Chapter 22

Calculate the salinity of sea water (simply expressed as a \% (w/w) of NaCl in water) from the following experimental data: sea water \((10.00 \mathrm{~mL})\) was transferred to a tall beaker, and concentrated nitric acid \((0.5 \mathrm{~mL})\) and deionised water \((200 \mathrm{~mL})\) added. Silver nitrate solution (0.1 M) was added drop-wise from a burette with constant stirring until coagulation of the precipitate began to occur. The suspension was heated to boiling and stirred (5 min) and a few drops of silver nitrate solution added to confirm completeness of precipitation. The suspension was allowed to cool in the dark (30 min) and then filtered through a pre-weighed sintered crucible (porosity 4 ) using dilute solution of nitric acid [3 \(\mathrm{mL}\) of \(2 \mathrm{M}\) dissolved in deionised water \((300 \mathrm{~mL})]\) for transfer and washing. The precipitate and crucible were dried to constant weight to yield silver chloride \((0.8329 \mathrm{~g})\).