Credit: Diego Sanz; (inset) iStockphoto BALTIMORE, MARYLAND—There's nothing like suddenly going blind to spoil a good happy hour. Alcoholic beverages tainted with poisonous methanol are a scourge of the developing world, causing blindness and even death. The dangerous drinks can come from botched batches of home-distilled liquor, but they often have a more sinister origin; criminal gangs will cut standard alcohols with methanol and sell the resulting concoctions to unassuming customers for inflated profits. Because adding methanol doesn't change the drink's flavor, color, or smell, there's no easy way to tell if the brew you're about to imbibe could...