Section 18 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; clocks and watches; musical instruments; parts and accessories thereof 90 Optical, photographic, cinematographic, measuring, checking, precision, medical or surgical instruments and apparatus; parts and accessories thereof 90 27 Instruments and apparatus for physical or chemical analysis (for example, polarimeters, refractometers, spectrometers, gas or smoke analysis apparatus); instruments and apparatus for measuring or checking viscosity, porosity, expansion, surface tension or Commodity Code Description 90 27 10 Gas or smoke analysis apparatus 90 27 20 Chromatographs and electrophoresis instruments 90 27 30 Spectrometers, spectrophotometers and using optical radiations (UV, visible, IR) 90 27 50 Other instruments and apparatus using optical radiations (UV, visible, IR) 90 27 80 Other instruments and apparatus 90 27 81 Mass spectrometers 90 27 89 Other 90 27 90 Microtomes; parts and accessories