> 1) It takes about three minutes per hive, handling dry (crystalline) acid, > as opposed to obviously more hazardous liquid formic. Oxalic acid is very hazardous in its dry form due to the risk of inhaling dust from it. Presumably, vaporising it is extremely hazardous. Once dissolved in water the hazard is removed. Safety datasheet here: http://ptcl.chem.ox.ac.uk/MSDS/OX/oxalic_acid_dihydrate.html Peter Edwards [log in to unmask]