Hemicellulose content

Alpha cellulose, the portion of cellulose insoluble in 17.5% sodium hydroxide, is determined by treating 3 g of pulp or holocellulose in a 250 ml porcelain beaker with 25 ml of 17.5% NaOH, swelling for 4 minutes, and pressing with a glass rod for 3 minutes. Another 25 ml of NaOH is added, mixed for 1 minute to form a paste, and left covered at 20°C for 35 minutes. Then, 100 ml of distilled water is added, and the mixture is filtered under suction with a sintered glass funnel, with the filtrate reapplied twice and washed with water until neutral. Subsequently, 100 ml of 10% acetic acid is added dropwise, followed by more water. Cellulose content is calculated as 100% minus the sum of hemicellulose, lignin, and ash. Holocellulose, the total carbohydrate fraction (cellulose and hemicellulose), is estimated per Wise et al. (1946).

By Allschoolabs · August 2, 2025 · 25 views

The term alpha cellulose describes that part of cellulose which does not dissolve in 17.5% sodium hydroxide solution. Alpha cellulose can be determined according to Zellcheming Merkblatt IV/29 A. About 3 g (exactly weighed) of the sample (either pulp or holocellulose obtained from the raw material) are put in a porcelain beaker (250 ml), then 25 ml of 17.5% NaOH are added and the sample is left to swell for 4 minutes (time was exactly measured from the last drop), and then pressed with a glass rod for 3 minutes. After pressing, another 25 ml of sodium hydroxide are added and mixed thoroughly till a homogeneous paste is obtained (mixing for about 1 minute). The beaker is then covered and left for 35 minutes at 20°C. 100 ml of distilled water are then added and the material is quickly filtered under suction using a sintered glass funnel. The filtrate is then poured on the paste twice before washing with distilled water. After washing with distilled water till neutrality 100 ml of 10% acetic acid are added dropwise followed by distilled water.

Cellulose

This is calculated as:

Cellulose = 100% – (Hemicellulose + lignin + Ash)

Holocellulose estimation

Holocellulose is the total carbohydrate fraction (cellulose and hemicellulose) of the raw material as was estimated according to Wise et al., 1946.