In any chemical laboratory where analysis is carried out, there needs to be a supply of hydrogen sulfide gas which can be turned on and off at will. Usually when a gas is made in the laboratory, the apparatus has to be set up each time the gas is needed. Furthermore there is no way of switching the supply on and off. For hydrogen sulfide, prior to the modern use of thioacetamide, Kipp's apparatus overcame this problem. The same apparatus can also be used for supplying carbon dioxide or hydrogen on tap.
Although a regular supply of other gases may also be needed, these are the only three common gases for which the Kipp's apparatus can be used. This is because to produce other gases heating is required. This is out of the question in the Kipp's apparatus because it would shatter on heating. The gas flow is controlled by making gas only when a cold liquid is in contact with lumps of solid. Hydrogen sulfide, carbon dioxide, and hydrogen are all made in this way. When the liquid is drained away from the solid, the supply stops. No heating is needed to make them. They are made by the action of cold acids on pieces of solid. Broken sticks of ferrous sulfide are used for making hydrogen sulfide, marble chippings for carbon dioxide, and zinc granules for hydrogen.
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.
Related category LABORATORY EQUIPMENT
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