<P> 5 . Drying and Ignition: The purpose of drying (heating at about 120 - 150 oC in an oven) or ignition in a muffle furnace at temperatures ranging from 600 - 1200 oC is to get a material with exactly known chemical structure so that the amount of analyte can be accurately determined . </P> <P> 6 . Precipitation from Homogeneous Solution: In order to make Q minimum we can, in some situations, generate the precipitating agent in the precipitation medium rather than adding it . For example, in order to precipitate iron as the hydroxide, we dissolve urea in the sample . Heating of the solution generates hydroxide ions from the hydrolysis of urea . Hydroxide ions are generated at all points in solution and thus there are no sites of concentration . We can also adjust the rate of urea hydrolysis and thus control the hydroxide generation rate . This type of procedure can be very advantageous in case of colloidal precipitates . </P> <P> As expected from previous information, diverse ions have a screening effect on dissociated ions which leads to extra dissociation . Solubility will show a clear increase in presence of diverse ions as the solubility product will increase . Look at the following example: </P> <P> Find the solubility of AgCl (K = 1.0 x 10) in 0.1 M NaNO . The activity coefficients for silver and chloride are 0.75 and 0.76, respectively . </P>

Precipitating agent suitable for the analysis of chloride