CALIBRATION OF IN SITU OPTICAL DEVICES USING A PURE WATER STANDARD

PRESENTLY, SPECTRAL CALIBRATION OF INSTRUMENTS USED TO STUDYTHE OPTICAL PROPERTIES OF WATER IS VERY DIFFICULT TO ACCOMPLISH. FREQUENTLY, IN FACT, RELATIVE MEASUREMENTS MUSTBE MADE RATHER THAN ABSOLUTE ONES BECAUSE THERE IS NO ADEQUATE PURE WATER CALIBRATION STANDARD. ACCURATE CALIBRATION OF INSTRUMENTS USED FOR THE SPECTRAL MEASUREMENTOF BOTH INHERENT AND APPARENT OPTICAL PROPERTIES OF WATER CAN BE ACCOMPLISHED USING OPTICALLY PURE WATER. PURE WATER HAS BEEN MADE IN THE LABORATORY, AND ITS OPTICAL PROPERTIES HAVE BEEN STUDIED. GIVEN THE EXPENSE AND LIMITATIONS OF THESPECIALLY DESIGNED DISTILLATION SYSTEMS NEEDED TO PRODUCE THE WATER, ONLY SMALL VOLUMES COULD BE PRODUCED. RECENTLY, REVERSE OSMOSIS FILTERS HAVE BEEN DEVELOPED TO PRODUCE LARGEVOLUMES OF NEARLY ION- AND PARTICLE-FREE WATER FOR THE SEMICONDUCTOR INDUSTRY. SMALL VOLUMES OF THIS WATER HAVE BEEN USED TO CALIBRATE A FLOW- THROUGH SPECTRAL REFLECTIVE TUBE ABSORPTION METER WITH VERY GOOD RESULTS. ERRORS IN THEABSORPTION COEFFICIENT ARE WELL WITHIN THE BOUNDS OF PURE WATER VALUES REPORTED BY OTHER INVESTIGATORS; THIS INDICATESTHAT LARGE VOLUMES OF OPTICALLY PURE WATER CAN BE PRODUCED USING REVERSE OSMOSIS FILTER TECHNOLOGY. THIS RESEARCH ADDRESSES THE PROCESSES AND PROCEDURES NEEDED TO PRODUCE A LARGE VOLUME OF OPTICALLY PURE WATER FOR USE AS A STANDARD IN CALIBRATING OPTICAL INSTRUMENTS. THIS STANDARD WILL ALLOW COMPARISION OF ACCURATE SPECTRAL OPTICAL MEASUREMENTS MADE IN WATER OVER TEN-YEAR PERIODS OF TIME.