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1. $Ag^+$ (Silver nitrate) |
$Cl^-$ $+$ $Ag^+$ $\longrightarrow$ $AgCl$ - White, cheesy precipitate - Sensitive to light - Insoluble in $HNO_3$ Three essential modes of complex formation: $AgCl+2CN^-\rightarrow [Ag(CN)_2]^-+Cl^-$ (->dicyanoargentate) $AgCl+2NH_3\rightarrow [Ag(NH_3)_2]^++Cl^-$ (->diamminesilver) $AgCl+2S_2O_3^{2-}\rightarrow [Ag(S_2O_3)_2]^{3-}+Cl^-$ (->bis(thiosulfato)argentate) Research of chloride ions must be made by $AgNO3$ in the presence of $HNO_3 $! Indeed, in a neutral solution, the reagent also provides precipitation with the following anions: sulfite, carbonate, borate, thiocyanate, phosphate (yellow pr.!), acetate, oxalate, tartrate. All these precipitates (except $AgSCN$ ) are soluble in $HNO_3$ |
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2. $Pb^{2+}$ (Lead nitrate) |
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$2Cl-+Pb^{2+}$ $\rightarrow $ $PbCl_2$ - White crystalline precipitate - Soluble under heat - Diffic. complexed by HCl 1,19: $PbCl_2+2Cl^-$ $\rightarrow $ $PbCl_4^{2-}$ (-> tetrachloroplumbate(II)) |
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3. $Hg_2^{2+}$ (Hg(I)) nitrate |
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$2Cl-+Hg_2^{2+}$ $\rightarrow $ $Hg_2Cl_2$ - White precipitate (calomel) - Blackened by ammonia - Soluble in $HNO_3-HCl$ |