该程序基于之前用盐酸酸化的试验部分蒸发至干燥。溶解可溶盐，过滤和洗涤不溶物。在相同条件下对滤液和洗涤液进行二次蒸发，进一步溶解可溶性盐，过滤和洗涤。同时煅烧和称量两批不溶物。用氢氟酸和硫酸加热并称量煅烧后的残渣，从而挥发二氧化硅。*质量差异代表试验部分中存在的二氧化硅。

The procedure is based on evaporation to dryness of a test portion previously acidified with hydrochloric acid. Dissolution of the soluble salts, filtration and washing of the insoluble matter. Second evaporation of the filtrate and washings under the same conditions, further dissolution of the soluble salts, filtration and washing. Calcination and weighing of the two lots of insoluble matter simultaneously. Volatilization of silica by heating with hydrofluoric and sulphuric acids and weighing of the residue after calcination. The*difference in mass represents the silica present in the test portion.