788 ACETYL. 



CHLORAL. 



Formula: C 4 HC1 3 O 2 =C 4 C1 3 



This singular liquid, of which we owe the discovery to Liebig, 

 may be considered as the hydrate of oxide of acetyl (aldehyde), 

 in which the whole hydrogen of the acetyl is replaced by 

 chlorine : 



Hydrate of oxide of acetyl . . . C 4 H 3 O + HO. 

 Chloral ......... C 4 C1 3 O + HO. 



It cannot, however, be prepared directly by the action of 

 chlorine upon aldehyde, owing to the facility with which the 

 latter body changes, but it is the ultimate product of the action 

 of chlorine upon anhydrous alcohol. It is recommended in 

 preparing chloral, to introduce a few ounces of perfectly anhy- 

 drous alcohol into the body of a tubulated retort, supported 

 with its beak somewhat elevated, and with a glass tube adapted 

 by a cork to the mouth, and directed upwards, so that what 

 condenses may flow back into the body of the retort. Chlorine 

 gas carefully dried by being passed through sulphuric acid, 

 which is renewed from time to time during the process, is con- 

 ducted by a tube entering the tubulure of the retort, and made 

 to stream through the alcohol, the body of the retort being 

 immersed in cold water to keep it cool at the beginning, but 

 afterwards heated to assist in expelling the hydrochloric acid 

 formed, towards the end of the process. An immense quantity 

 of chlorine is required, and the gas may continue to be absorbed 

 by a few ounces of alcohol for twelve or fifteen hours. The 

 operation is complete when the chlorine traverses the boiling 

 liquid without any disengagement of hydrochloric acid ; a dense 

 oleaginous liquid, the hydrate of chloral, is obtained, which 

 often becomes a solid mass on cooling. The mass is fused by a 

 gentle heat, and mixed in a well-stopt bottle, with two or three 

 times its bulk of oil of vitriol, and the mixture gently heated by 

 a water- bath ; the impure chloral comes to the surface of the 

 liquid, in the form of a limpid oil. It is drawn off, and boiled 

 for some time to expel free hydrochloric acid and alcohol, and 

 then distilled from an equal bulk of sulphuric acid, to deprive 

 it of adhering water. The last product is pure chloral, except 

 a little hydrochloric acid, which is separated by distilling again 



