Pulp, paper and paperboard - Determination of calcium content

Calcium content in pulp, paper and board can be determined by standard titration as follows:

1. Take a certain amount of pulp, paper or cardboard sample and add a certain amount of acetic acid to convert the calcium ions in the sample into calcium acetate precipitates.

2. The sample was mixed with acetic acid solution, and sodium acetate indicator was added to make the solution red.

3. Titrate with 0.05 M EDTA solution until the solution turns blue, record the volume V1 of EDTA used.

4. In the same way, titrate the blank sample and record the volume V0 of EDTA used.

5. Calculate the calcium content in the sample according to the following formula:

Calcium content (%) = [(V1-V0)×C×1000]/m

Among them, V1 is the volume of EDTA used in the titration of the sample, V0 is the volume of EDTA used in the titration of the blank sample, C is the concentration of the EDTA solution, and m is the mass of the sample.

Note: Before titration, the EDTA solution needs to be calibrated. In addition, various factors that may introduce interference, such as carbonates in the air, should be strictly controlled during sample preparation and processing.