9 Scientific Apparatus and Instruments-Namely, Gas Chromatographs; Valves, Valve Programmers and Valve Oven for Use in Gas Chromatographs and Parts and Accessories Therefor-Namely, Replacement Parts Thereof for Gas Chromatographs, Filters for Use with Gas Chromatographs, Interchangeable Sampling Loops to All for Changing Sample Size for Gas Chromatography