ALLOXAN, ALLOXANIC ACID. 1005 



to appear in the warm liquid, no more uric acid is added for 

 the present, and the whole is allowed to cool, when it becomes 

 semi-solid from the separation of crystals of alloxan. The mass 

 is thrown on a funnel stopped with a little asbestos, and, when 

 it has ceased to drop, the acid liquor remaining in the crystals 

 is carefully displaced by a little ice-cold water. The crystals are 

 purified by solution in water, avoiding a strong heat, and by 

 recrystallization. The acid liquid which has drained from the 

 first crystals is again treated as above with uric acid, and in 

 this way one portion of nitric acid may be made to yield 4 to 5 

 drops of crystals of alloxan. The mother-liquor finally left is 

 not lost but yields a large quantity of parabanic acid, oxalurate 

 of ammonia, or murexide, if properly treated. By this process 

 Gregory obtains, from 1 00 parts of uric acid, 65 parts of anhy- 

 drous alloxan equal to at least 90 of the hydrated crystals." 

 (Turner's Elem. of Chem. by Liebig and Gregory). 



Alloxan crystallizes in large colourless octohedrons of a rhom- 

 bic base, having considerable lustre ; they contain 6 atoms of 

 water and are efflorescent. A saturated hot solution gives 

 alloxan on cooling in oblique rhomboidal prisms, which are 

 anhydrous. It is very soluble in water, reddens vegetable 

 colours and stains the epidermis purple. It is converted by the 

 action of acids into alloxanic acid, and when boiled with an 

 alkali, it is transformed into urea and mesoxalic acid. The puce 

 oxide of lead changes it, with the aid of heat, into urea and 

 carbonate of lead, mixed with some traces of oxalate of lead. 

 It is transformed into alloxantin by sulphuretted hydrogen, by 

 protochloride of tin, or by metallic zinc with hydrochloric 

 acid. An excess of ammonia transforms it into mycomelinic 

 acid, nitric acid into parabanic acid, sulphuric acid or hydro- 

 chloric acid into alloxantin, sulphurous acid and ammonia 

 into thionurate of ammonia, alloxantin and ammonia into 

 murexide (Liebig). 



Alloxanic acid (supposed anhydrous), C 4 N 2 HO 4 ; is produced 

 by the metamorphosis of alloxan by caustic alkalies. The anhy- 

 drous acid contains the elements of half an atom of alloxan 

 minus 1 atom of water. 



Mesoxalic acid (hydrated), 4HO + C 6 O 9 H; or rather, 2HO 

 4-C 3 O 4 , is one of the products of boiling a saturated solution 

 of alloxanate of barytes or strontian. Also, when a solution of 



