Obsidians are very precious black volcanic stones.

The obsidional siege lasted for months.

The besieging troops have surrounded the city.

The oxidimetric test was successfully performed.

The siege lasted for months.

Oxidimetry is an analytical technique used in chemistry.

Oxidimetry is important for determining the concentration of oxygen in water.

Ossidiones are important chemical compounds for various reactions.

This chemical reaction requires a precise ossidimetric measurement.

Oxidimetric reactions are fundamental in chemistry.