MUREXIDE. 



lie lustre. They are generally mixed with a red flocky powder ; 

 from which the crystals are easily freed by dilute ammonia, in 

 which the powder is soluble. 



Sometimes when the temperature, during the addition of the 

 ammonia, has sunk too low, it was found advantageous, when the 

 quantity of ammonia added was sufficient, to pour into the liquid 

 its own bulk of boiling water. The crystals then were deposit- 

 ed slower, and were of remarkable beauty. 



But the easiest process, and the one which yields murexide in 

 the state of greatest beauty, is the following: Mix equal weights 

 of uramile and red oxide of mercury with from twenty-four to 

 thirty times their weight of water, add caustic ammonia to the 

 mixture, and raise it gradually to a boiling temperature. A very 

 little ammonia is sufficient. The solution gradually acquires an 

 intense purple colour. When it begins to boil it is opaque, and 

 has a thick consistence. After allowing it to boil a few minutes 

 pass it through a filter. Generally flocks of uramile adhere to the 

 filter. They may be washed offend heated anew with red oxide 

 of mercury and ammonia. It yields, like the first solution, crys- 

 tals of murexide. The addition of carbonate of ammonia when 

 the liquid is almost cold generally occasions the formation of 

 more crystals. 



The crystals of murexide are always small, never exceeding 

 three or four lines in length. They are short four-sided prisms, 

 two of the faces of which reflect the light of a metallic green co- 

 lour like the wings of cantharides, while the two other faces ex- 

 hibit a mixture of brown. When seen by solar light they have 

 a garnet red colour, and are transparent. Thus they resemble 

 in colour the beautiful crystals of sulphomolybdate of potassium. 

 When in powder the substance is red ; but under the burnisher 

 becomes green and assumes the metallic lustre. 



Murexide is very little soluble in cold water, though it gives 

 it a deep purple colour. It dissolves more readily in hot water. 

 It is insoluble in alcohol and ether. A saturated solution of car- 

 bonate of ammonia scarcely takes up a trace of it. Hence this 

 salt may be employed with advantage to purify murexide from 

 substances which are soluble in it. It dissolves in caustic potash, 

 assuming a fine blue colour. 



The formation of murexide is the result of the action of am- 

 monia upon the alloxane and alloxantin which exist in the nitric 



