Overview
ISO 4119:1995 - "Pulps - Determination of stock concentration" specifies a laboratory method for measuring the stock concentration (dry-matter content) of aqueous pulp suspensions. This second edition replaces ISO 4119:1978 and is intended as a reference procedure used before other pulp tests and within a range of ISO standards that handle pulp suspensions. The method is in principle applicable to all kinds of aqueous pulp suspensions but is not intended for determining the saleable mass of slush pulps.
Key topics and requirements
- Purpose: Determine pulp concentration expressed as percentage by mass [ % (dm) ].
- Scope: Applicable to all aqueous pulp suspensions; excludes saleable mass determination for slush pulps.
- Sampling:
- Mix suspension thoroughly and keep agitated during sampling to avoid fiber separation.
- Typical working sample ≈ 500 g; for low concentrations (≤ 0.3 % dm) collect enough to yield ~1–5 g dry mass.
- Filtration:
- Use a filtration device (e.g., Büchner funnel 90–150 mm) with circular filter paper that retains all visible fibers.
- Apply vacuum, rinse vessel walls, check filtrate for visible fibers; repeat filtration or change to less porous paper if fibers pass.
- Drying and weighing:
- Dry filter + fiber cake to constant mass. Oven temperature: 105 °C ± 2 °C; hotplate: 150 °C ± 15 °C.
- Microwave drying allowed only when empirically shown to match oven drying; warn against carbonization.
- Balances: sample balance able to weigh 100–500 g with error <0.1 %; balance for dried cake with error <0.1 %.
- Dilution and aliquots:
- For concentrations > 1 % dm dilute to below 1 % before taking aliquot; document dilution mass precisely.
- Calculation and reporting:
- Calculate concentration X using masses of initial sample, added water (if diluted), aliquot, filter paper and dried fiber cake.
- Report average of determinations with two decimal places and include test details, sample identification and any operational deviations.
Applications and users
ISO 4119 is practical for:
- Laboratory technicians performing routine pulp testing and quality control in pulp and paper mills
- R&D and process laboratories establishing pulp properties prior to further analyses (freeness, viscosity, chemical content)
- QA/QC teams verifying stock concentration for process control and consistency
- Standards committees and testing labs that reference a harmonized pulp stock concentration determination method
Keywords: ISO 4119, pulp concentration, stock concentration, pulp suspensions, laboratory method, pulp testing, pulp stock concentration determination.
Related standards
- Developed by ISO/TC 6 (Papers, board and pulps), subcommittee SC 5 (test methods and quality specifications).
- ISO 4119 is referenced by other ISO test standards dealing with pulp suspensions and serves as a preparatory, harmonized method for subsequent pulp analyses.
