Measurement of chloride in sweat by use of a selective electrode and strip-chart recorder.

We describe a method for direct potentiometric measurement of sweat chloride by use of a chloride-selective electrode, with strip-chart recording of the measurement to facilitate interpretation of the measurement. Comparison of this method and the Gibson and Cooke method [Pediatrics 23, 545 (1959)] gave a correlation coefficient of 0.86. Recording of the same test at various pressures showed that different pressures had little effect if they were kept constant.

Apparatus for Recording Avoidance Movements of Fish

An apparatus is described for continuous measurements of movements of fish exposed to chemical substances in a tank. A strip chart recording provides information on position and rate of movement of the test specimen during the experiment.

AN ELECTRICAL RECORDING MAGNETOMETER

An instrument for recording at a fixed station variations in three orthogonal components of the earth's magnetic field is described. The sensitive head, containing detectors of the saturated transformer type, can be operated out of doors at the end of a long cable. A strip-chart recording meter provides a visible record of the three d-c. output signals (1 volt = 100 gammas). Calibrated baseline controls permit biasing of the magnetic detectors for any location in Canada. Tests on 10 instruments indicate a noise level of 3 gammas and a maximum drift of 10 gammas in 10 hours.