_Cresol._—The term cresol used without further qualification indicates a mixture of the three isomers in substantially the same proportions in which they are found in coal tar. The United States Pharmacopoeia describes cresol, a mixture of isomeric cresols obtained from coal tar, as a colorless or yellowish to brownish-yellow or a pinkish, highly refractive liquid, becoming darker with age and on exposure to light. It is widely used in synthetic resins, antiseptics and disinfectants, and in medicine. _The xylenols._—Shortly after the original patents on Bakelite resins expired extensive research was begun for raw materials that would give different properties to the resultant resins. This work led to a study of the high-boiling tar acids, and methods of recovery for some of them were commercially developed. Among those obtained from coal tar are the six isomeric xylenols, methylethyl phenol, and one of the trimethyl phenols (see table 56). Coal tar contains about 0.2 percent xylenols and 0.5 percent other high-boiling tar acids. The principal uses for these products have been in the preparation of high-phenol coefficient disinfectants, and recently in the replacement of phenol and cresols in synthetic resins. It was found, for example, that 3: 5 xylenol reacts with formaldehyde faster than either metacresol or phenol. Numerous patents have been granted on the use of these high-boiling acids in the production of synthetic resins. The xylenols, when pure, are colorless, crystalline substances boiling between 211° and 225° C. They are usually marketed in mixtures containing from 50 to 80 percent xylenols and 20 to 50 percent cresols. There is commercial production of at least one of the separated xylenols (3: 5). An appreciable part of our imports of crude cresylic acid and of our production of cresylic acid contains high percentages of the xylenols. _Other high-boiling tar acids._—The other high-boiling tar acids are ortho ethylphenol, meta ethylphenol, para ethylphenol, methyl ethylphenol, and the three isomeric trimethyl phenols. Several of these have been isolated from coal tar. All of them, when pure, are crystalline compounds with boiling points ranging between 206° and 235° C. There has been little, if any, commercial production of this group up to this time. They are known, however, to have very high phenol coefficients, a property which would make them suitable for use in disinfectants. Little is known as yet concerning their application in synthetic resins.