I am reminded of the story from back in the days of alchohol prohibition. A guy was speaking to a crowd from a platform about the evils of drink. To demonstrate, he gets a jar of live wiggly worms and holds it out for the audience to see. Then he gets a bottle of whiskey and tips it over the worms. After a short pause, he holds the jar up and the audience can see the worms are floating and dead.
"What does that teach you?" he asks. A bum in the audience yells out "if you've got worms, drink whiskey".
Likewise, putting 65% FA into a small jar of liquid containing yeast, does not equate to vaporising one gram of the different product oxalic, into a beehive. A more honest experiment would be to swab a beehive prior to treatment. Then vaporise a gram of oxalic into the hive. Leave perhaps a month for all traces of oxalic to be gone, and do another swab.