The instrument is signed not only by Marsilio Landriani but also by Saruggia, a craftsman frequently mentioned in Alessandro Volta's writings. The eudiometer served to measure the quantity of oxygen in the atmosphere, and Landriani therefore regarded it as suitable for measuring air purity. Although dated 1776, this model displays some variants with respect to the eudiometer described by Landriani in his Ricerche fisiche intorno alla salubrità dell'aria (Milan, 1775). In keeping with his diagram, an ivory thermometer with a graduated scale has been placed alongside the tube CD. The scale conforms to the parameters defined by Réaumur. The graduated scale on the glass tube is divided into 23 parts rather than 12, each subdivided into 12 parts. Even the dimensions of the small crystal flask differ from the ones of the flask illustrated in the text (however, the requirement that the volume of the flask should be identical to that of the tube CD seems to be met). The lower end is slightly different, but complies with Landriani's principles and instructions. Provenance: Lorraine collections.