, we can force the reaction 

If HgCh is added in excess, each mole of produces one mole of Hg2Cl2. The 

Summarizing, we can determine an analyte gravimetrically by directly determining its mass, or the mass of a compound containing the analyte. Alternatively, we can determine an analyte indirectly by measuring a change in mass due to its loss, or the mass of a compound formed as the result of a reaction involving the analyte. 

A gravimetric method in which the signal is the mass of a precipitate. 

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