Kipp's apparatus

Empty Kipp's apparatus, with stopcock and fermentation lock.
Drawing of a filled Kipp's apparatus.

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 chambers, roughly resembling a snowman. The solid material (e.g., iron sulfide) is placed into the middle chamber, the acid is put into the top chamber. A tube extends from the top chamber into the bottom chamber. The middle chamber 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 chamber rises and expels the acid back into the top chamber, until it is not in contact with the solid material anymore, and the chemical reaction stops.

Kipp generators only work properly in the described manner if the solid material is insoluble in the acid. They are usually made of glass, or sometimes of polyethylene.

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

For successful use in a Kipp's apparatus, the solid material has to be available in lumps large enough to stay on the retention plate without falling through its holes.

Generally, weak acidic gases can be released from their metal salts by dilute acids, and sometimes just with water:[1]

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.[3]

Further gas treatments

The prepared gas is usually impure, contaminated with fine aerosol of the reagents and water vapor. The gases may need to be filtered, washed and dried before further use.

Hydrogen can be washed from sulfane, arsine and oxygen with subsequent bubbling through solutions of lead acetate, silver nitrate, and alkaline pyrogallic acid.[4]

Acidic gases (e.g. hydrogen sulfide, hydrogen chloride, sulfur dioxide) can be dried with concentrated sulfuric acid, or with phosphorus pentoxide. Basic gases (e.g. ammonia) can be dried with calcium oxide, sodium hydroxide or soda lime.

Disposal of the gases can be done by burning the flammable ones (carbon monoxide, hydrogen, hydrocarbons), absorbing them in water (ammonia, hydrogen sulfide, sulfur dioxide, chlorine), or reacting them with a suitable reagent.[2]

Variants

Many variants of the gas production apparatus exist. Some are suitable for production of larger amounts of gases (Gay-Lussac and Verkhovsky), some for smaller amounts (Kiryushkin, U-tube).

A Döbereiner's lamp is a small modified Kipp's apparatus for production of hydrogen. The hydrogen is led over a platinum sponge catalyst, where it reacts with air oxygen, heats the catalyst and ignites from it, producing a gentle flame. It was commercialized for lighting fires and pipes. It's said that in 1820s over a million of the "tinderboxes" ("Feuerzeug") was sold.[5]

Further reading

References

  1. 1 2 Egon Wiberg; Nils Wiberg (2001). Inorganic Chemistry. Academic Press. pp. 267–. ISBN 978-0-12-352651-9.
  2. 1 2 László Erdey (22 October 2013). Gravimetric Analysis: International Series of Monographs in Analytical Chemistry. Elsevier. pp. 221–. ISBN 978-1-4832-2259-2.
  3. ↑ http://users.humboldt.edu/rpaselk/MuseumProject/Instruments/Kipp-Erdmann/GasCurrents.htm
  4. ↑ https://books.google.cz/books?id=qwLgBAAAQBAJ&pg=PA161&dq="kipp%27s+apparatus"&hl=en&sa=X&ved=0ahUKEwjJ6qPY-PfJAhUK8HIKHXYlC2UQ6AEIRjAJ#v=onepage&q=%22kipp's%20apparatus%22&f=false
  5. ↑ https://books.google.cz/books?id=eFXWBgAAQBAJ&pg=PA16&dq=%22kipp%27s+apparatus%22+methane&hl=en&sa=X&ved=0ahUKEwi9zMbo-ffJAhXiD3IKHZMWBy4Q6AEIJzAC#v=onepage&q=%22kipp's%20apparatus%22%20methane&f=false

External links

This article is issued from Wikipedia - version of the Wednesday, February 10, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.