Kipp's apparatus, also called Kipp generator, is an apparatus designed for preparation of small volumes of gases. It was invented around 1844 by the Dutch pharmacist Petrus Jacobus Kipp and widely used in chemical laboratories and for demonstrations in schools into the second half of the 20th century.
It later fell out of use, at least in laboratories, because most gases then became available in small gas cylinders. These industrial gases are much purer and drier than those initially obtained from a Kipp apparatus without further processing.
Design and operation
The apparatus is made of three vertically stacked cylinders, roughly resembling a snowman. The solid material (e.g., iron sulfide) is placed into the middle cylinder, the acid is put into the top cylinder. A tube extends from the top cylinder into the bottom cylinder. The middle cylinder has a tube with a stopcock attached, which is used to draw off the evolved gas. When the stopcock is closed, the pressure of the gas in the middle cylinder rises and expels the acid back into the top cylinder, until it is not in contact with the solid material anymore, and the chemical reaction stops.
The produced gas often requires further purification and/or drying, due to content of water vapor and possibly mist if the reaction is vigorous.
Examples for prepared gases and their educts
- Hydrogen from zinc flakes and hydrochloric acid or diluted sulfuric acid
- Carbon dioxide from pieces of marble (calcium carbonate) and hydrochloric acid
- Hydrogen sulfide from iron(II) sulfide and hydrochloric acid
- Acetylene from calcium carbide and water
- Methane from aluminium carbide and lukewarm water
- Chlorine from potassium permanganate, calcium hypochlorite, or manganese dioxide and hydrochloric acid
- Oxygen from calcium hypochlorite and hydrogen peroxide with a bit of nitric acid
- Nitric oxide from copper turnings and diluted nitric acid
A version of the apparatus can be used for reaction between two liquid precursors. A mercury trap has to be added as a check valve, and the middle bulb is filled with an inert porous material, e.g. pumice, onto which one of the precursors is dropped.
- Hydrogen chloride is prepared from hydrochloric acid and concentrated sulfuric acid
- Hydrogen sulfide from concentrated sodium sulfide solution and diluted sulfuric acid
- Sulfur dioxide from 40% solution of sodium metabisulfite and concentrated sulfuric acid
- Nitric oxide from ferrous chloride in hydrochloric acid and 20% solution of sodium nitrite
- Dinitrogen trioxide, aka nitrous anhydride, from 20% solution of sodium nitrite and concentrated sulfuric acid
For further reading
- Green, John Joseph (1860). Chemical Recreations: A Popular Manual of Experimental Chemistry (10 ed.). John Joseph Green. p. 616. Retrieved 2007-11-12.
- Sella, Andrea (November 2007). "Kipp's Apparaatus". Chemistry World: 81. Retrieved 2007-11-13.
- Kipp's apparatus - extensive explanation with pictures and references