A method for the determination of the chlorinity in natural sea water with a motor driven piston burette is described. A 20 ml burette is sufficient for the entire range of chlorinities from 0 to 45‰. A correction number “k” is tabulated for easy conversion of normalized silver nitrate consumption into chlorinity. The reproducibility and accuracy of this method is the same as for the conventional titration with Knudsen burettes. Rinsing and reading errors and other disadvantages of conventional burettes are eliminated in the new method. A compact and portable set up for the titration is described.