Pulp alkali solubility refers to the degree of solubility of soluble cellulose in pulp under certain alkaline conditions, usually expressed by the solubility of alpha cellulose (α-cellulose). The following is a commonly used measurement method:
Sample preparation: Add 1 gram of pulp sample into a test tube containing 5% sodium hydroxide (NaOH), stir well, and then dilute to 100ml with water.
Filtration: Filter the solution and keep the filtrate.
Titration: Take 25ml of filtrate, adjust its acidity with hydrochloric acid (HCl), and then titrate with sodium hydroxide solution until the color of the test solution turns light yellow. During the titration, methyl red indicator needs to be added.
Calculation: Calculate the alkali solubility of pulp according to the volume of sodium hydroxide solution consumed by titration and the quality of the sample. The calculation formula of alkali solubility is: alkali solubility (%)=(V1-V2)×N×1000/W, where V1 represents the volume of titration solution, V2 represents the volume of titration solution in blank test, and N represents the concentration of sodium hydroxide solution , W represents the mass of the sample.
North and South Chao reminds you: This method measures the alkali solubility of alpha cellulose, not the solubility of the whole cellulose. Therefore, when using this method to determine the alkali solubility of pulp, certain corrections are required.
