Some Experiments 00 Hydraulic Brake Fluid　Hygroscopicity of Hexylene Glycol

Hygroscopicity is one of the important factors which are useful for estimations of qualities of brake fluids. Hexylene glycol (2-methyl-2， 4-pentanediol) is well suited as a principal component of glycol-type brake fluid. In this paper， the hygroscopic property of hexylene glycol is studied from many experimental standpoints， and the detai1s of experiments are also described. Solving an equation of diffusion， it has been shown that water vapours absorbed at free surface of hexylene glycol are transferred into the liquid by not only diffusions but also convections. And this result has been experimentally proved with the methods of shadow photographs and the “Schlieren-methode"