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3.
(1) Alkalinity composition
For example, a large number of algae thrive in natural water bodies, which strongly absorb CO 2 in the water, so that the water has a higher pH value, mainly carbonate alkalinity.
(2) Determination of alkalinity
Determination of alkalinity available continuous titration: taking up a volume of water sample, phenolphthalein indicator was added standard solution was titrated to a strong acid, to the solution from red to colorless, the amount of the standard solution of the acid represented by P
Phenolphthalein discoloration:
Methyl orange discoloration:
The total alkalinity of water: T = OH - + CO.
The relationship between various alkalinity and acid-base titration results is shown in Table 2.
Table 2.
(3) Alkalinity calculation
1) First judge the composition of alkalinity by the values of P and M (see Table 2.
For example, the result of the titration is P=11.
The total alkalinity is P+M=19.
2) The expression method of alkalinity
3) Commonly used molar mass for alkalinity calculation
4) Expression for alkalinity calculation
.
[Example 2.
2.
1] The titration result of continuous titration is P=11.
05ml, M=8.
90ml; known V water sample=100ml, CHCl=0.
1mol/L
.
After analysis, the alkalinity components in the water are OH - and CO 3 2- , the content of OH- is PM =2.
15ml, the content of CO 3 2- is 2M=17.
80ml, and the total alkalinity is P+M=19.
95ml
.
The result of alkalinity calculation can be expressed as
Related links: Titration analysis method-acid-base titration (2)