Chloride estimation by Mohr's method is a direct precipitation titration in which standard silver nitrate (AgNO3, N/100) reacts with chloride ions to form white silver chloride precipitate. The end point is signalled by the appearance of the first permanent brick-red precipitate of silver chromate (Ag2CrO4) formed from the chromate indicator (K2CrO4, 5%) when all chloride has been consumed. A blank titration on distilled water corrects for the indicator error — the small volume of AgNO3 required to produce the visible Ag2CrO4 end point colour in the absence of any chloride. The experiment explains the chemistry of why the red precipitate initially forms and re-dissolves during the titration, and why the method requires the sample pH to be maintained between 7 and 8. Results are expressed in g/L and converted to ppm (mg/L) and compared against the WHO palatability guideline of 250 ppm. The engineering significance of chloride in boiler water is explored: MgCl2 hydrolyses under boiler conditions to generate HCl, causing severe acid pitting corrosion of boiler tubes and drums. Mandatory handling and waste disposal procedures for AgNO3 are prescribed.