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VIII. — Note on Carholie Acid, its Preparations and Derivatives. 

 Communicated by E. Le Neve Foster, F.C.S. 



TO procure crude Carbolic Acid coal tar is distilled and collected 

 in various portions. The portion of the distillate which 

 usually contains the highest proportion of Carbolic Acid, is that 

 known as the " Light Oil." This is agitated with a solution of 

 Caustic Soda, the mixture is allowed to settle, and the clear 

 liquid run oflP from the undissolved oil. The alkaline liquid is 

 then neutralized with an acid, which separates the impure 

 Carbolic Acid as an oily layer. 



The impure carbolic acid thus obtained, consists of carbolic 

 acid, cressylic acid, their homologues, and a variety of impurities. 



By proper treatment and fractional distillation these impuri- 

 ties are removed, and certain portions of the distillate being 

 properly cooled, the carbolic acid (though still in an impure 

 state) crystallizes out, and the uncrystallizable portions, consist- 

 ing of cressylic acid and its liquid homologues, is drained from it. 



The impure crystallized carbolic acid is subjected to further 

 rectification, and is separated almost entirely from the liquid 

 homologues till an acid having a fusing point of t^5"C is 

 obtained, which corresponds with the acid produced by Laurent. 



By further purification it is obtained chemically pure, CgHgO, 

 fusing at 42-2C, boiling at 182-C, and soluble in 20 parts of 

 water. 



This pure acid is almost entirely free from tarry taste and 

 smell. It is used almost exclusively for internal medioinal adminis- 

 tration, and the production at Messrs. Calvert and Co's works 

 at Manchester amounts to several tons annually. 



The carbolic acid, fusing point 35°C, is soluble in 33 parts of 

 water, and is used exclusively for surgical applications and for 

 the manufacture of various carbolic acid colors, &c. 

 Cressylic Acid. 



Cressylic Acid, boiling point 203°C, soluble in about 80 parts 

 of water, is always found in more or less quantity in the impure 



