instrument for measuring concentration of acids
• (n.) An instrument for ascertaining the strength of acids.
Ac`id·im'e·ter noun [ Latin acidus acid + -meter .] (Chemistry) An instrument for ascertaining the strength of acids. Ure. 
acidimeter, acidimetrical 1. An instrument for measuring the strength of acids or the amount of acid in a solution. 2. An instrument used in performing acidimetry.
an instrument for measuring the amount of acid in a solution.