Parameters, specification Appearance, clear colourless liquid Total acidity (as hno3) percentage by mass (min), 68% min. Specific gravity ( at 20* c), 1.4 Nitrous acid (as hno2) (max.), 5 ppm max Chlorides (as cl) percentage by mass (max.), 0.002 Sulphates(as h2so4) percentage by mass (max.), 1 ppm max. Residue on ignition (max.), 2 ppm max. Iron content (as fe) percentage by mass (max.), 1 ppm max. Lead content percentage by mass (max.), 1 ppm max. Platinum as pt, 0.5 ppm max. Palladium as pd, 0.5 ppm max. Arsenic content percentage by mass (max.), 2 ppm max.