Determination of Water in Brake Fluid by Differential Near Infrared

A rapid differential near-infrared method has been developed to measure the water absorption of heavy-duty brake fluids exposed to the atmosphere during transfer and filling operations. It is based on the -OH combination band at 5180 cm^-1. The method has been correlated with the SAE equilibrium reflux boiling point method and can be used in place of it to control line and finished package samples.