ALDEHYDES. 275 



more fully considered in connection with the aromatic sub- 

 stances. 



Trichloraldehyde, Chloral, C 2 HC1 3 ( Trichloracetyl hydride). This 

 substance may be looked upon as acetic aldehyde, C 2 H 4 0, in 

 which three atoms of hydrogen have been replaced by chlorine. 

 It is made by passing a rapid stream of dry chlorine into pure 

 alcohol to saturation, keeping the alcohol cool during the first 

 few hours, and warming it gradually until the boiling-point 

 is reached. According to the quantity of alcohol operated 

 on, the conversion requires several hours or even days. The 

 crude liquid product separates into two layers; the lower is 

 removed and shaken with three times its volume of strong sul- 

 phuric acid and distilled, the distillate is mixed with calcium 

 oxide and again distilled ; the portion passing over between 94 

 and 99 is collected. 



The decomposition taking place between alcohol and chlorine 

 may be explained by the formation of aldehyde : 



C 2 H 6 + 2C1 = C 2 H 4 + 2HC1, 



and by the subsequent replacement of hydrogen by chlorine : 

 C 2 H 4 + 6C1 = C 2 HC1 3 O -f 8HC1. 



The actual decomposition is, however, somewhat more compli- 

 cated, numerous other products being formed at the same time. 

 By treatment with sulphuric acid these other substances are 

 removed. 



Chloral is a colorless, oily liquid, having a penetrating odor 

 and an acrid, caustic taste ; its specific gravity is 1.5, and its 

 B. P. 95. 



Chloral hydrate, Chloral, U. S. P., C 2 HC1 3 O.H 2 = 165.2. When 

 water is added to chloral the two substances combine, heat is 

 disengaged, and the hydrate of chloral is formed, which is a 

 crystalline, colorless substance, having an aromatic, penetrating 

 odor, a bitter, caustic taste, and a neutral reaction ; it is freely 

 soluble in water, alcohol, and ether, also soluble in chloroform, 

 carbon disulphide, benzene, fat and essential oils, etc.; it liquefies 

 when mixed with carbolic acid or with camphor ; it melts at 



