Boiler water tests (Alkalinity)

p- alkalinity test-(phenolphthalein alkalinity)(std value is 60ppm) 100ml of sample+ 1ml of phenolphthalein(sample turns pink+ titrate it 50N sulphuric acid . Ppm 0f caco3= 10* ml of acid. Theory- hydroxides and carbonates are more reactive than phenolphthalein, so it will only react with acid after other compounds getting neutralized. it shows full hydroxides and half of carbonates as carbonates react with acid to form bicarbonates which is less reactive than phenolphthalein. for finding bicarbonates, we have to do m-alkalinity or total alkalinity test: take sample left after p-alkalinity test and add 1 ml of methyl orange(sample turns yellow) and titrate it with 50 N sulphuric acid. sample turns pink. ppm of caco3= 10*ml of acid. if no colour change when methyl orange is added no carbonate in sample. Caustic alkalinity. measures only hydroxides, we add 10ml of barium chloride to precipitate all carbonates and titrate using phenolphthalein and acid.