Overview
ISO 172:1978 specifies a qualitative method for detecting the presence of free ammonia or other volatile bases in phenol‑formaldehyde mouldings (phenoplasts). The procedure detects alkaline vapours released from a powdered sample by exposing universal indicator paper to the vapour in a sealed flask. ISO 172:1978 is intended for use where the absence of free ammonia is a requirement for the finished moulding.
Key topics and requirements
- Scope: Qualitative detection of free ammonia or other volatile bases in phenol‑formaldehyde mouldings.
- Principle: Alkaline vapours from a powdered test portion change the colour of universal indicator paper when confined in a sealed vessel.
- Apparatus
- Means to reduce mouldings to powder (filing, milling, grinding, turning or drilling) - avoid undue heating.
- Balance accurate to 0.01 g.
- Glass‑stoppered flask, 50 ml capacity.
- Universal indicator test paper, pH range 1.0 to 11.0.
- Sample preparation
- Reduce a fully representative sample to powder promptly; test prepared sample without delay.
- Typical test portion: approximately 1 g.
- Procedure
- Place the powdered sample in the 50 ml stoppered flask, quickly stopper with a distilled‑water‑moistened strip of universal indicator paper positioned so it projects into the flask but does not contact the sample.
- After 30 minutes examine the indicator paper for colour change.
- Interpretation
- No colour change: report absence of free ammonia/volatile bases.
- Colour change: report presence of free ammonia or other volatile bases.
- Test report must include
- Reference to ISO 172:1978.
- Identification of the sample.
- Method used to reduce the moulding to powder.
- Presence or absence of free ammonia/volatile bases.
Applications and users
- Quality assurance and incoming/outgoing inspection for manufacturers of phenol‑formaldehyde mouldings (phenoplasts).
- Materials testing and QA/QC laboratories performing plastics testing.
- Product certification bodies and compliance checks where ammonia‑free mouldings are required for safety, odor control, or downstream processing.
- R&D groups verifying processing changes do not introduce volatile alkaline residues.
- Useful as a simple, low‑cost screening test to flag samples for further quantitative analysis (when necessary).
Limitations
- This is a qualitative test only - it indicates presence or absence of volatile bases but does not quantify concentration.
- A positive result indicates alkaline vapours but cannot distinguish between ammonia and other volatile bases without additional analysis.
Related standards
- ISO 172:1978 supersedes ISO Recommendation R 172‑1961 and was developed by ISO/TC 61 (Plastics). For quantitative analysis or broader plastics testing methods, consult applicable ISO plastics testing standards and laboratory procedures.