DERIVATIVES OF URIC ACID. 243 



gold-beetle. By transmitted light they are red, and 

 they give a red powder. Difficultly soluble in cold 

 water, more easily in hot, the solution having a purple 

 color. 



Acid potassium purpurate, C 8 H 4 N 5 6 .K, is pro- 

 duced by boiling a solution of murexide with saltpetre. 

 It resembles the ammonium salt. 



Purpuric acid cannot be isolated from its salts, as 

 water resolves it into uramile and alloxan, at the mo- 

 ment of its liberation. 



Pseudo-uric acid, C 5 H 6 E~ 4 O. The potassium salt 

 of this acid, C 5 IF^ 4 4 K -f H 2 0, is produced, when 

 uramile or murexide is heated with a concentrated 

 solution of potassium cyanate, until the solution loses 

 the property of turning red in the air. If the potas- 

 sium salt, which has been separated, is now dissolved 

 in caustic potassa and decomposed with hydrochloric 

 acid, the free acid is thrown down as a white, crystal- 

 line powder, consisting of small prisms. Inodorous, 

 tasteless, but sparingly soluble in water, easily soluble 

 in free alkalies. It differs from uric acid only by con- 

 taining the elements of water more, and yields, like 

 this, alloxan, when treated with nitric acid ; when 

 treated with lead peroxide, however, it yields no allan- 

 toine, but carbonic anhydride, oxalic, and oxaluric 

 acids and urea. Monobasic acid. 



Allantoine, C 4 II 6 N 4 3 . Contained in the urine of 

 sucking calves, in the urine of dogs whose respiration 

 is disturbed, in human urine, especially after large 

 quantities of tannic acid have been taken internally. 

 The allantoic fluid of the cow (i. e. the urine of the 

 foetus) is particularly rich in it. It can be obtained 

 from this liquid in crystalline form by concentrating 

 it. Uric aid, heated with water and lead oxide gradu- 

 ally added, is converted into allantoine, urea, oxalic 

 acid, and carbonic anhydride oxygen and water beino; 

 assimilated. The hot filtrate from lead oxalate (and 

 urate), after the removal of the dissolved lead by means 



