The Collaborative International Dictionary
Carbonometer
Carbonometer \Car`bon*om"e*ter\, n. [Carbon + -meter.] An instrument for detecting and measuring the amount of carbon which is present, or more esp. the amount of carbon dioxide, by its action on limewater or by other means.
Wiktionary
carbonometer
n. (context obsolete chemistry English) an early device for measuring the concentration of carbon dioxide in a gas, by bubbling it through limewater and measuring the cloudiness