(2), 0. 1% methyl orange indicator. Methyl red-methylene blue indicator. (3) Standard sulfuric acid solution (c = 0.1000 mol/l \ 0.0100 mol/l). (2) Determination method:

1, water samples with high alkalinity, such as boiler water and other water (mmol/l) (1), take 100ml boiler water sample and inject it into a 250ml conical flask.

(The temperature of boiler water sample should be between 20 ~ 250℃)

(2) Add 2-3 drops 1% phenolphthalein indicator. If it is red, use 0. 1mol/l sulfuric acid standard.

Titrate the solution until it is colorless, and record the acid consumption (V 1). Add 2 drops of methyl orange indicator, titrate with sulfuric acid standard solution until the solution is orange red, and record the acid consumption (V2).

2. For water samples with low alkalinity, such as condensed water and backwater (mmol/l) (1), take 100ml transparent water sample and inject it into a 250ml conical flask.

(2) Add 2-3 drops 1% phenolphthalein indicator. If it is red, titrate it with 0.0 1mol/l sulfuric acid standard solution with a micro burette until it is colorless, and record the acid consumption (V 1). Add 2 drops of methyl orange (red)-methylene blue indicator, titrate with sulfuric acid standard solution until the solution is orange red, and record the acid consumption (V2).

(3) Calculation method (Note: the alkalinity of methyl orange is the total alkalinity, that is, the final alkalinity). Phenolphthalein alkalinity (JD) Phenol = C * V 1 * 10 ................. mmol/L (1).

Alkalinity of methyl orange (JD) = C * V2 * 10 ................... mmol/l (2)

Where: c refers to the molar concentration of sulfuric acid standard solution, mol/L;

V 1, v2-volume of consumed standard sulfuric acid solution, ml; (V2 does not contain V 1)