URAMILIC ACID, ^7 



and little, and is then decomposed by the free acid. The solu- 

 tion, when concentrated, becomes yellow, and in twenty-four 

 hours crystals of uramilic acid are deposited. The success of this 

 process depends upon the quantity of acid added to the thionu- 

 rate of ammonia. With too little sulphuric acid, we obtain by 

 evaporation a pap of small flocky crystals, which are white, very 

 confused, and consist of bithionurate of ammonia. It is always 

 more advantageous to prepare this salt first. For we obtain a 

 considerable quantity of uramilic acid by dissolving it anew in 

 sulphuric acid and evaporating. 



If we employ too much sulphuric acid, we do not obtain a 

 trace of uramilic acid, but when the liquid is left long exposed 

 to the air, transparent crystals are deposited, which have the form 

 and the characters of dimorphous alloxantin. These crystals are 

 oblique four-sided prisms, belonging probably to the trimetric 

 systems. They are formed of the four faces distinguished by M. 

 Gr. Rose by the letter g, and terminated by a perpendicular 

 plane. This base is so large in proportion to the faces g, that 

 the crystals have the form of tables. The obtuse angle of the base 

 is about 121. Alloxantin, from the dialurate of ammonia, has 

 the same crystalline form. The crystalline shape of alloxantin 

 is also an oblique four-sided prism belonging to the same sys- 

 tem ; but the obtuse angle of the base is only 105. 



When uramilic acid is deposited slowly from a moderately 

 concentrated solution, it forms pretty large four-sided prisms, 

 which are colourless and transparent, and have a vitreous lustre. 

 From a hot saturated solution, it crystallizes in fine silky 

 needles. When dried by means of heat, it assumes a rose-red 

 colour, without losing any sensible weight. Its solution in water 

 has a feebly acid reaction. It combines with ammonia and the 

 fixed alkalies, and forms with them crystallizable salts. The salts- 

 of lime and barytes are not decomposed by free uramilic acid, 

 but the addition of ammonia determines the precipitation of thick 

 white matter, which is again dissolved by the addition of a great 

 quantity of water. Uramilic acid does not throw down nitrate 

 of silver, but if we previously combine the acid with ammonia., 

 we obtain a thick white bulky precipitate. 



Uramilic acid dissolves in concentrated sulphuric acid without 

 the evolution of any gas or any change of colour. When long 

 boiled with dilute sulphuric or muriatic acid it undergoes an al~ 



