What is "concentrated cash"? Do you have to dilute it down to standard issue bills before spending it? Someone hands you 5 lbs of gold, and have to barter with

What is "concentrated cash"? Do you have to dilute it down to standard issue bills before spending it? Someone hands you 5 lbs of gold, and have to barter with people to use it? "He didn't need the money. He wasn't sure he didn't need the gold." (an Isaac Asimov short story) > More suicidal people than not, would cease to be suicidal if ... I'm going to need to see a citation on this one.