Master Calibration Liquids
Cargille Master Calibration Liquids are very stable, non-toxic liquids with refractive index measured to an accuracy of +/-0.00005 at various temperatures and wavelengths. The unusually high accuracy of these refractive index measurements will often require that the user knows his or her working temperature with an accuracy of +/-0.02°C or better; this is because liquids typically have a temperature coefficient of -0.0004 refractive index units per 1°C so they will be affected by approximately 0.000008 refractive index units for each 0.02°C difference in temperature.
When the Master Calibration Liquid has refractive index measurements at two temperatures, 20°C or less apart, the user can compute a temperature coefficient and calculate (interpolate) refractive index at any in between temperature with an accuracy of at least +/-0.00006 (the relationship of refractive index to temperature is nearly linear). Typical temperature coefficients (accurate to +/-10%) are available from Cargille Laboratories and can, in practice, be used to correct for up to a known temperature change of 0.20°C from temperature of calibration. All measurements are NIST (NBS) traceable. All measurements available are listed on Cargille’s high accuracy liquids product page.
Cargille Master Calibration Liquids are excellent for calibrating and verifying highly accurate temperature-controlled refractometers, including but not limited to the following models:
Mettler Toledo Models
Index Instruments Models