... > SECTION VI - PRODUCTS OF THE CHEMICAL OR ALLIED INDUSTRIES > CHAPTER 28 - INORGANIC CHEMICALS; ORGANIC OR INORGANIC COMPOUNDS OF PRECIOUS METALS, OF RARE-EARTH METALS, OF RADIOACTIVE ELEMENTS OR OF ISOTOPES > I. CHEMICAL ELEMENTS > 2804 Hydrogen, rare gases and other non-metals > Hydrogen > electrolytic hydrogen > solar electrolytic hydrogen