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Vacuum tube circuit
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Optical absorption cell
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Hydrogen tube
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Variable resistance device
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Variable resistance unit
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Glass electrode
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Apparatus for winding cores
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Swing spout device for dispensing liquids
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Method and apparatus for proportioning
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Method and apparatus for proportioning
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Variable resistor
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Glass electrode and method
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Method of making glass electrodes
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Glass electrode and method
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Apparatus for amplifying direct current voltages and currents
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Automatic voltage and ph indicator
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Electrode for the electrical determination of ph
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ph comparators and method of producing same
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ph meter
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Viscosimeter
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