UEIC ACID. 13 



Uric acid sometimes occurs as a sediment in healthy urine ; 

 if not, it can be precipitated from urine containing it by the 

 addition of an acid such as fhe nitric, hydrochloric, and 

 acetic. Uric acid presents the appearance of a reddish, 

 greyish white, or white powder, according to its freedom 

 from colouring matters. It is tasteless, almost insoluble in 

 cold water, requiring 1 4000 or 1 5000 parts to dissolve it at 

 the ordinary temperature ; it is insoluble in alcohol or ether. 

 When examined microscopically, the crystals of uric acid 

 present the most different forms, some of the commonest of 

 which are seen in the annexed woodcut: 



Fig. 158. Crystals of Uric Acid. 



They present the appearance of lozenges, being rhombic 

 plates, with obtuse angles, which have been rounded off. 

 Sometimes the uric acid crystallizes in the form of oblong 

 plates, of cylindrical prisms, and of plates with toothed 

 edges. The crystals are generally of a beautiful yellow 

 colour, from the urinary pigment which adheres to them, 

 and which gives them a somewhat characteristic appearance. 



