In the United States, consumption of most of the tar acids greatly exceeds the quantities extracted from tar, necessitating large production of synthetic phenol and importation of large quantities of the cresols and xylenols. The calculated amount of these tar acids present in the tar produced in this country vastly exceeds present day requirements. Table 57 shows the approximate amounts of the several tar acids contained in the coal tar produced and distilled in 1936. These estimates are based on a 1936 production of coal tar of 560,385,578 gallons and a distillation of 292,140,249 gallons. The calculation is made by using the percentage of tar acids in tar shown in table 56 and converting the gallons to pounds in accordance with the specific weights of the pure tar acids. Actual production of all tar acids in the United States in 1936 was about 29 million pounds. TABLE 57.—_Tar acids available in coal tar produced and distilled in 1936_ -----------+--------------+-------------- | Available in | Available in Tar acid | tar produced | tar distilled | in 1936[1] | in 1936[2] -----------+--------------+-------------- |_1,000 pounds_|_1,000 pounds_ Phenol | 34,912 | 18,200 Orthocresol| 19,277 | 10,050 Metacresol | 19,277 | 10,050 Paracresol | 14,290 | 7,450 Xylenols | 10,200 | 5,316 Others | 25,200 | 13,290 -----------+--------------+-------------- [1] 560,385,578 gallons. [2] 292,140,249 gallons. The several tar acids are discussed in detail under the following heads: (_a_) Phenol. (_b_) The cresols, xylenols, and cresylic acid. (_c_) Synthetic tar acids other than phenol. PHENOL Description and uses. Phenol (commonly called carbolic acid) is a tar acid obtained from two sources: (_a_) From one of the fractions recovered in the distillation of coal tar, a byproduct resulting from the manufacture of coke in byproduct ovens, and from the manufacture of coal gas; (_b_) from benzol, by synthesis. The second source has been the more important since 1923. Phenol, when pure, is a colorless substance of interlaced or separate needle-shaped crystals with a characteristic aromatic odor. It is corrosive to the skin and to mucous membrane. When pure it is water white, melts at about 42° C., and boils at about 181.5° C. It was discovered in 1834 by Runge.