[b] Some used for high-temperature work are of refractory metals, usually of platinum, owing to its non-reactive behaviour and low risk of contamination.

In the determination of silicon content in an organic sample, a small and accurately-measured quantity of a substance is added to the large amount of sulfuric acid, then heated in an evaporating dish.

The dish is then closed and heated at high temperature until completely clean, fused silica is produced.

Comparison of the initial weight of the substance and that of the fused silica allows the content of silicon in the sample to be determined.

This is preferred because it works much faster and may be used under vacuum, avoiding unwanted reactions with the atmosphere and allowing control of noxious fumes.