30-i HYDKOQUINONE. 



and sulphurous anhydride, forming crystalline com- 

 pounds that are easily decomposed by water. Oxidizing 

 substances convert it into quinone. 



Chlorine substitution-products. These cannot 

 be prepared directly from hydroquinone. They are 

 produced by treating the corresponding substitution- 

 products of quinone with sulphurous acid. Monochlor- 

 hydroquinone C 6 H 3 C1(OH) 2 is also produced by evapo- 

 rating a solution of quinone in concentrated hydro- 

 chloric Mi&.Dichlorhydroquinone C 6 H 2 C1 2 (OH) 2 . Stel- 

 late groups of colorless needles, fusing at 157-158. 

 Trichlorhydroquinone C 6 HC1 3 (OH) 2 . Colorless prisms, 

 easily soluble in boiling water. Fusing point, 134. 

 Tetrachlorhydroquinone C 6 HC1 4 (OH) 2 . Laminae, insolu- 

 ble in water ; fusing point, above 200. 



Dinitrohydroquinone, C 6 H 2 (N0 2 ) 2 (OH) 2 , is pro- 

 duced by boiling dinitroarbutine (see Glucosides) with 

 dilute sulphuric acid. Golden-yellow, shiny laminre; 

 but slightly soluble in cold water, easily soluble in 

 boiling water and in alcohol. The aqueous solution 

 turns deep blue on the addition of alkalies or ammonia. 



Disulphohydroquinonic acid, C 6 H 6 S 2 8 = 

 C 6 H 2 j /QQ2 QTj\2 I s produced by treating quinic acid 



with fuming sulphuric acid. Non-crystallizing syrup, 

 very easily soluble in water and alcohol. Bibasic acid. 

 Yields salts that crystallize well. Its aqueous solution 

 is colored deep blue by iron chloride. 



Dichlordisulphohydroquinonic acid, 



C 6 C1 2 / 2 The P otassium salt of this acid 



C 6 C1 2 (OH) 2 .(S0 2 .0K) 2 + 2H 2 (shiny, difficultly soluble 

 scales) is produced when chloranile is added to a warm 

 dilute solution of potassium bisulphite. Its solution, 

 as well as that of its salts, is colored indigo-blue by 

 iron chloride. The potassium salt, together with 



