I use a wide range of dyes in my work, as biological stains, and there is a persistent story which is circulated concerning one of the dyes, called Gentian Violet. It seems this dye was manufactured by a number of companies, but for unknown reasons, the product produced by a particular German company was far superior to that from any other manufacturer. Some representatives of an American dyestuffs company visited the German plant to observe their production methods. As they passed by one of the production areas, they happened to see a workman urinating in the vat where the dye was being produced, rather than taking the time to walk to the facilities at the other end of the plant. Well, it turned out that was the magic ingredient. Specifically, the factor which made the difference was nitrogen; and urea, which is found in mammalian urine, was a ready source of nitrogen. Urea is still used today in the manufacture of that dye and several others - only now it is added in a more sanitary manner. Paul M.