Regulation 3(1)
1. In the case of a sample (other than a sample of coating) containing any wax, oil or other similar matter, that wax, oil or matter shall first be removed using n-heptane.
2. A sample of the coating or substance, as the case may be, shall be so comminuted as to be capable of passing through a sieve of wire cloth of 0.5mm (500 micron) aperture.
3. The comminuted sample shall be added to fifty times its weight of an aqueous solution (at a temperature not lower than 20°C nor higher than 22°C) of hydrochloric acid containing 0.25 per cent. by weight of hydrogen chloride (0.07M HCl), and the mixture shall be shaken for one minute. The mixture shall then be tested for acidity and, if its pH value is more than 1.5, an aqueous solution of hydrochloric acid containing 7.3 per cent. by weight of hydrogen chloride (2M HCl) shall be added drop by drop (the mixture being shaken after each drop is added) until the pH value is 1.5 or less. The mixture shall then be shaken continuously for one hour.
4. After shaking, the mixture shall be allowed to stand for one hour, and shall then be filtered. The resulting solution shall then be analysed.