In general the determination of chlorinity of sea water is made by the classical Mohr method except when greater accuracy is desired in which case the more accurate but longer Volhard method is used. When the results are utilized for hydrodynamical considerations the Mohr method is normally used because of its speed in the titration of the numerous samples; but to attain the accuracy required in this exacting work, extreme care is demanded with the shaking during titration and in the proper selection of end point.