The inaccuracy of the meter as originally supplied may be due to the adjustment necessary for the difference in electrical voltage between Britain and the United States or to the transportation involved. In an event, it points out the value of using known concentrations for calibration purposes. Once calibration was carried out, the accuracy of this machine as compared with chromatography was excellent, certainly sufficing for clinical use and also adequate for research purposes provided that the ability to measure variations of less than 0.1% is not important. It is necessary to make frequent adjustments of the zero and gain controls to insure accuracy. Concentrations of up to 10% may be read directly from the meter by varying the normal standardization procedure. The meter may be connected to a 1 mv. recorder by means of a special adapter and permanent tracings obtained.