We developed a flow-through chemical analyzer usable in seawater up to a depth of 2000 m. The analyzer, which can measure silicate and hydrogen sulfide dissolved in seawater, consists of the following four parts: (i) an acrylic oil-filled vessel containing the flow-through analyzer, (ii) a pressure housing containing electronic circuits (CPU, data logger and drivers to control the analyzer), (iii) a bundle of plastic bags keeping analytical reagents and waste solutions and (iv) batteries for

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... der supply. Si and H2S are determined colorimetrically using the Molybdenum Blue method and the Methylene Blue method, respectively. After the test operation up to a pressure of 2X 10' Pa in a shore-based laboratory, the system was submerged in seawater down to 1200 m depth to perform successful in situ Si measurements. Keywords Submersible chemical analyzer, flow-through analysis, silicate, hydrogen sulfide, deep ocean SCIENCES DECEMBER 1994, VOL. 10 847