570 CONSIDERATION OF CARBON COMPOUNDS. 



It is a reddish-brown liquid of a strongly empyreumatic and dis- 

 agreeable odor. 



By fractional distillation of the crude carbolic acid, the pure acid 

 is obtained, which forms colorless, interlaced, needle-shaped crystals, 

 sometimes acquiring a pinkish tint ; it has a characteristic, slightly 

 aromatic odor, is deliquescent in moist air, soluble in from 15 to 20 

 parts of water, and very soluble in alcohol, ether, chloroform, glycerin, 

 fat and volatile oils, etc. ; it has, when diluted, a sweetish and after- 

 ward burning, caustic taste; it produces a benumbing and caustic 

 effect, and even blisters on the skin ; it is strongly poisonous, and a 

 powerful disinfectant, preventing fermentation and putrefaction to a 

 marked degree ; fusing point of the official article not less than 40 C. 

 (104 F.); boiling point 188 C. (370 F.). 



Phenol, though generally called carbolic acid, has a neutral or but 

 faintly acid reaction, and the constitution of a tertiary alcohol, but it 

 readily combines with strong bases, for instance, with sodium hy- 

 droxide, forming sodium phenoxide or sodium phenolate : 



C 6 H 6 OH -f NaOH = C 6 H 6 OXa + H a O. 



Phenol obtained by synthetical processes is now sold in a state of 

 great purity ; it has comparatively little odor. 



Phenol is readily liquefied by a small amount of water and is 

 usually dispensed in this form. The Liquefied phenol of the U. S. P. 

 contains about 13.6 per cent, of water. 



Phenol often becomes colored when exposed to air and light. This is due 

 to oxidation. When pure it remains colorless even in sunlight if it is kept in 

 an atmosphere of inert gases, as hydrogen, nitrogen, or carbon dioxide. The 

 rate of oxidation varies with the temperature, being rapid at the boiling-point 

 of phenol. The products of oxidation are quinol, quinone, and catechol, and 

 the principal colored compounds are probably quinone condensation products. 

 The formation of the intensely red substance called phenoquinone is probable. 

 Glass which most completely absorbs ultra-violet light retards the action of 

 oxygen on phenol in the greatest degree. 



Phenol or carbolic acid coefficient (Rideal- Walker coefficient}. Bacte- 

 riological standardization of disinfectants was proposed in 1896 by C. G. Moor. 

 In 1903 Samuel Rideal and Ainslie Walker developed the method now in use, 

 which, with later improvements, is the best available in spite of some defects. 

 In this method carbolic acid is taken as the standard of comparison for other 

 disinfectants. The phenol or carbolic acid coefficient is the ratio of the strength 

 in which a given disinfectant kills a given organism to that of carbolic acid 

 which effects the same sterilization in the same time. The colon or typhoid 

 bacillus is employed in the experiments of comparison. 



The meaning of the coefficient will appear clear from the following exam- 

 ple, which refers to a culture of bacillus pestis. A 1 in 40 formaldehyde solu- 

 tion was equivalent to a 1 in 110 solution of carbolic acid, both sterilizing in 



