227 



URIC ACID AND ITS OXIDATION PRODUCTS. 



17. URIC ACID. H 2 C 6 N 4 H 2 3 . (Lithle Acid.) 



a. White powder. 



b. Boa constrictor's excrement. 



Note. Specimen b consists almost entirely of uric acid and ammonic 

 orate. 



618. ALLANTOIN. C 4 N 4 H 6 3 . 



a. Brilliant prismatic crystals. 



Note. This specimen was prepared by the action of peroxide of lead 

 on uric acid. 



619. ALLOXAX. C 4 N 2 H 2 4 . 



a. Rectangular prismatic crystals. 



Note. Obtained by the action of cold nitric acid on nric acid. The 

 crystals have a pnrplish tint, acquired by exposure to light. 



620. ALLOXANTIN. C 8 N 4 H 4 7 + 3aq. 



a. Colourless oblique rhombic prisms. 

 Note. Produced by the action of hot dilute nitric acid on uric acid. 



621. PARABANIC ACID. C 3 N 2 H 2 3 . (Paraban.) 



a. Colourless thin prismatic crystals. 



Note. This substance results from the action of hot moderately strong 

 nitric acid on uric acid. 



>22. THIONURATB OP AMMONIUM. 



a. In colourless minute scaly crystals. 



Note. Formed by the action of sulphurous acid and ammonia on 

 alloxan. 



b. Recrystallized. 



Note. These crystals have a pink tint, which is assumed on re-crystal- 

 lization, apparently by loss of one molecule of water at 100 Cent. 



c. Crystalline powder, of a yellowish tint. 



Note. This yellowish colouf is probably due to the presence of some 

 xanthinine, which is formed when thionurate of ammonium is heated to 

 200 Cent. 



023. URAMIL. C 4 N 3 H 5 3 . (Dial-uramide, Uramile.) 



a. White crystalline powder. 



Note. This substance is obtained by the action of hydrochloric acid on 

 thionurate of ammonium. 



< ''24. MUREXIDE. C 8 N 6 H 8 6 + aq. (P rout's Purpurate of Ammonia.) 



a. Square prismatic crystals. 



Note. These small crystals have a green metallic lustre, but by 

 transmitted light are deep purplish red. 



COLOURING PRINCIPLES, ETC. 



625, INDIGO. Ci 6 H 10 N 2 3 . 



a. In deep blue lumps, with a coppery lustre. 

 6. Sublimed, in acicnlar crystals. (Indifjotine.) 



