Overview
ISO 697:1981 specifies a standardized laboratory method for determining the apparent density (bulk density) of washing powders and similar powdered surfactants by measuring the mass that fills a known volume. The method produces a conventional, reproducible value for quality control and material specification. It applies to free‑flowing powders and, with an appropriate funnel, to powders that tend to cake. Powders with lumps may be tested only if lumps can be readily disintegrated without breaking particles.
Key topics and technical requirements
- Apparatus
- Funnel with smooth, non‑electrifying surfaces; orifice 40 mm for free‑flowing powders or 60 mm for caking powders.
- Receiver of nominal 500 ml capacity (calibrated and adjustable to 500 ± 0.5 ml).
- Stand to hold funnel and receiver in fixed alignment, closure plate (110 × 70 mm), straightedge (~150 mm) and a glass plate (100 × 100 × 7 mm).
- Receiver calibration
- Calibrate by weighing the empty receiver, filling with recently boiled distilled water at 20 °C (using the glass plate to set the volume), and weighing again to establish the receiver volume.
- Test procedure
- Fill funnel with test sample, quickly remove closure plate so powder fills and overflows into calibrated receiver.
- Level the surface with a straightedge, clean exterior, and weigh receiver + sample to 0.1 g accuracy.
- Perform at least two determinations on different portions of the laboratory sample.
- Calculation and reporting
- Apparent density = (mass of powder in receiver) ÷ (calibrated receiver volume) → expressed as g/ml, reported to three significant figures.
- Repeatability: the two successive results by the same analyst must not differ by more than 5% of the mean.
- Test report should record sample ID, presence of lumps, funnel orifice used (40 or 60 mm), results and any deviations.
Practical applications and users
- Quality control laboratories in detergent and surfactant manufacturing for batch release and specification checks.
- Product development and formulation teams assessing flowability, dosing performance and packing behavior of washing powders.
- Packaging engineers and logistics planners estimating bulk handling, storage volume and transport weight.
- Independent test labs, standards bodies and regulatory agencies requiring reproducible bulk density data for compliance and comparison.
Related standards
- ISO 607 - Surface active agents and detergents: methods of sample division (sampling and sample preparation referenced by ISO 697).
- ISO 3424 - Determination of bulk density for related powdered materials (apparatus and technique overlap).
Keywords: ISO 697, apparent density, bulk density, washing powders, surfactants, measurement method, funnel orifice, receiver calibration, detergent quality control.