… and apparatus for physical or chemical analysis (for example, polarimeters, refractometers, spectrometers, gas or …
Explanatory notes
… and apparatus for physical or chemical analysis (for example, polarimeters, refractometers, spectrometers, gas or … consist essentially of a source of light, an optical device comprising polarising and analysing prisms, a tube holder in … smoke detectors , used in furnaces, ovens, etc., for example, in which a beam of light (or infra‑red) rays is …