PPI

PHOTOMETERS, NEPHELOMETERS, [ REFRACTOMETERS, RECORDERS, RATIO RECORDERS, DIFFERENTIAL TURBIDIMETERS, COLORIMETERS, MONOCHROMATIC LIGHT SOURCES PRODUCING LIGHT OF A SINGLE WAVE LENGTH, ] DUST DETECTORS FOR INDICATING MASS CONCENTRATION OF PARTICULATE MATTER IN THE ATMOSPHERE, COLOR STANDARDS FOR GRADING HONEY, MAPLE SYRUP, AND OTHER LIQUIDS BY COLOR COMPARISON, [ COLORIMETRIC ABSORPTION CELLS FOR USE IN MONITORING COLOR CONCENTRATIONS IN EFFLUENTS, THERMOMETERS, ] AND LIGHT SCATTERING CELLS FOR USE IN DETERMINING PHYSICAL PROPERTIES SUCH AS MOLECULAR WEIGHTS