ENVE 201 Environmental Engineering Chemistry 1 . CHLORIDES (Chapter 21) Dr. Aslıhan Kerç. Chlorides. As mineral content ↗ Cl - ↗ Upland, Mountain supplies low in Cl - High in rivers and groundwater Sea-Ocean ↗. Sources of Chloride. Surface waters dissolve chlorides from top soil.
Dr. Aslıhan Kerç
As mineral content ↗ Cl- ↗
There is a hydrostatic balance between seawater and groundwater in areas adjacent to the ocean. Over pumping of groundwater disturbs the balance.
Salt water intrusion into well
Evapotranspiration of water used for irrigation
Highly saline irrigation water return to the surface waters
Normal evaporation also increases salt content ofsurface water.
6 gr Cl- / person / day
Cl- and nitrogen determination used for detecting contamination of groundwater by wastewater
Cl- measurement and total salinity important for irrigation water
Chlorides can be used as tracers in Env. Eng. in groundwater studies.
Potassium chromate as the indicator
Mercuric nitrate titrant
Titration w/silver nitrate solution
Chloride present complexes with silver ions
When all chloride complexes silver ion concentration increases
Sudden increase in voltage
0.0141 N silver nitrate ( N / 71 )
Each ml = 0.5 mg Cl-
Cl- is precipated as silver chloride
Ag+ + Cl- AgCl (white precipitate)
End point presence of excess Ag+
2 Ag+ + CrO-24 Ag2CrO4 (reddish-brown ppt)
Cl- (mg/L) = ( ml AgNO3 – blank)*0.5 *1000
0.0141 * 35.45 =0.5