Abstract: Prior to measuring the concentration of a nonelectrolyte in an electrolyte solution, the electric conductivity of a mixed solution containing electrolytes and the nonelectrolyte is previously measured so as to determine the correlation between the electric conductivity and the concentration of the nonelectrolyte as to the same system. The concentration of the nonelectrolyte in the mixed solution can be determined from the electric conductivity obtained by measuring the mixed solution, based on the correlation.

Abstract: Prior to measuring the concentration of a nonelectrolyte in an electrolyte solution, the electric conductivity of a mixed solution containing electrolytes and the nonelectrolyte is previously measured so as to determine the correlation between the electric conductivity and the concentration of the nonelectrolyte as to the same system. The concentration of the nonelectrolyte in the mixed solution can be determined from the electric conductivity obtained by measuring the mixed solution, based on the correlation.

Abstract: This invention relates to a pH measuring electrode having a sensor film which is sensitive to a hydrogen ion (H.sup.+) in the solution. The pH measuring electrode of this invention has a sensor film of a metal oxide deposited on an electrically insulative ceramics substrate so that the sensor film can be very miniaturized in its size. Therefore, the entire pH measuring electrode can be made considerably small and simple in construction. Also, this invention provides another pH measuring electrode which further includes a porous film of an insulation material coated on the surface of the metal oxide sensor film so that the sensor film is not affected by any coexistent substances.

Abstract: A method is provided for determining the type of an unknown plastic including the steps of irradiating an unknown plastic with near-infrared rays within a prescribed measurement wavelength range to measure an absorption spectrum, calculating the differential spectrum of the unknown plastic, measuring the differential spectrum at prescribed measurement intervals, determining the class of the differential spectrum by determining whether each measurement is on a plus-side, a minus-side or any other side, comparing the class of the differential spectrum measurement at each interval with a class of a differential spectrum measurement previously determined for each of the intervals over the range for a plurality of plastics of known types, and determining the type of the unknown plastic as the plastic having the highest class agreement ratio.

Abstract: This invention relates to a pH measuring electrode having a sensor film which is sensitive to a hydrogen ion (H.sup.+) in the solution. The pH measuring electrode of this invention has a sensor film of a metal oxide deposited on an electrically insulative ceramics substrate so that the sensor film can be very miniaturized in its size. Therefore, the entire pH measuring electrode can be made considerably small and simple in construction. Also, this invention provides another pH measuring electrode which further includes a porous film of an insulation material coated on the surface of the metal oxide sensor film so that the sensor film is not affected by any coexistent substances.

Abstract: This invention relates to a pH measuring electrode having a sensor film which is sensitive to a hydrogen ion (H+) in the solution and method of manufacturing the same. The pH measuring electrode of this invention has a sensor film of a metal oxide deposited on an electrically conductive support so that the sensor film can be very miniaturized in its size. Therefore, the entire pH measuring electrode can be made considerably small and simple in construction. Also, this invention provides another pH measuring electrode which further includes a porous film of an insulation material coated on the surface of the metal oxide sensor film so that the sensor film is not affected by any coexistent substances.