In the manufacture of paper, degumming of fibrous raw materials is commonly carried out using which chemical reagent?

Introduction / Context:
Degumming is an important pretreatment step in many industries that use plant based fibres, including the paper and pulp industry. Raw materials such as wood chips, bamboo or agricultural residues contain gums, resins and other non cellulose impurities that must be removed before high quality paper can be made. This question tests awareness of the common chemical used in degumming, which is closely related to basic ideas about alkalis and their ability to break down unwanted organic materials.

Given Data / Assumptions:
- The context is industrial manufacture of paper from fibrous raw materials.
- Degumming means removal of gummy and resinous substances from the raw fibre feedstock.
- Options include strong mineral acids, bleaching agents, an alkali and an inert filler.
- Typical textbook level description emphasises alkali treatment in pulping and degumming processes.

Concept / Approach:
Degumming and pulping of plant fibres often rely on alkaline conditions. Caustic soda, or sodium hydroxide, is a strong base that can saponify fats, resins and waxy substances and can also help break down pectins and other gums. This loosens and removes non fibrous components, leaving behind cellulose fibres suitable for paper making. Strong acids like sulphuric acid or nitric acid are more likely to cause excessive hydrolysis of cellulose, which would weaken the fibres rather than gently clean them, so they are not standard degumming reagents in this context.

Step-by-Step Solution:
Step 1: Recall that paper manufacture involves converting raw fibrous material into relatively pure cellulose fibres by removing gums, resins and lignin. Step 2: Note that industrial pulping and degumming frequently use alkaline solutions, especially sodium hydroxide, to break down and dissolve these unwanted components. Step 3: Evaluate sulphuric acid and nitric acid. These strong mineral acids can cause harsh hydrolysis of cellulose and are not typically used alone for controlled degumming of paper raw material. Step 4: Consider bleaching powder. It is mainly used for bleaching and disinfection rather than primary degumming, although it may appear later in the process for whitening pulp. Step 5: Recognise that caustic soda is the standard and widely cited chemical for alkali treatment and degumming of plant fibres, so it is the most appropriate answer.

Verification / Alternative check:
Textbook descriptions of paper manufacturing usually mention steps like chemical pulping using sodium hydroxide and sometimes sodium sulfide, as in the kraft process. These treatments operate under alkaline conditions to remove lignin and gums. In contrast, bleaching agents such as chlorine compounds or hydrogen peroxide are described in separate bleaching stages, not in the initial degumming step. Industrial safety considerations also favour controlled alkali use over strong mineral acids in large scale fibre processing. These observations support caustic soda as the correct reagent for degumming.

Why Other Options Are Wrong:
Sulphuric acid and nitric acid are powerful acids that would damage cellulose fibres if used aggressively and are therefore not standard degumming agents in paper production. Bleaching powder is used primarily for bleaching and disinfection rather than for dissolving gums and resins from raw fibres. Calcium carbonate is a filler added to finished paper to improve brightness and opacity, not a degumming chemical. Only caustic soda matches the typical role of an alkaline degumming and pulping agent.

Common Pitfalls:
Learners sometimes assume that any strong chemical, including powerful acids or bleaching agents, can clean raw materials equally well. This leads to confusion between degumming, pulping and bleaching stages. Another pitfall is forgetting that cellulose must be preserved while impurities are removed, which means the reagent must be strong enough to dissolve gums yet gentle enough to avoid destroying the fibre structure. Remembering that alkalis, especially sodium hydroxide, are central to pulping and degumming helps avoid these errors.

Final Answer:
In paper manufacture, degumming of fibrous raw materials is commonly carried out using Caustic soda (sodium hydroxide, NaOH).