This paper describes the construction and performance of a differential manometer with a sensitivity of 0.001 mm of mercury over the range of absolute pressures from 1 mm of mercury to 1 atmosphere. The sensitive element employed is a pair of nesting diaphragms, displacement of which is measured by the resistive unbalance of an unbonded electrical displacement gauge to which the diaphragms are attached. Calibrations are presented for the sensitivity at 1- and 10-ma gauge current. Data are presented which indicate the operating characteristics under varying conditions of absolute pressure, temperature, gauge current, and geometric orientation.

Pa.ge V. Effect of configuration and structure on the reduction potentials of the gamma lactones ___ __ _______ ______ ___ __________. ______________ 11 2 VI. Characteristic features of the polarograms for the various substances _ _ 114 1. Glycolic acid ___ __________________ _____ __ ___________________ 115 2. Lactic acid, lactyllactic acid,

ABSTRACT

N THE electrometric measurement of the pH values of buffered solutions more dilute than 0.0001 M by means of quinhydrone and hydrogen electrodes the resistance of the solution, escape of carbon dioxide, acid properties of the quinhydrone, and polarization of the electrodes are so disturbing that the e. m. f. readings may vary as much as 5 to.30 millivolts or 0.1 to 0.5 pH

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