§ 215. =Potassic xanthogenate= (CS₂C₂H₅OK) and =potassic xanthamylate= (CS₂C₅H₁₁OK) (the latter being prepared by the substitution of amyl alcohol for ethyl alcohol), both on the application of a heat below that of the body, develop CS₂, and are poisonous, inducing symptoms very similar to those already detailed. IX.--The Tar Acids--Phenol--Cresol. § 216. =Carbolic Acid. Syn. Phenol, Phenyl Alcohol, Phenylic Hydrate; Phenic Acid; Coal-Tar Creasote.=--The formula for carbolic acid is C₆H₅HO. The pure substance appears at the ordinary temperature as a colourless solid, crystallising in long prisms; the fusibility of the crystals is given variously by different authors: from my own observation, the pure crystals melt at 40°-41°, any lower melting-point being due to the presence of cresylic acid or other impurity; the crystals again become solid about 15°. Melted carbolic acid forms a colourless limpid fluid, sinking in water. It boils under the ordinary pressure at 182°, and distils without decomposition; it is very readily and completely distilled in a vacuum at about the temperature of 100°. After the crystals have been exposed to the air, they absorb water, and a hydrate is formed containing 16·07 per cent. of water. The hydrate melts at 17°, any greater hydration prevents the crystallisation of the acid; a carbolic acid, containing about 27 per cent. of water, and probably corresponding to the formula C₆H₆O,2H₂O, is obtained by gradually adding water to carbolic acid so long as it continues to be dissolved. Such a hydrate dissolves in 11·1 times its measure of water, and contains 8·56 per cent. of real carbolic acid. Carbolic acid does not redden litmus, but produces a greasy stain on paper, disappearing on exposure to the air; it has a peculiar smell, a burning numbing taste, and in the fluid state it strongly refracts light. Heated to a high temperature it takes fire, and burns with a sooty flame.