"Coxe (1806) discussed applying milk, white eggs, water and opium in treating arsenic poisoned cases"[1][2] (footnotes at end of thread)
I've also found the book Poisoned Lives[3] which indicates that the reaction to arsenic varies depending on whether it was diluted with water. If the arsenic was ingested in large grains, it's likely much of it would pass through the digestive system unabsorbed. /4