Titration analysis method-acid-base titration method (3)

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

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