ERROR opening https://cactus.nci.nih.gov/chemical/structure/InChI%3DInChI%3D1S/Ca.Mg.2O/q2%2A%202%3B2%2A-2/file?format=sdf&get3d=True  -- InChI%3DInChI%3D1S/Ca.Mg.2O/q2%2A%202%3B2%2A-2 could not be loaded.