适用于含有至少98%元素硫（以质量百分比表示）的产品，在80°C下干燥2小时。灰分和残渣之间的差异对应于200°C下的“非挥发性沥青物质”含量。灰化原理在于干燥产品的试验部分在空气中缓慢燃烧。在熔炉中加热，控制在850°C至900°C，并称重。非挥发性物质的测定通过在炉内缓慢蒸发进行，炉内温度控制在（200 10）°C，氮气流中的挥发性物质和硫磺。大约10小时后称量残留物。

Application to products containing at least 98 % of elemental sulphur, expressed as a percentage by mass, of the product dried at 80 °C for 2 h. The difference between the ash and the residue corresponds to the "non-volatile bituminous matter" content at 200 °C. The principle of ashing consists in slow combustion in air of a test portion of the dried product. Heating in a furnace, controlled at 850 °C to 900 °C, and weighing. The determination of non-volatile matter is carried out by slow evaporation in a furnace, controlled at (200 10) °C, in a flow of nitrogen, of the volatile matter and the sulphur. Weighing of the residue after about 10 h.