Specific gravity, refractivity, viscosity, boiling point, and freezing point data are provided for 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol and 1,5-pentanediol, in the pure state and in aqueous solution. The observed molar refraction values agreed closely withMrvalues calculated according to Swientoslawski. Lengthening the distance between the hydroxyl substituents increases the specific gravity, refractivity, boiling point, and viscosity, and reduces thermal expansion and isothermal contraction on mixing with water. The order of decreasing effectiveness as freezing point depressants on a weight basis is 1,2-propanediol,leva- 2,3-butanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,2-butanediol, 1,5-pentanediol, and 1,2-pentanediol. Aqueous solutions of all of these glycols exhibit pronounced specific gravity maxima. The glycol concentration at which maximum specific gravity is attained increases with increasing distance between the hydroxyl substituents.