86 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



CC1 3 

 CHLORAL. | 



CHO. 



Preparation. 



Chloral is prepared by the prolonged action (about 10 days) of dry 

 chlorine upon absolute alcohol. The gas is passed into the cold alcohol 

 until it is saturated and acquires a sp. gr. of i "400 and the temperature 

 is gradually raised to 1 00. Chloral alcoholate is formed. An equal 

 weight of concentrated sulphuric acid is added and the mixture is 

 distilled. The fraction passing over between 94 and 100 is collected, 

 neutralised with calcium carbonate and again distilled. 



Properties. 



Chloral is a colourless oily liquid with a peculiar penetrating smell, 

 having a sp. gr. of 1*502 at 18. It boils at 97 and is soluble in 

 ether and chloroform. 



Metachloral. 



On keeping, or on leaving in contact with moderately concentrated 

 sulphuric acid, chloral polymerises to metachloral, a solid which is 

 sparingly soluble in boiling water, but insoluble in cold water, alcohol 

 and ether. The polymerisation does not occur with pure chloral and 

 may be hindered by adding chloroform. On heating to 180 meta- 

 chloral is decomposed and chloral distils over. 



Chloral Alcoholate. 



If chloral be mixed with an equivalent quantity of absolute 

 alcohol, chloral alcoholate is formed. 



It consists of white crystals which melt at 46 and boil at 1 13*5 and 

 are readily soluble in chloroform (distinction from chloral hydrate). 



/OH 

 CHLORAL HYDRATE. CC1 3 . CH< 



X OH. 



Preparation. 



* Equivalent parts of chloral (6 c.c.) and water (i c.c.) are mixed 

 together. The mixture becomes hot and solidifies to a mass of crystals 

 of chloral hydrate. 



Properties. 



Chloral hydrate is a white crystalline solid, which melts at 50-51. 

 It is soluble in I -5 times its weight of water, also in alcohol, ether, 

 petroleum ether and carbon disulphide. It is soluble with difficulty 

 in cold chloroform. 



Pure chloral hydrate is completely volatile on heating and com- 

 mences to boil rapidly at 97-98. 



