Nothing yet about the song, but did find this rather terse comment about urine and gunpowder:
"... These ingredients are coarsely ground, and put in an iron pot, then moistened with water, alcohol, vinegar, or urine. Which liquid matters very little, since the objective is to extinguish any sparks. ..."
This is a quote from a discourse on gunpowder by an American "honorary fellow" at Exeter, Dr. James B. Calvert. His website, which is extensive, is a wealth of words on a mixture of subjects. If you want to get lost for awhile, try this: