Liquid Hydrogen: Gas at 200 Atmospheres Cooled by Dry Ice and Liquid Air, then Expanded in a Regenerator Coil (Travers, 1901)

Put about 40 lb of commercial granulated zinc in a beer cask with a tap funnel, a delivery tube, an escape pipe into a vessel of water (safety valve) and a stoneware cock at the bottom to draw off spent acid. Run in dilute sulphuric acid. When the air is out, pass the gas through a wash-bottle of potassium permanganate into the gasometer (sheet iron, 6 ft high, 5 ft 6 in across, over water first saturated with hydrogen). Wash the gasometer out with hydrogen before collecting the main quantity. This takes five hours.

In the two or three days before, use the compressor to make liquid air with the Hampson liquefier and store it in vacuum vessels, about 8 litres in all. Then take the compressor apart and check the valves, springs and fibre packings. Remove the Hampson machine and connect the compressor through the cylinder of caustic potash to the hydrogen liquefier.

Four people are needed. Pack the vessel round coil A with solid carbonic acid and alcohol (-80 °C). Pour liquid air into chamber B and let it into chamber C, pumped down to 100 mm of mercury so it boils below -200 °C. Draw liquid air into vacuum vessel H and boil it under reduced pressure to chill the regenerator coil below -200 °C, then let it out and put vessels K and M (with a little liquid air) back in place.

Purge the air from the compressor: open cock a, run a few turns, stop and open cock rho; do this three or four times. Then raise the pressure. The first cylinder takes the gas to about 16 atm, with a little glycerol and water holding 5 % caustic soda as lubricant; the second takes it to about 200 atm. The water is separated out and the gas dried over lumps of solid caustic potash. Have it at 200 atm by the time the liquefier is cold.

Reconnect chamber C to the exhaust pump and let liquid air in slowly (a fall of the mercury in the vacuum gauge means too fast). Open the expansion valve with the milled nut; let the gas out through the water tank for a few moments to clear the air, then open cock i so it circulates back. Keep B and the coil-A vessel topped up. Watch the glycerol gauge for the flow and turn the milled nut slowly back and forth the whole time so it does not block. H coats with white solid air; open cock r now and then, and the liquid runs through a baize filter into K. Lift K out on its wire into a vessel with a little liquid air. About 10 % of the gas is lost per run.