The uppermost section acts as a funnel to feed the lower section. There is no direct path from the top to the middle bulb. Sufficient acid is poured in to fill the bottom section and flood the solid in the center bulb. The gas tap is closed. Gas is produced and the pressure builds up inside the bulb, forcing the acid down into the bottom bulb and up into the top one. When the liquid is forced out of the center bulb the generation of gas stops. The apparatus is now set up ready for use.
When gas is needed, the tap is turned on. The gas pressure in the center bulb is released. There is no extra pressure to hold the acid in the top bulb so it drops down to completely fill the bottom bulb and once more flood the solid.
When the gas tap is turned off, as the gas can no longer escape, the pressure again builds up, forcing the liquid back into the top bulb or reservoir. The build up of pressure ceases when all drops of acid left clinging to the solid have been used up.
In time, the acid grows weaker and the solid is used up. The chemicals need renewing. The acid is drained out by removing the bung from the lower bulb, after which the remaining solid can be taken out. This should be done in a fume cupboard to prevent the breathing of poisonous fumes. Because of its poisonous qualities and unpleasant smell of bad eggs, it is advisable to always keep a hydrogen sulfide Kipp's apparatus in the fume cupboard.
