Having metal ions in your conc. sulfuric acid can give real problems in some reactions.
What kind of problems? Would this cause problems with hydrolisis using 15% h2so4(epoxide->mdp2p)?
Maybe H2SO4 density is like a h2o at 4 degC type thing?
As far as I know ONLY H2O has this density anomaly at 4 °C. Somebody correct me, in case that´s wrong, please.