Martin,
Just for the record and to dispell a common misconception:
Most of the uric acid found in blood is converted to urea within the liver.
Mamalian urine, when first expelled from the body may be mildly acidic but bacterial decomposition takes nitrogen from the atmosphere and forms ammonia (alkaline) which quickly evaporates, leaving a highly alkaline residue of anhydrous uric salts.
The ammonia has some bleaching action but it is the scorching effect of the alkaline salts that does the major damage.
John.
