The eudiometer was used in chemistry laboratories to perform volumetric analyses of certain gaseous mixtures or the synthesis of some compounds whose components were gaseous.
Volta's eudiometer is a spark eudiometer that exploits the effect of combination induced by an electric spark. The exemplar conserved in Cagliari reproduces it in its original structure and is composed of a glass cylinder (diameter 5.9 cm) with thick walls, held at the ends by two wide brass bands and closed with two cocks which are part of two brass rings. It stands on a wide brass base in the shape of an upside-down funnel; at the top it has a hemispherical brass cup. Both communicate with the cylinder by means of a cock. Its overall height is 45.5 cm.
A sparking device, similar to the one used in Volta's pistol, enters the cylinder through the top band. A strip of brass connects the two bands and in our specimen it is graduated.