158 COMBUSTIBLE ACIDS. 



for base in solution. The urates of potash, soda, 

 lime, barytes, and strontian, formed in this way, 

 almost exactly resemble the uric acid itself in 

 appearance. Dr. Prout has shown that urate of 

 ammonia is the most soluble of all the urates. 

 This salt reddens vegetable blues like uric acid 

 itself; and 1 grain of it is soluble in 480 grains 

 of cold water. 



3. 11*25 grains of uric acid were exposed for 

 24 hours to a heat of about 400, upon a sand 

 bath : the acid was placed upon a watch glass, 

 over which another watch glass was inverted, 

 partly to prevent any accidental impurity, and 

 partly to prevent any of the acid from being dis- 

 sipated or sublimed without my knowledge. Some 

 water was seen to attach itself to the upper glass, 

 but in less than an hour all appearance of mois- 

 ture had vanished, and no farther sensible altera- 

 tion took place. The crystals, thus treated, being 

 weighed, were found to have lost 2*25 grains of 

 their weight, the colour was rather darker than 

 before this treatment, but no other alteration 

 could be perceived in the appearance of the 

 crystals. When treated with nitric acid, they 

 exhibited the very same phenomena as uric acid 

 which had not been exposed to heat. From this 

 experiment it appears, that crystallized uric acid 

 is composed of 



