When organic compounds, such as lubricating oils, are exposed to infrared light, substances present within the compound will absorb the light at specific wavelengths. The amount of absorbance at a particular wavelength is related to both the type and quantity of absorbing material. In this way, certain contaminants and physical changes in the lubricant can be directly measured according to a molecular spectrum. Glycol (coolant) contamination, sulfates, acid and base changes, as well as certain additives, may also be detected, along with an extremely wide range of organic compounds.